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JP2010166584

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DESCRIPTION JP2010166584
A method suitable for selecting a configuration of a car audio system is provided. The method
comprises the steps of generating an acoustic signal from at least one loudspeaker located at a
candidate loudspeaker location of the vehicle and recording transfer functions for the generated
acoustic signal at a plurality of listening locations of the vehicle. Determining a candidate
configuration of the audio system of the vehicle, modifying the transfer function based on the
candidate configuration to generate a predictive transfer function, at least one of the predictive
transfer functions at a plurality of listening locations of the vehicle Analyzing statistically over
frequency and selecting a configuration based on the statistical analysis. [Selected figure] Figure
5
System and method for audio system configuration
[0001]
2. Detailed Description of the Invention Field of the Invention (1. RELATED APPLICATIONS
[0001] This application claims the entire benefit of US patent application Ser. No. 11336/643
P03059 USV1, entitled “Optimization of Low Frequency in the Room,” filed Oct. 9, 2003, the
entire contents of which are incorporated herein by reference. Claim priority to US Provisional
Application No. 60 / 509,799.
[0002]
No. 11336/433 P03060US, entitled "Statistical Analysis of Audio System Configuration
Candidates," filed Oct. 10, 2003, the entire contents of which are incorporated herein by
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1
reference. Claims priority to patent application 10 / 684,222.
[0003]
No. 11336/434, entitled “System for Selecting Correction Factors for an Audio System,” filed
Oct. 10, 2003, the entire contents of which are incorporated herein by reference. P03060 US,
claims priority to US patent application Ser. No. 10 / 684,152.
[0004]
No. 11336/435, entitled "System for Selecting a Speaker Position in an Audio System," filed Oct.
10, 2003, the entire contents of which are incorporated herein by reference. P03061 US, claims
priority over US patent application Ser. No. 10 / 684,043.
[0005]
No. 11336/545 P03121, entitled "System for Configuring an Audio System", filed Oct. 10, 2003,
the entire contents of which are incorporated herein by reference. Claims priority to patent
application 10 / 684,208.
[0006]
(2.
TECHNICAL FIELD The present invention relates generally to improving sound system
performance in a given space.
The invention relates in particular to providing a more enjoyable listening experience by
improving the frequency response performance to one or more listening places in a given area.
[0007]
Background of the Invention (3.
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2
Related Art) A sound system generally includes a loudspeaker that converts an electrical signal to
an acoustic signal.
These loudspeakers may include one or more transducers that generate a range of acoustic
signals, such as high, medium and low frequency signals. One type of loudspeaker is a subwoofer,
which may include a low frequency converter to generate a low frequency signal.
[0008]
A sound system may generate acoustic signals in various listening environments. Examples of
listening environments include, but are not limited to, home listening rooms, home theaters,
cinemas, concert halls, vehicle interiors, recording studios and the like. In general, the listening
environment comprises one or more listening places for one or more persons to hear the
acoustic signal generated by the loudspeaker. The listening location may be a sitting position,
such as a piece of tea in a home theater environment, or a standing position, such as where a
conductor stands in a concert hall.
[0009]
Acoustic signals, including low, medium and / or high frequency signals at the listening location
may be affected by the listening environment. Depending on where the listener is located in the
room, the loudness of the sound may change depending on the respective tone. This is especially
true for low frequencies in smaller home size rooms, as the loudness (measured in amplitude) of
a particular tone or frequency is artificially increased or reduced. Low frequencies may be
important to enjoy music, movies, and most other forms of audio entertainment. In the home
theater example, room boundaries, including walls, curtains, furniture, furnishings, etc., can affect
the acoustic signal in progress from the loudspeakers to the listening location.
[0010]
The acoustic signal heard at the listening location may be measured. One measure of an acoustic
signal is a transfer function, which may measure characteristics of the acoustic signal, including
single frequency, discrete numbers of frequencies, or amplitude and / or phase in a frequency
range. The transfer function may measure various ranges of frequencies.
09-05-2019
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[0011]
The amplitude of the transfer function indicates the loudness of the sound. In general, the
amplitude of a single frequency or frequency range is measured in decibels (dB). The amplitude
deviation may be expressed as a positive or negative decibel value with respect to a
predetermined target value. When considering the amplitude deviation at a plurality of
frequencies, the target curve may be flat or may have an arbitrary shape. The amplitude response
is the magnitude of the amplitude deviation from the target value at one or more frequencies.
The closer the amplitude value measured at the listening location is to the target value, the better
the amplitude response. Deviations from the target value reflect the changes that the acoustic
signal has in the acoustic signal due to interaction with the room boundaries. The peak
represents the increase of the amplitude deviation from the target value, and the dip represents
the decrease of the amplitude deviation from the target value.
[0012]
These deviations in the amplitude response may vary depending on the frequency of the acoustic
signal reproduced by the subwoofer, the location of the subwoofer, and the location of the
listener. The low frequencies recorded on recording media such as soundtracks or movies may
not be heard by the listener, but low frequencies distorted by room boundaries may be heard by
the listener. In this way, the room can alter the acoustic signal reproduced by the subwoofer and
adversely affect the frequency response performance, such as the low frequency characteristics
of the sound system.
[0013]
Many techniques attempt to reduce or eliminate the amplitude deviation at a single listening
location. One such technique involves global equalization, which filters all subwoofers in the
system uniformly. In general, the amplitude is measured at multiple frequencies at a single
location in the room. For example, amplitude measurements may be performed at 25, 45, 65, and
80 Hz to determine the amplitude deviation for each measured frequency. As a global
equalization, the filters may be applied to each subwoofer to reduce the +10 dB deviation at 65
Hz. Thus, in global equalization, either reduce the amplitude of the frequency range where the
deviation from the target value is positive or increase the power of the subwoofer in the
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frequency range where the negative deviation from the target value is largest The amplitude
deviation may be reduced by However, only the amplitude deviation at a single listening location
can be corrected by global equalization.
[0014]
Another technique for reducing or eliminating amplitude deviations is spatial averaging. Spatial
averaging, a more sophisticated equalization method, calculates the average amplitude response
for multiple listening locations and then implements equalization uniformly for all subwoofers in
the system. However, spatial averaging can only correct for a single "average listening location"
that does not actually exist. Thus, the use of spatial averaging techniques can significantly
improve low-pass performance at some listening locations but not so much at others. In addition,
attempting to equalize to a single location may cause problems. Although the peak at the average
listening location may be reduced, trying to reduce dips requires the sound output from the
subwoofer to be increased significantly, reducing the maximum sound output of the system, to
other areas of the room Large peaks may occur.
[0015]
Besides equalization and spatial averaging, conventional techniques have attempted to improve
the sound quality at a particular listening location by loudspeaker placement. One technique
analyzes standing waves to optimize the placement of loudspeakers in a room. Standing waves
may be generated by the interaction of the acoustic signal with the room boundaries, generating
modes with large amplitude deviations in the low frequency response. A mode that depends only
on the single dimension of the room is called the axis mode. The mode determined by the two
dimensions of the room is called tangent mode, and the mode based on all three dimensions of
the room is called oblique mode.
[0016]
FIG. 1 is a diagram representing the first four axial modes for a single dimension of a room at an
instant. The maximum value of the sound pressure exists at the room boundary (ie, at the two
ends in FIG. 1). The point at which the sound pressure falls to its minimum is generally called
"null". If there is no modal damping, the sound pressure at the null point drops to zero. However,
in most actual rooms, the response dip at the null point is in the range of -20 dB. As shown in
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FIG. 1, at various locations in the room, the standing waves may peak and dip, so large amplitude
deviations may occur depending on where the listener is. Thus, when listener C is at the 30 Hz
peak position, any 30 Hz frequency generated by the subwoofer sounds much larger than
intended. Conversely, when the listener D is in the 30 Hz dip position, any 30 Hz frequency
generated by the subwoofer sounds much softer than intended. In either case, neither the
acoustic signal reproduced by the subwoofer nor the acoustic signal pre-recorded on the
recording medium is matched.
[0017]
There are several ways to reduce standing waves in a given listening room by locating the
loudspeakers. One way is to place the subwoofer at the null point of the standing wave. In
particular, the loudspeakers in the room and the particular listening location may be carefully
selected so that the transfer function at the particular listening location is relatively smooth. A
possible combination of loudspeaker position and listener position is shown in FIG. 2 when the
first four axis modes are along the longitudinal direction of the room. The loudspeaker may be
placed at the null point of the third mode while this particular listening location is placed away
from the maxima and null positions of the first, second and fourth modes. As a result, if only
these modes are resonant modes in the room, the transfer function at this particular listening
location should be relatively smooth. However, in order to reduce the effects of standing waves in
the listening environment, this method focuses on only a single specific listening location and
does not consider multiple listening locations or listening areas. In fact, the prediction by this
method is unreliable by the presence of other axis modes, tangent modes and oblique modes in
the room.
[0018]
Another way is to place multiple subwoofers in a "cancel mode" configuration. By placing
multiple loudspeakers symmetrically in the listening room, destructive interference and
constructive interference may be used to reduce standing waves. However, the “cancel mode”
symmetric configuration assumes an ideal room (ie, a room that is dimensionally and acoustically
symmetrical), including differences in room shape and furnishings. The characteristics of the
room are not taken into account. Furthermore, the symmetrical placement of the loudspeakers
may not be a realistic or desirable configuration for a particular room setting.
[0019]
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Another audio system construction technique to reduce amplitude deviation is to use
mathematical analysis. One such mathematical analysis simulates standing waves in a room
based on the data in the room. For example, room dimensions such as room length, width and
height are input, and based on the input data, various algorithms predict the placement position
of the subwoofer. However, this mathematical method does not take into account the acoustic
characteristics of the room's furniture, furnishings, configurations etc. For example, when the
surface of the inner wall is a masonry, the effect on hearing may be very different compared to a
wooden frame wall. In addition, this mathematical method can not effectively compensate for a
partially enclosed room, and may be computationally expensive if the room is not rectangular.
[0020]
Another mathematical method analyzes the transfer functions heard at each listening location
and determines the equal transfer functions heard at each listening location. FIG. 3 shows an
example of a scenario in which a plurality of subwoofers and a plurality of receivers are disposed
indoors. Reference symbol I is a signal input to the system. The transfer functions of the
loudspeakers / rooms from the loudspeaker 1 and the loudspeaker 2 to the two receiver
positions in this room are denoted by H11 to H22, R1 and R2 being the resulting at two receiver
positions The transfer function is shown. Since there is a transmission path to each receiver for
each sound source, the number of transfer functions in this example is four. Modified signals
may be added, assuming that electrical corrections represented by M1 and M2 are possible for
the signals sent to each loudspeaker. Here, M is a frequency-dependent or independent complex
corrector. To illustrate the complexity of this mathematical solution, linear time-invariant systems
in this frequency domain are solved by the following equation:
[0021]
R1 (f) = 1H11 (f) M1 (f) + 1H21 (f) M2 (f) (1) R2 (f) = 1H12 (f) M1 (f) + 1H22 (f) M2 (f) where all
The transfer functions and modifiers are, of course, complex transfer functions and complex
modifiers. Since this is recognized as a set of simultaneous linear equations, it can be expressed
more simply in matrix form as follows.
[0022]
Or simply: HM = R (3) where it is assumed that the input I is 1 (unity).
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[0023]
A general optimization goal is to make R equal to one, ie to make the signals at all receiver
locations equal to one another.
If both Rl and R2 are equal to one, then R may be considered as an objective function. Solving
equation (3) for M (corrector for audio system), M = H-1, i.e. the inverse of H. Since H is
frequency dependent, the solution for M needs to be calculated for each frequency. However, the
value of H may be uncomputed or unrealistic to implement (eg, the gain for some loudspeakers
may be unrealistically high for some frequencies).
[0024]
Conventional approaches have attempted to find the best solution that can be calculated, such as
the one with the least error, since accurate mathematical solutions are not always sought. The
error function defines how close any particular configuration is to the desired solution, with the
smallest error representing the best solution. However, this mathematical method requires a
huge amount of computational energy, but only solves for two-parameter solutions. Solving
acoustic problems that test more parameters is even more difficult.
[0025]
Accordingly, there is a need for a system for accurately determining the configuration of an audio
system that improves the audio performance of one or more listening locations in a given space.
[0026]
SUMMARY OF THE INVENTION The present invention provides the following items.
[0027]
1.
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A method of selecting a configuration of an in-vehicle audio system, comprising: generating an
acoustic signal from at least one loudspeaker disposed at a candidate loudspeaker position of the
vehicle; Recording at the listening location of the vehicle, determining configuration candidates
for the audio system for the vehicle, modifying the transfer function based on the configuration
candidates to generate a predictive transfer function, and listening to the plurality of vehicles.
Analyzing statistically over at least one frequency of a predicted transfer function for the
location, and selecting a configuration based on the statistical analysis.
[0028]
2.
The method according to claim 1, further comprising the step of configuring the in-vehicle audio
system based on the selected configuration.
[0029]
3. An in-vehicle audio system configured based on the configuration according to Item 1.
[0030]
4. A machine readable medium having software for causing a machine to perform a method
comprising: instructions for generating an acoustic signal from at least one loudspeaker located
at a candidate loudspeaker location of a vehicle; Instructions for recording the transfer function
at multiple listening locations of the vehicle, instructions for determining a candidate
configuration of the vehicle's audio system, and modifying the transfer function based on the
configuration candidate to generate a predictive transfer function A machine readable medium
comprising: instructions for: analyzing statistically over at least one frequency of a predictive
transfer function for a plurality of listening locations of a vehicle.
[0031]
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5. A method of selecting a configuration of an in-vehicle audio system comprising: recording a
transfer function at at least one listening location in an audio system for a vehicle; determining a
candidate configuration of an audio system for a vehicle Correcting the transfer function based
on the configuration candidates to generate a prediction transfer function, statistically analyzing
the prediction transfer function, selecting a configuration for the vehicle based on the statistical
analysis An in-vehicle audio system including a configuration selected based on a method
including:
[0032]
6. 6. The method of claim 5, further comprising configuring the in-vehicle audio system based
on the selected configuration.
[0033]
7. An in-vehicle audio system configured based on the configuration according to Item 5.
[0034]
8. Recording the transfer function at at least one listening location in the audio system for the
vehicle; determining a candidate configuration of the audio system for the vehicle; and
generating the predictive transfer function based on the candidate configuration. A vehicle
comprising: a configuration selected based on a method including: correcting a transfer function;
statistically analyzing a predictive transfer function; selecting a configuration for the vehicle
based on the statistical analysis Audio system inside.
[0035]
9. A machine readable medium having software for causing a machine to perform a method,
instructions for storing a transfer function recorded at at least one listening location in an audio
system for a vehicle, an audio system in a vehicle An instruction for determining a configuration
candidate for the step, an instruction for correcting the transfer function based on the
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configuration candidate to generate a predictive transfer function, an instruction for statistically
analyzing the predictive transfer function, Machine readable media.
[0036]
10. A method of selecting at least one correction factor for an in-vehicle audio system
comprising: generating an acoustic signal from at least one loudspeaker located at a candidate
loudspeaker location for a vehicle; Recording a transfer function for the signal at a plurality of
listening locations of the vehicle; modifying the transfer function based on the correction factor
candidate to generate a predictive transfer function; Analyzing statistically over at least one
frequency and selecting a correction factor based on the statistical analysis.
[0037]
11. 11. The method of item 10, further comprising the step of configuring an audio system in
a vehicle using the selected correction factor.
[0038]
12. 11. The method of item 10, wherein the at least one correction factor comprises delay,
gain and / or filtering.
[0039]
13. An in-vehicle audio system configured based on the configuration according to Item 10.
[0040]
14. Generating an acoustic signal from at least one loudspeaker located at a candidate
loudspeaker location for the vehicle; recording a transfer function for the generated acoustic
signal at a plurality of listening locations of the vehicle; a predictive transfer function Modifying
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the transfer function based on the correction factor candidates to generate a statistical analysis
of at least one frequency of the predicted transfer function for the plurality of listening locations
of the vehicle; An in-vehicle audio system comprising a configuration selected based on a method
comprising: selecting a correction factor for the system.
[0041]
15. 15. Method according to item 14, wherein the at least one correction factor comprises
delay, gain and / or filtering.
[0042]
16. A machine readable medium having software for causing a computer to perform the
method comprising: instructions for generating an acoustic signal from at least one loudspeaker
disposed at a candidate loudspeaker location for a vehicle; Instructions for recording transfer
functions for signals at multiple listening locations of the vehicle, instructions for modifying the
transfer functions based on the correction factor candidates to generate a predictive transfer
function, and for multiple listening locations of the vehicle A machine readable medium
comprising: instructions for statistically analyzing at least one frequency of a predictive transfer
function; and instructions for selecting a correction factor based on the statistical analysis.
[0043]
17. A method for selecting at least one loudspeaker position from loudspeaker position
candidates in an audio system for a vehicle, comprising the steps of: determining a loudspeaker
position candidate of a vehicle; Generating an acoustic signal from one loudspeaker; recording
transfer functions for the generated acoustic signal at a plurality of listening locations; and
generating a transfer function based on the candidate loudspeaker positions to generate a
predictive transfer function. Modifying at least one of: at least one of statistically analyzing the
statistical transfer over at least one frequency of the predicted transfer function for the plurality
of listening locations of the vehicle; and selecting at least one loudspeaker location of the vehicle
based on the statistical analysis. How to include it.
[0044]
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18. An in-vehicle audio system, wherein at least one loudspeaker in the audio system is
configured based on the at least one loudspeaker position selected in item 17.
[0045]
19. A machine readable medium having instructions for causing a machine to perform a
method comprising: instructions for determining candidate loudspeaker positions in an audio
system for a vehicle; at least one located at candidate loudspeaker positions for a vehicle
Instructions for generating an acoustic signal from the loudspeaker, instructions for recording
transfer functions for the generated acoustic signal at a plurality of listening locations, and
transmission based on candidate loudspeaker positions to generate a predictive transfer function
A machine readable medium comprising: instructions for modifying a function; and instructions
for statistically analyzing at least one frequency of a predicted transfer function for a plurality of
listening locations of a vehicle.
[0046]
20. A method of selecting a speaker for an in-vehicle audio system, comprising the steps of:
recording a transfer function at at least one listening location of the vehicle; Correcting the
transfer function based on the speaker number candidate, statistically analyzing the prediction
transfer function, and selecting the number of speakers for the vehicle from the speaker number
candidate based on the statistical analysis How to include it.
[0047]
21. A machine readable medium having software for causing a computer to execute a method
comprising: instructions for recording at least one vehicle speaker number candidate; and
instructions for recording a transfer function at at least one listening location of a vehicle. A
machine readable medium comprising: instructions for modifying a transfer function based on
the number of loudspeakers to generate a predicted transfer function; and instructions for
statistically analyzing the predicted transfer function.
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[0048]
22. A method of selecting at least one speaker type for a vehicle audio system including a
plurality of speakers and at least one listening location, comprising the steps of: determining a
speaker type candidate for the vehicle; Arranging the speaker position candidate and recording
the transfer function at a listening place of the vehicle; correcting the transfer function based on
the speaker type candidate and the speaker position candidate to generate the prediction transfer
function; And v. Analyzing the function statistically and selecting at least one speaker type for the
vehicle based on the statistical analysis.
[0049]
23. A machine readable medium having software for causing a computer to execute a method,
comprising: instructions for determining speaker type candidates in a vehicle; An instruction for
recording the function, an instruction for correcting the transfer function on the basis of the
speaker type candidate and the speaker position candidate to generate the prediction transfer
function, and an instruction for statistically analyzing the prediction transfer function And
machine readable media.
[0050]
24. An audio system comprising at least one crossover filter, the steps of: generating an
acoustic signal from at least one loudspeaker located at a candidate loudspeaker location;
Recording, modifying the transfer function based on the crossover filter candidate to generate a
predictive transfer function, statistically analyzing over at least one frequency of the predictive
transfer function for a plurality of listening locations for the vehicle An audio system comprising
the steps of: selecting a crossover filter for an audio system based on statistical analysis; and
selecting a crossover filter based on a method including:
[0051]
25. 24. Audio system according to item 24, wherein the audio system is in a vehicle.
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[0052]
26. The audio system according to Item 25, comprising a plurality of speakers, wherein a
crossover filter associated with each speaker is selected based on the method.
[0053]
27. The audio system according to item 24, wherein the crossover filter candidate changes
based on the order of the filter and the 3 dB down point.
[0054]
28. A method of selecting a crossover filter for an audio system, comprising the steps of:
generating an acoustic signal from at least one loudspeaker located at a candidate loudspeaker
location; Recording at: correcting the transfer function based on the crossover filter candidate to
generate a predictive transfer function; statistically over at least one frequency of the predictive
transfer function for a plurality of listening locations for the vehicle. And D. analyzing and
selecting a crossover filter for the audio system based on statistical analysis.
[0055]
The present invention is a system for configuring an audio system for a given space, such as a
room or the interior of a vehicle. The system may analyze any variable or parameter of the audio
system configuration that affects the transfer function at a single listening location or multiple
listening locations. Examples of parameters include loudspeaker position, number of
loudspeakers, loudspeaker type, listening location, correction factors (eg, filtering (one example is
parametric equalization), frequency independent gain and delay), and crossovers There is a filter.
[0056]
The system provides statistical analysis of the prediction transfer function. This statistical
analysis may be used to configure an audio system intended for a single listener or multiple
09-05-2019
15
listeners, eg for single values or multiple parameters for single parameters in the audio system.
Multiple values may be selected. Measurement of the transfer function including amplitude and
phase may be performed at a single listening location or at multiple listening locations. The
transfer function may include raw data measured by placing loudspeakers at candidate
loudspeaker locations and recording the transfer function using a microphone or other acoustic
measurement device at the listening location. This transfer function may then be modified based
on audio system configuration candidates, such as parameter value candidates. Examples of
parameter value candidates include a loudspeaker position candidate, a loudspeaker number
candidate, a loudspeaker type candidate, a correction coefficient value candidate, and / or a
crossover filter value candidate. The modified transfer function may represent a predicted
transfer function for the configuration candidate. Next, at least a portion of the predicted transfer
function for a single listening location or multiple listening locations may be analyzed
statistically, such as, for example, the amplitude or the amplitude within a particular frequency
band. This statistical analysis may represent particular metrics such as flatness, match, efficiency,
smoothness of the prediction transfer function. An audio system may be configured based on this
statistical analysis. For example, based on this statistical analysis, values for one or more
parameters may be selected, such as parameters in a predictive transfer function that maximizes
or minimizes a particular metric. By this method, the configuration of the audio system may be
improved or optimized for each listening location. If the space is inside a vehicle, one or more
parameters selected based on this statistical analysis may be used to configure an audio system
for the vehicle. If the space is a room, one or more parameters selected based on this statistical
analysis may be used to configure the audio system for the room.
[0057]
There are many types of statistical analysis that can be performed using predictive transfer
functions. The first type of statistical analysis may indicate the degree of agreement of the
prediction transfer function across multiple listening locations. When equalizing the system,
examples of the first type include mean spatial variation, mean spatial standard deviation, mean
spatial envelope (ie, minimum and maximum), and mean spatial maximum. The second type of
statistical analysis may measure the flatness of the prediction transfer function. Examples of the
second type include variation of spatial average, standard deviation of spatial average, envelope
of spatial average, and variation of spatial minimum. A third type of statistical analysis may
measure the seat-to-seat difference in the total sound pressure level relative to the predicted
transfer function. Examples of the third type include mean level variation, mean level standard
deviation, mean level envelope, and mean level maximum mean. Statistical analysis may provide
a metric of differences, such as degree of match, flatness, or sound pressure level differences, so
that configurations can be selected to minimize or maximize the metric (eg, increase flatness) .
09-05-2019
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[0058]
A fourth type of statistical analysis examines the efficiency of the predictive transfer function at a
single listening location or multiple listening locations. In fact, this statistical analysis may be a
measure of the efficiency of the sound system for a particular frequency, frequency group or
frequency range at a single listening location or multiple listening locations. An example of the
fourth type is acoustic efficiency. In the case of an audio system having a single listening
location, the average level divided by the total drive level for each loudspeaker may be measured
by acoustic efficiency. For audio systems with multiple listening locations, the average total level
divided by the total drive level for each loudspeaker may be measured by acoustic efficiency. The
acoustic efficiency for the predictive transfer function may be examined to select the
configuration with the higher or the highest acoustic efficiency for the predictive transfer
function.
[0059]
A fifth type of statistical analysis examines the output of a predictive transfer function at a single
listening location or multiple listening locations. This statistical analysis may be a measure of the
sound system's raw output for a particular frequency, frequency group, or frequency range at a
single listening location or multiple listening locations. In the case of an audio system with a
single listening location, an example of statistical analysis to examine the output is average level.
In the case of an audio system having multiple listening locations, an example of a statistical
analysis examining the output is the average overall level. A sixth type of statistical analysis
examines the flatness of the predicted transfer function at a single listening location. This
statistical analysis may analyze fluctuations in the prediction transfer function at a single
listening location, such as amplitude fluctuations or amplitude standard deviations.
[0060]
The system may include loudspeaker location, number of loudspeakers, loudspeaker type,
correction factor, listening location, crossover filter, or a combination of these systems in an
audio system having a single listening location or multiple listening locations. It also provides a
method to select For example, loudspeakers may be arranged at a large number of position
candidates in a predetermined space. The invention includes a system for selecting a loudspeaker
position for a given space. The transfer function at a single listening location or multiple listening
09-05-2019
17
locations may be measured by placing loudspeakers at candidate loudspeaker locations and
recording the transfer function at a single listening location or multiple listening locations. This
transfer function may then be modified based on the candidate loudspeaker locations to generate
a predictive transfer function. For example, transfer functions may be combined based on various
combinations of loudspeaker position candidates to generate a predictive transfer function. The
predictive transfer function may be analyzed statistically to indicate certain aspects of the
predictive transfer function, such as flatness, match, efficiency, and the like. The choice of
loudspeaker position may be based on a predictive transfer function that is indicative of the
desired modality or modality set.
[0061]
As another example, the predetermined space may be a space in which various numbers of
loudspeakers may be arranged for the audio system. The invention includes a system for
selecting the number of loudspeakers for an audio system in a given space. The transfer function
for a single listening location or multiple listening locations in the audio system may be modified
based on the candidate loudspeaker number. For example, to analyze candidate combinations of
loudspeakers equal in number to one of the candidate loudspeakers, a predictive transfer
function may be generated by combining the transfer functions. The prediction transfer function
may be analyzed statistically to indicate certain aspects of the prediction transfer function, such
as flatness, match, efficiency, and the like. The selection of the number of loudspeakers may be
based on a predictive transfer function that indicates the desired modality or modality set. The
selected number of loudspeakers may then be implemented in a particular audio system, such as
an in-vehicle audio system.
[0062]
As yet another example, the loudspeakers may differ by quality or quality group. For example,
the loudspeakers may differ depending on the radiation pattern (eg, monopolar or bipolar). As
another example, the loudspeakers may differ by switching polarity. The present invention
includes a system for selecting loudspeaker types or types for an audio system having a single
listening location or multiple listening locations. The transfer function may be measured by
placing different types of loudspeakers on the loudspeaker position candidate and recording the
transfer function. For example, various loudspeakers may be placed at each loudspeaker location
candidate and transfer functions may be recorded at each listening location. This transfer
function may be modified based on the type of loudspeaker. For example, various combinations
of loudspeaker combinations may be analyzed by combining transfer functions to generate a
09-05-2019
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predictive transfer function. By analyzing these prediction transfer functions statistically, it is
possible to show particular aspects such as flatness, agreement, and efficiency of the prediction
transfer functions. The choice of loudspeaker type or type group may be based on a predictive
transfer function indicative of the modal or modal set of interest. This type or type of
loudspeaker may then be implemented in a particular audio system, such as a car audio system.
[0063]
Correction factors may be applied to this audio system. Correction factors may include, but are
not limited to, delay, gain, amplitude, or filtering. These correction factors may apply to a
particular frequency range (such as low, medium or high frequency) and may also apply to
signals to one or more speakers in an audio system. Furthermore, these correction factors may
be temporary (such as filtering or delaying to change the phase) or non-temporary. The system
includes the selection of one or more correction factors for the audio system in a given space.
The prediction transfer function may be generated by correcting the transfer function for the
listening location with the correction coefficient candidate. The prediction transfer function may
be analyzed statistically to indicate certain aspects of the prediction transfer function, such as
flatness, match, efficiency, and the like. The choice of correction factor may be based on a
prediction transfer function that indicates the modal or modal set of interest. These correction
factors may then be implemented in a particular audio system, such as a car audio system.
[0064]
The audio system may include multiple listening location candidates. The system includes
selection of one or more listening locations from the plurality of listening location candidates.
The transfer function for candidate listening places may be recorded. A predictive transfer
function may be generated by modifying these transfer functions with audio system parameter
candidates, such as loudspeaker position candidates, speaker type candidates, correction factor
candidates, and / or crossover filters. The prediction transfer function may be analyzed
statistically to indicate certain aspects of the prediction transfer function, such as flatness, match,
efficiency, and the like. The choice of the single or multiple listening locations may be based on a
predictive transfer function that indicates the modalities or modal sets desired.
[0065]
09-05-2019
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Crossover filters may be applied to this audio system. Crossover filters may be associated with
one or more speakers. For example, if the speaker is to operate in a particular frequency range,
the filter may be selected so that the speaker operates in the desired range. Filters have different
characteristics, for example, filter type (for example, low pass filter, high pass filter, notch filter,
band pass filter, or a combination of such filters), 3 dB downpoint, filter order and so on. The
present invention involves the selection of crossover filter characteristics for a given space, such
as a vehicle. Based on the candidate values of the crossover filter, the transfer function for one or
more listening locations in the audio system may be modified. The prediction transfer function
may be analyzed statistically to indicate certain aspects of the prediction transfer function, such
as flatness, match, efficiency, and the like. The selection of characteristics such as the 3 dB points
of the crossover filter, the filter order, etc. may be based on a prediction transfer function that
indicates the desired modality or modality set. The selected crossover filter may then be used in
an audio system, such as a vehicle audio system.
[0066]
Other systems, methods, features, and advantages of the present invention will be or become
apparent to one with skill in the art upon examination of the following figures and detailed
description. It is intended that all such additional systems, methods, features and advantages be
included within this description, be within the scope of the present invention, and be protected
by the following claims.
[0067]
FIG. 1 is a diagram representing the first four axial modes for a single dimension of a room at an
instant. FIG. 2 is a diagram representing the first four-axis mode shown in FIG. 1, the position of
the loudspeaker, and the positions of the listener (Niconiko badge) and two additional listening
places 1 and 2; FIG. 3 is an example of a scenario in which there are multiple subwoofers and
multiple receivers in a room. FIG. 4 shows a room with multiple subwoofer location candidates,
multiple listening locations, and a sound system. FIG. 5 shows an example sound system 500, a
measuring device 520 and a computing device 570. FIG. 6 is a flow chart of a scheme for
improving the low frequency characteristics of the sound system. FIG. 7 is an expanded block
diagram of block 602 of FIG. 6 illustrating the selection of sound system parameters. FIG. 8 is an
expanded block diagram of block 604 of FIG. 6 showing the input of the transfer function. FIG. 9
is an expanded block diagram of block 606 of FIG. 6 showing modification of the transfer
function. FIG. 10 is a table of transfer functions and calculations to illustrate various statistical
analyzes that may be performed at block 608 of FIG. FIG. 11 is an expanded block diagram of
09-05-2019
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block 608 of FIG. 6 illustrating statistical analysis of acoustic efficiency and mean spatial
variation. FIG. 12 is an expanded block diagram of block 608 of FIG. 6 illustrating statistical
analysis of acoustic efficiency and spatial average variations. FIG. 13 is a table for explaining
solutions for selected parameters, which are generated in response to statistical analysis. FIG. 14
is an expanded block diagram of block 612 of FIG. 6 implementing the selected solution values
into the sound system. FIG. 15 is a layout example of the listening room of Example 1. FIG. 16 is
a graph showing the low frequency characteristics of the listening room of Example 1 without
low frequency optimization. FIG. 17 is a graph showing the listening room predicted low
frequency characteristics of Example 1 in which low frequency optimization was performed. FIG.
18 is a layout example of the dedicated home theater system of Example 2. FIG. 19 is a graph
showing the low frequency characteristics of the dedicated home theater system of Example 2
without low frequency optimization. FIG. 20 is a graph showing the predicted low-pass
characteristics of the dedicated home theater system of Example 2 with low frequency
optimization. FIG. 21 is a layout example of the family room home theater system of Example 3.
FIG. 22 is a graph showing the low frequency characteristics of the family room home theater
system of Example 3 without low frequency optimization and with only the two front subwoofers
(subwoofers 1 and 2 shown in FIG. 21) active. It is.
FIG. 23 is a graph showing the predicted low-pass characteristics of the family room home
theater system of Example 3 with low frequency optimization applied to the front two
subwoofers (subwoofers 1 and 2 shown in FIG. 21). FIG. 24 is a graph showing predicted lowpass characteristics of the family room home theater system of Example 3 with low frequency
optimization applied to four subwoofers in the system (subwoofers 1, 2, 3, and 4 shown in FIG.
21) It is. FIG. 25 is a layout example of the home theater system of the room without partitions in
Example 4. FIG. 26 is a graph showing the low frequency characteristics of the home theater
system of the room without partitions of Example 4 in which only the subwoofer 1 shown in FIG.
25 is activated without performing low frequency optimization. FIG. 27 shows the predicted low
of the undivided room home theater system of Example 4 with low frequency optimization
performed to determine that subwoofer positions 1, 2, 4 and 5 shown in FIG. 25 are optimal. It is
a graph which shows a zone characteristic. FIG. 28 is a layout example of the engineering
listening room of Example 5. FIG. 29 is a graph showing predicted low-frequency characteristics
of the engineering listening room of Example 5 in which only the subwoofer 1 shown in FIG. 28
is activated without performing low-frequency optimization. FIG. 30 is a graph showing predicted
low-pass characteristics of the engineering listening room of Example 5 in which low-frequency
optimization was performed on one active subwoofer. FIG. 31 is a graph showing the predicted
low-pass characteristics of the engineering listening room of Example 5 without low frequency
optimization and with the front two corners subwoofers (subwoofers 1 and 3 shown in FIG. 28)
active. is there. FIG. 32 is a graph showing predicted low-pass characteristics of the engineering
listening room of Example 5 where low-frequency optimization was performed on two active
subwoofers. FIG. 33 shows the predicted low range of the engineering listening room of Example
09-05-2019
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5 due to the configuration in which subwoofers are installed at the four corners (subwoofers 1, 3,
5 and 7 shown in FIG. 28) without low frequency optimization It is a graph which shows a
characteristic. FIG. 34 shows predicted low-pass characteristics of the engineering listening room
of Example 5 according to the configuration in which subwoofers are installed at four corners
(subwoofers 1, 3, 5 and 7 shown in FIG. 28) with low frequency optimization FIG. Figure 35
shows the predicted low for the engineering listening room of Example 5 without low frequency
optimization for the configuration with subwoofers installed at four midpoints (subwoofers 2, 4,
6 and 8 shown in Figure 28) It is a graph which shows a zone characteristic.
FIG. 36 shows predicted lows of the engineering listening room of Example 5 with low frequency
optimization for the configuration with subwoofers installed at four midpoints (subwoofers 2, 4,
6 and 8 shown in FIG. 28) It is a graph which shows a characteristic. FIG. 37. Engineering of
Example 5 where optimal 4-subwoofer configurations (subwoofers 2, 5, 6 and 7 shown in FIG.
28) were determined using spatial variation as a ranking factor and low frequency optimization
was performed. It is a graph which shows the prediction low-pass characteristic of a listening
room. FIG. 38 determines the optimal four subwoofer configuration (subwoofers 1, 5, 6, and 7
shown in FIG. 28) using spatial variation and spatial average variation as ranking factors, and low
frequency optimization FIG. 16 is a graph showing predicted low-pass characteristics of the
engineering listening room of Example 5 performed. FIG. FIG. 39 determines the optimal four
subwoofer configurations (subwoofers 1, 5, 6, and 7 shown in FIG. 28) using spatial variation and
acoustic efficiency as the ranking factors, and performs low frequency optimization. FIG. 16 is a
graph showing predicted low-frequency characteristics of the engineering listening room of
Example 5. FIG. FIG. 40 is a graph in which solutions are ranked on the basis of spatial variation
with respect to the low-pass characteristics of FIGS. FIG. 41 shows predicted low-pass
characteristics of the engineering listening room of Example 5 of the configuration (subwoofers
1, 3, 5 and 7 shown in FIG. 28) in which subwoofers are arranged at four corners with optimized
gain and delay. It is a graph. FIG. 42 shows measured low-pass characteristics of the engineering
listening room of Example 5 of the configuration (subwoofers 1, 3, 5 and 7 shown in FIG. 28) in
which subwoofers are arranged at four corners with optimized gain and delay It is a graph. FIG.
43 is a graph showing the predicted low frequency response in a typical sedan type automobile
when the speakers in the front door and on the rear deck are driven "uniformly". FIG. 44 is a
graph showing predicted low frequency response in a typical sedan car with speakers in the front
door and on the rear deck, optimized using sound field management. FIG. 45 is a graph showing
the predicted low frequency response in a typical sedan car when the speakers in all four doors
and on the rear deck are driven "uniformly". FIG. 46 is a graph showing the predicted low
frequency response in a typical sedan with speakers in all four doors and on the rear deck,
optimized using sound field management. FIG. 47 is a graph showing the predicted low
frequency response of a Sports Utility Vehicle (SUV) "Benchmark" setup.
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FIG. 48 is a graph showing the predicted low frequency response of an SUV after optimization
using sound field management. FIG. 49 is a graph showing the measured frequency response
with a single microphone at each seat of the SUV of FIG. FIG. 50 is a graph showing the measured
frequency response using a microphone array at each seat of the SUV of FIG. FIG. 51 is a block
diagram of a seven channel sound system configuration that may be enhanced or optimized. FIG.
52 is another block diagram of a seven channel sound system configuration that may be
enhanced or optimized.
[0068]
DETAILED DESCRIPTION OF THE INVENTION A system is provided for configuring an audio
system for a given space. To configure an audio system, the system may analyze candidate
configurations of the audio system statistically. Configuration candidates may include
loudspeaker position, number of loudspeakers, loudspeaker type, listening location, correction
factor, filter, or any combination thereof. By statistical analysis, configuration candidates include
the degree of agreement of the prediction transfer function, the flatness of the prediction transfer
function, the difference in the total sound pressure level between the seats to the prediction
transfer function, the efficiency of the prediction transfer function, or the output of the
prediction transfer function May indicate at least one metric of The system selects the position of
the loudspeakers in the audio system with single or multiple listening places, the number of
loudspeakers, the type of loudspeakers, the correction factor, the listening factor, the crossover
filter, or a combination of these schemes Also provide methods for
[0069]
FIG. 4 shows a room 400 defined by a room boundary wall 402, which can improve audio
performance such as low-pass characteristics by the method described herein. The room 400
may include any type of space in which the loudspeakers are arranged. This space may be
completely surrounded by a boundary, such as a room with a closed door or inside a vehicle
(such as a car or truck), or a room connected to the entrance, a room with an open door, a room
without a partition Alternatively, the vehicle may be partially surrounded by a boundary, such as
a vehicle with an open sunroof. Low-range characteristics within the space are described in the
present specification and the appended claims regarding the room, but include vehicle interiors,
recording studios, household living spaces, concert halls, cinemas, partially enclosed spaces etc.
It goes without saying that Room boundaries, such as room boundary wall 402, include partitions
that partially or fully surround the room. Room boundaries may be made of any material, such as
plaster, wood, concrete, glass, leather, textiles, and plastics. In homes, room boundaries are often
09-05-2019
23
made of plaster, walls, or fabrics. Boundaries may include walls, drapes, furniture, fixtures, and
the like. In vehicles, the boundaries of rooms are often made of plastic, leather, vinyl, glass, etc.
Room boundaries differ in their ability to reflect, diffuse and absorb sound. The acoustic
properties of the room boundaries may also affect the acoustic signal.
[0070]
The room 400 includes a sound system 470, which may include a CD player, tuner, sound source
412 such as a DVD player, an optional processor 404, an amplifier 410, and a loudspeaker 414.
Dotted line 470 indicates that sound source 412, optional processor 404, amplifier 410 and
loudspeaker 414 may be included in the sound system.
[0071]
Loudspeaker 414 may include a loudspeaker housing generally having a box-like configuration
surrounding a transducer. The loudspeaker enclosure may have walls or other shapes and
configurations adapted to environmental conditions, such as in a vehicle, etc., at the loudspeaker
location. Also, the loudspeaker may utilize a wall or part of the vehicle as a whole or part of its
housing.
[0072]
The loudspeaker may provide a full range of acoustic frequencies from low to high. Many
loudspeakers have multiple transducers in a housing. The use of multiple transducers in the
loudspeaker enclosure generally allows the individual transducers to operate more effectively in
different frequency bands. The loudspeaker or a portion of the loudspeaker may be optimized to
provide a specific range of acoustic frequencies, such as low frequencies. Loudspeakers may
include dedicated amplifiers, gain controls, equalizers, and the like. The loudspeakers may have
other configurations, for example, with fewer or more components.
[0073]
A loudspeaker or part of a loudspeaker comprising a transducer optimized to generate low
09-05-2019
24
frequencies is generally referred to as a subwoofer. The subwoofer may include any transducer
capable of generating low frequencies. Unless stated otherwise, in the present specification and
the attached specification, loudspeakers capable of generating low frequencies are referred to by
the term subwoofer, provided that they generate low frequencies and respond to a common
electrical signal. Any possible loudspeakers or parts of loudspeakers are included in the
subwoofer.
[0074]
This room contains eight loudspeaker position candidates 440-447 and one or more
loudspeakers may be arranged. The number of loudspeaker position candidates may be smaller
or larger. The position or "position" of a loudspeaker is a physical location in space where a
loudspeaker such as a subwoofer may be placed. The location may include a corner of a room
inside the house, a wall, or a ceiling, or an interior panel of the vehicle.
[0075]
The room also includes six listening locations 450-455 where the listener can sit. Similarly, the
number of listening places may be smaller or larger. A listening location or "location" is a
physical area within the space where a listener can sit or stand. The location may include an
indoor lounge chair or chair, or a driver or pilot seat in a vehicle. The listening location may be
anywhere in the room, but is generally selected from an aesthetic and ergonomic point of view.
Also, the listening location may be selected based on the sound performance of the high
frequency band and the mid frequency band.
[0076]
By arranging the loudspeaker 414 at each of the loudspeaker position candidates 440 to 447
and measuring at each of the listening places 450 to 455, for each of the loudspeaker position
candidates 440 to 447, transmission is made at each of the listening places 450 to 455 You may
ask for a function. The transfer function measures frequencies in various ranges, such as less
than about 120 Hertz (Hz), less than about 100 Hz, less than about 80 Hz, less than about 60 Hz,
less than about 50 Hz, less than about 40 Hz, or between 20 Hz and 80 Hz. It is also good. For
example, a transfer function, such as a frequency response for the first candidate loudspeaker
position 440 may be determined at the first listening location 450. Thereafter, for each of the
09-05-2019
25
remaining loudspeaker position candidates 441 to 447, the work of obtaining the transfer
function at the first listening place 450 may be repeated. When considering a plurality of
listening places, the process of obtaining the transfer function at the second listening place 451
may be repeated for each of the loudspeaker position candidates 440 to 447, and this work may
be repeated until the final listening place 455 is reached. . In the configuration shown in FIG. 4,
eight transfer functions can be obtained for each of the listening places 450 to 455, so it is
possible to obtain a total of 48 transfer functions for the room 400.
[0077]
When using multiple types of loudspeakers, such as using Type A loudspeakers and Type B
loudspeakers, two transfer functions may be determined for each position candidate. The quality
of the type A loudspeaker and the type B loudspeaker may be different. By way of example only,
the type A loudspeaker may be a dipole loudspeaker and the type B loudspeaker may be a
conventional (single pole) loudspeaker. In the example where there are eight loudspeaker
position candidates for each of the position candidates, such as position 440, the 140A and 140B
transfer functions may be determined for each of listening places 450-455. For the sake of
simplicity, the subsequent use of the term position is limited to the use of one type of
loudspeaker, but more than one type of loudspeaker may be considered.
[0078]
Any acoustic appearance may be measured by the transfer function to be determined. For
example, the transfer function to be determined may include an amplitude or volume component
and a phase component. If the amplitude and phase values are required, the transfer function
may be determined by any method that can obtain them. The amplitude component and the
phase component of the transfer function may be represented as a vector. The transfer function
may be determined at one frequency or tone, or at multiple frequencies or tones, such as from 20
Hz to 20,000 Hz in 2 Hz steps. The considered frequency interval may also be referred to as
frequency resolution.
[0079]
The acoustic signal may exit the loudspeaker 414 and interact with the room boundary 402 to
reflect in the transfer function the deviations in amplitude and / or phase that occur in the
09-05-2019
26
acoustic signal as it reaches the listening locations 450-455. The transfer function may reflect
the deviation introduced by the irregular non-parallelogram room and the room not completely
enclosed. There is no need to measure room dimensions, acoustics of room boundaries 402, etc.
to determine the transfer function. Rather, the acoustic signal is output from the loudspeaker
414 located at one of the candidate locations 440-447 and recorded by a microphone or other
acoustic measurement device placed at one of the listening locations 450-455 You may
[0080]
In FIG. 5, a system for implementing the present invention may include a sound system 500, a
measuring device 520, and a computing device 570. The sound system may comprise a general
purpose sound system having a sound processor 502, external components 512, and
loudspeakers 1-N (514, 516 and 518 in the figure). The sound system may have other
configurations and may have more or fewer components.
[0081]
The sound processor 502 may include a receiver, a preamplifier, a surround sound processor,
and the like. Sound processor 502 may operate in the digital domain, the analog domain, or a
combination of both. Sound processor 502 may include processor 504 and memory 506.
Processor 504 may perform arithmetic operations, logical operations, and / or control operations
by accessing system memory 506. Sound processor 502 may further include an input / output
device (I / O) 508. As described below, input / output device 508 receives an input and sends an
output to measurement device 520 and external component 512.
[0082]
Sound processor 502 may further include an amplifier 510 coupled to processor 504. The
amplifier 510 may operate in the digital domain, the analog domain, or a combination of both.
Amplifier 510 may send control information (such as current) to one or more loudspeakers to
control the audio output of the loudspeakers. Examples of loudspeakers include loudspeakers 1
to N (514, 516, and 518 in the figure). Alternatively, loudspeakers 1-N (514, 516 and 518 in the
figure) may include amplifiers and / or other control circuitry. Loudspeakers 1 to N (514, 516
and 518 in the figure) may be loudspeakers of the same efficiency (sound output for a given
power input) and design. Alternatively, the loudspeakers 1-N (514, 516 and 518 in the figure)
09-05-2019
27
may differ in efficiency and design, respectively. Sound processor 502 may receive input from
external component 512 and send output to external component 512. Examples of external
components 512 include, but are not limited to, turntables, CD players, tuners, and DVD players.
Depending on the configuration, one or more digital to analog converters (DACs) (not shown)
may be implemented after the external components 512, the processor 504, or the amplifier
510.
[0083]
The measuring device 520 enables the measurement of the sound signal output from the sound
system 500, for example (l) one, several or the amplitude of the sound signal output at a range of
frequencies, and / or (2) The amplitude and phase of the acoustic signal output at one, several or
a range of frequencies can be measured. One example of a measurement device is a sound
pressure level meter, which may determine the amplitude of the acoustic signal. Another example
of a measurement device is a transfer function analyzer, which may determine the amplitude and
phase of the acoustic signal. As described below, the transfer function analyzer may plot the data
to generate an output file, which may be sent to the computing device 570 for processing.
[0084]
The measuring device 520 may comprise a general purpose calculator that includes the ability to
measure acoustic signals. For example, a transfer function analyzer PCI card 562 may be
included in the measurement device 520 to provide an audio measurement function.
Alternatively, the measuring device 520 may comprise a device having a dedicated function of
the transfer function analyzer.
[0085]
The measuring device 520 may include a processing device 532, a system memory 522, and a
system bus 538 that couples various system components including the system memory 522 to
the processing device 532. Processor 532 may perform arithmetic operations, logical operations,
and / or control operations by accessing system memory 522. System memory 522 may store
information and / or instructions used in combination with processing unit 532. The system
memory 522 may include volatile and non-volatile memory such as random access memory
(RAM) 524 and read only memory (ROM) 530. The ROM 530 may store a basic input / output
09-05-2019
28
system (BIOS). The BIOS may include basic routines that help to transfer information between
elements in the measurement device 520, such as at start up. System bus 538 may be any of a
variety of bus structures, including a memory bus or controller, a peripheral bus, and a local bus
using any of a variety of bus architectures.
[0086]
The measuring device 520 comprises a hard disk drive 542 for reading and writing to a hard
disk (not shown) and an external disk drive 546 for reading or writing to a removable external
disk 548. It may further include. The removable disk may be an optical disk such as a magnetic
disk for a magnetic disk drive or a CDROM for an optical disk drive. The output file generated by
the transfer function device described above may be stored on removable external disk 548 and
transferred to computing device 570 for further processing. The measuring device may have
other configurations, for example with fewer or more components.
[0087]
Hard disk drive 542 and external disk drive 546 may be connected to system bus 538 by hard
disk drive interface 540 and external disk drive interface 544, respectively. The drive and its
computer readable medium may provide nonvolatile storage of computer readable instructions,
data structures, program modules and other data for the measuring device 520. In the typical
environment shown in FIG. 4, a hard disk and an external disk 548 are used, but in this typical
operating environment, data such as a magnetic cassette, flash memory card, random access
memory, read only memory, etc. are used. Other types of computer readable media that can be
stored and have computer access to this data can also be used.
[0088]
A number of programs, including hard disk, external disk 548, ROM 530, or RAM 524, operating
system (not shown), one or more application programs 526, other program modules (not shown),
and program data 528. It may store modules. One such application program may include the
transfer function analyzer function downloadable from the transfer function PCI card 562.
[0089]
09-05-2019
29
A user may enter commands and / or information into the measurement device 520 via an input
device such as a keyboard 558. A microphone 560 may be used to measure audio output. Other
input devices (not shown) may include a mouse or other pointing device, a sensor other than the
microphone 560, a joystick, a game pad, a scanner or the like. These and other input devices may
be connected to the processing unit 532 via a serial port interface 554 coupled to the system bus
538 or may be parallel port interface 550, game port or universal serial bus (USB) etc. It may be
summarized by other interfaces. Additionally, printer 552 may be used to print information.
Printer 552 and other parallel input / output devices may be connected to processing unit 532
via parallel port interface 550. A monitor 537 or other type of display device is also connected to
system bus 538 via an interface, such as video input / output device 536. The measuring device
520 may include, in addition to the monitor 537, other peripheral output devices (not shown)
such as loudspeakers or other audible output devices.
[0090]
As described in more detail below, the measuring device 520 may communicate with other
electronic devices, such as the sound system 500, to measure acoustic signals in various areas of
the room. One of the loudspeakers 514, 516, and 518 may be located on one, some or all of the
loudspeaker position candidates 440-447. A microphone 560 or other type of acoustic signal
sensor may be placed on one, some or all of the listening location candidates 450-455. A
loudspeaker may be controlled by the sound system 500 to emit a predetermined acoustic signal.
The audio signal output from the loudspeaker may then be detected by the microphone 560 at
the listening location. Next, various aspects such as the amplitude and phase of the output
acoustic signal may be recorded by the measuring device 520.
[0091]
Control of the sound system 500 to emit a predetermined acoustic signal may be implemented in
various ways. To control the sound system 500, the measurement device 520 may provide
commands from the input / output device (I / O) 534 to the input / output device 508 via line
564. The sound system may then emit a predetermined acoustic signal based on commands from
the measurement device. The sound system may also send predetermined signals to the arranged
loudspeakers without receiving commands from the measuring device. For example, external
component 212 may include a CD player. A specific CD may be inserted into this CD player and
played back. During playback, the acoustic signal output from the loudspeaker may be detected
09-05-2019
30
by the microphone 560 at the listening location.
[0092]
The acoustic signals output from different loudspeaker locations for different listening locations
may be stored on an external disc 548 or the like. The external disk 548 may be an input to the
computing device 570. Computing device 570 may be another computing environment and may
include many or all of the elements described above with respect to measurement device 520.
The computing device 570 may include more sophisticated processing devices than the
processing device 532 to perform the following numerically intensive statistical analysis.
[0093]
As discussed further below, the correction may also be implemented at multiple locations within
the sound processor 502, processor 504, amplifier 510, loudspeakers 1-N (514, 516, and 518 in
the figure), or the sound system 500. Good. Sound processor 502 may implement a time delay
prior to digital to analog conversion. Sound processor 502 may implement gain correction and /
or equalization in the analog or digital domain. Settings for correction, such as 6 dB amplitude
reduction for loudspeaker 514 may be input by the user to sound processor 502. The
implementation of these settings may be automated by the sound system 500.
[0094]
As shown in FIG. 5, the measurement device 520 is separate from the sound system 500.
Alternatively, the functionality of the measuring device 520 may be incorporated into the sound
system 500. Furthermore, as shown in FIG. 5, the measuring device 520 is separate from the
computing device 570. If the measuring device 520 has sufficient computing power, it is not
necessary to use the calculating device 570, and the measuring device 520 may perform the
measurement and the following calculation. Sound system 500, measuring device 520, and
computing device 570 may have other configurations, for example, having fewer or more
components.
[0095]
09-05-2019
31
FIG. 6 is a flow chart 600 that schematically illustrates an approach for selecting a configuration
to improve performance such as low pass characteristics of a sound system. The configuration of
the sound system may include parameters or parameter sets for the sound system. The
parameters may include anything that affects the transfer function at the listening location, for
example (1) loudspeaker position, (2) number of loudspeakers, (3) loudspeaker type, (4)
correction Settings, (5) listening places, and / or (6) crossover filters etc. may be included.
[0096]
Parameter value candidates may be selected, as indicated at block 602, to analyze audio system
configuration candidates. For example, loudspeaker position candidates may be selected. The
position candidate may include any position in a predetermined space where the loudspeaker can
be arranged. For example, the position candidates may include a plurality of discrete position
candidates input by the user, such as eight loudspeaker position candidates 440-447 shown in
FIG. 4. In a space such as a vehicle, position candidates for loudspeakers may be determined in
advance. As another example, loudspeaker number candidates may be selected. The loudspeaker
number candidate may include any number as possible as the number of loudspeakers in the
predetermined space. This number may include an upper limit, a lower limit, or an upper or
lower limit. For example, the candidate for the number of loudspeakers may include the
minimum number and the maximum number of loudspeakers. As yet another example,
loudspeaker type candidates may be selected. The types of loudspeakers may include different
qualities of loudspeakers. For example, the types of loudspeakers may include bipolar
loudspeakers and unipolar loudspeakers. In yet another example, the space may include a
discrete number of listening location candidates. Generally, the listening location is
predetermined and can not be changed. However, a flexible spatial configuration may allow one
or more listening places to be selected from a plurality of listening place candidates.
[0097]
Further, correction setting value candidates may be selected. The correction settings may include
adjustments to improve low-pass characteristics when implemented in the sound system 500
without depending on the placement of the loudspeakers. This correction may be applied to one
or more loudspeakers. The correction may be combined with the optimal number and location of
loudspeakers, or each may be considered separately, to improve frequency performance
including low frequency characteristics. Examples of correction settings include corrections to
gain, delay, and filtering. Examples of filtering may include band cut or notch, band pass, low
09-05-2019
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pass, high pass, all pass (change of phase rather than amplitude), and FIR (finite impulse
response). The filtering correction setting may be referred to as an equalizer correction setting as
it may be used to equalize the frequency response to different listening locations. The selection
of sound system parameters will be described in more detail with respect to FIG.
[0098]
As indicated at block 604, transfer functions for candidate loudspeaker locations may be input at
a single or multiple listening locations. The measurements for the determined transfer function
may be performed at 2 Hz resolution using the MLSSA acoustic measurement system. A
flowchart of transfer function determination is described in more detail below with respect to
FIG.
[0099]
As indicated at block 606, the transfer function may be modified based on the sound system
parameter value candidates. Sound system parameter value candidates may be combined to
represent possible audio system configurations. For example, the sound system parameter value
candidate is any combination of parameter candidates, such as a combination candidate of
speakers, a correction coefficient candidate, a crossover filter candidate, a loudspeaker type
candidate, a listening location candidate, or a combination candidate of a speaker and a
correction coefficient candidate May be represented. Based on the system's configuration
candidates, previously recorded transfer functions may be combined and / or adjusted. Thus, the
modified transfer function may represent a transfer function predicted for a candidate sound
system configuration. The transfer function correction is described in more detail with respect to
FIG.
[0100]
Next, as indicated at block 608, one or more of analysis techniques, such as statistical analysis
techniques, may be applied to the prediction transfer function. Statistical analysis may be used to
evaluate various configurations of the audio system, including one or more parameter value
candidates. Specifically, statistical analysis improves the frequency performance of the sound
system, such as the improvement of low-pass characteristics, by considering the individual
effects of multiple sound system parameters or the combined effects of combining these
09-05-2019
33
parameters. Provide a rational approach to This statistical analysis may measure a single aspect
or metric, or multiple aspects or metrics, for the predicted transfer function. For example, this
statistical analysis may indicate a particular uniformity or modality of the prediction transfer
function, such as flatness, match, efficiency, etc. Specifically, when examining an audio system
having a single listening location, statistical analysis may analyze the efficiency or flatness of the
predicted transfer function for a single listening location. When examining an audio system
having multiple listening locations, statistical analysis may analyze the efficiency, flatness, or
variations between listening locations of the predicted transfer function at each listening
location. An example of statistical analysis is described with respect to FIGS.
[0101]
As indicated at block 610, parameter values may be selected based on statistical analysis.
Statistical analysis may be used to compare predicted transfer functions to each other as various
aspects of the predicted transfer functions may be measured. One way of comparison is the
ranking of configuration candidates based on values such as the determined amplitude or
variation. For example, after calculating average spatial variation, spatial average variation, and
acoustic efficiency for each solution candidate, the results may be ranked to select the best
configuration. Prioritize or weight these metrics, assuming that there is no highest ranked
configuration in all categories (eg, lowest average spatial variation, lowest variation of spatial
average, and highest acoustic efficiency factor) You may Next, parameters for better or best
configuration candidates may be selected as compared to other configuration candidates.
[0102]
Next, as shown in the description of block 612 and the detailed description of FIG. 14, values
corresponding to the selected solution may be implemented in the sound system. After
implementing the value of this solution, the global correction method to improve low-pass
characteristics is uniform to all loudspeakers in system 500, as shown in block 614, to further
improve low-pass characteristics. Or you may apply substantially uniformly. The transfer
function of the sound system may then be remeasured to confirm the performance improvement.
Additionally, values corresponding to the selected solution and global correction factors may be
implemented. For example, in the case of a vehicle, it may be selected at various times, such as
before installing the audio system in the vehicle, while installing the audio system in the vehicle,
or after installing the audio system in the vehicle (eg at the point of sale of the vehicle) The audio
system for the vehicle may be configured with values corresponding to the solution and / or the
global correction factor. The flowchart 600 may have fewer steps than in FIG. 6, or may add
09-05-2019
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steps not shown in FIG.
[0103]
Global equalization is a type of global correction method to improve low-pass performance.
Global equalization may be applied uniformly or nearly uniformly to all loudspeakers in the
sound system 500. Since statistical analysis can determine a solution that favors peaks rather
than dips in the amplitude response, global equalization may be applied to reduce the amplitude
of the resulting peaks. Thus, after the selection and implementation of the solution at block 610
and block 612, the low pass characteristics may be further enhanced. As indicated at block 614,
additional parametric equalization or other types of equalization may be utilized to implement
global equalization. The amplitude values previously corrected for all loudspeakers may be
corrected in a substantially uniform manner in order to determine global equalization parameters
optimized by statistical analysis.
[0104]
(Selection of Parameter Candidates) FIG. 7 is a block diagram expanding the block 602 of FIG. 6,
and shows a method of selecting parameter candidates of the audio system. The method may
include, as indicated at block 702, selecting one or more listening locations to improve frequency
performance. For example, if the listening places may be selected from a plurality of listening
place candidates (for example, two listening places are selected from five listening place
candidates), listening place candidates may be input. The method may further include, as
indicated at block 704, selecting candidate locations where loudspeakers may be located. This
choice may be based on aesthetic or other aspects. Furthermore, if multiple types of
loudspeakers are considered in this analysis, the types of loudspeakers may be selected. As
shown at block 706, frequency resolution may also be selected. The choice of frequency
resolution may be based on the desired resolution level and the computing power of computing
device 570. The user may further select the minimum and maximum number of loudspeakers to
place in the position candidate, as shown in blocks 708 and 710. For example, for four candidate
loudspeaker locations, a minimum of one loudspeaker and a maximum of three loudspeakers
may be considered.
[0105]
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35
Blocks 712, 714, and 716 indicate the selection of correction settings, ie, the selection of
"corrections" that may be considered for subsequent implementation at a particular loudspeaker
position. As noted above, the correction includes adjustments that may improve frequency
performance, such as low-pass characteristics, that do not depend on loudspeaker placement
when implemented in a sound system. The correction may be individually determined at the time
of statistical analysis of each loudspeaker position candidate and implemented separately for
each loudspeaker to be arranged.
[0106]
As indicated at block 712, the number and value of gain settings to be considered in each
loudspeaker position candidate may be selected. Unlike the equalization levels described below,
gain settings are commonly referred to as loudness or volume settings because they can affect all
frequencies reproduced by the loudspeaker, ie, they are not frequency dependent. Although the
number and value of gain settings to be considered in each loudspeaker position candidate may
be arbitrarily selected, three gain settings 0, -6, and -12 dB may be selected. These values are
expressed as dB reduction from 0 dB or 1 which is the baseline of the acoustic output, although
increases may also be used since the dB values are relative.
[0107]
As indicated at block 714, the number and value of delay settings to be considered at each
loudspeaker position candidate may be selected. By introducing a delay into the loudspeaker, the
phase of the acoustic signal to be reproduced may be changed. The number and value of delay
settings to be considered in each loudspeaker position candidate may be arbitrarily selected. For
example, three delay settings 0, 5, and 10 milliseconds may be selected.
[0108]
Filtering may be applied to one, some or all loudspeaker position candidates. One example of
filtering is equalization. As indicated at block 716, the number and value of equalization settings
to apply to each loudspeaker position candidate may be selected. Equalization may include
various types of analog or digital equalization, including parametric, graphic, parametric,
shelving, finite impulse response (FIR), and transversal equalization. Equalization settings include
frequency settings (eg, center frequency), bandwidth settings (eg, bandwidth surrounding the
09-05-2019
36
center frequency for applying the equalization filter), level settings (eg, the amount by which the
amplitude reduces or increases the signal) And the like may be included. Thus, for one
loudspeaker position candidate, such as a first equalization setting at a first center frequency and
a second equalization setting at a second center frequency, or various types of equalization, etc.
Multiple equalization settings may be applied. In addition, equalization may be applied to all
frequencies of interest. For example, in low frequency analysis targeted at 20-80 Hz, equalization
may be applied to all relevant frequencies. To reduce processing time, the frequency with the
largest variation may be selected, as further described with respect to block 1106 of FIG. When
limiting the frequency selection in this way, three bandwidth parameters and three level
parameters may be selected. For convenience, the bandwidth may be referred to as a filter Q (Q).
Q may be defined as the center frequency Hertz value divided by the frequency range Hertz value
to which the level adjustment applies. For example, if a center frequency of 50 Hz is selected,
then the bandwidth for Q = 2 will be 25 Hz. Suitable Q parameters include, but are not limited to:
1, 4 and 16. Suitable level parameters include, but are not limited to, 0, -6, and -12 dB.
[0109]
As shown in block 718, based on the selections made at 702-716, the number of transfer
functions to be considered during statistical analysis may be determined. These transfer
functions may include transfer functions modified by one or more correction settings, transfer
functions for a single loudspeaker location, and transfer functions combined to represent
multiple loudspeaker locations. It may not be possible to investigate all possible combination
candidates such as loudspeaker position, number of loudspeakers, gain settings, delay settings
and equalization settings. If this is not possible, a subset of candidate solutions may be examined.
As this subset, a subset with sufficient resolution, that is, a subset that is not too coarse to miss
the best solution and too fine to take too long to investigate may be selected. The change in the
investigation step size of the parameter greatly affects the calculation time. The change of the
survey parameter may be estimated using the following equation (4).
[0110]
Here, T is an estimated value of the calculation time.
[0111]
Tref is the time required to investigate one unique combination of loudspeaker position,
loudspeaker number, gain setting, delay setting, equalization setting, etc.
09-05-2019
37
[0112]
N is the number of loudspeaker position candidates.
[0113]
K is the number of loudspeakers actually used.
[0114]
A is the number of loudspeaker amplitude levels to investigate.
[0115]
T is the number of signal delay values to investigate.
[0116]
FL is the number of filter cut levels to investigate.
[0117]
FQ is the number of filter Q values to investigate.
[0118]
S is the number of listening places to be optimized.
[0119]
Is the number of selection methods which can select the loudspeaker position candidate number
N to K at one time in the following case.
[0120]
perm (K) is a permutation number of K loudspeakers, and perm (K) = K!
である。
09-05-2019
38
[0121]
In block 606, any number of transfer functions may be considered during statistical analysis, but
to reduce calculation time, as shown in block 722, for example, the selected frequency resolution,
the number of loudspeakers to select, The number of corrections selected and / or the correction
settings may be reduced.
As indicated at block 720, once the acceptable number of transfer functions have been
determined for statistical analysis, these transfer functions may be input.
The number of steps in block 602 may be less than in FIG. 7 or may be added to steps not shown
in FIG.
[0122]
Transfer Function Recording FIG. 8 is an expanded block diagram of block 604 of FIG. 6 showing
the input of the transfer function corresponding to a particular loudspeaker position for each
listening location.
As indicated at block 802, the loudspeaker may be located at a first candidate position, such as
position 440 of FIG.
Next, as indicated at block 804, a microphone (or other acoustic sensor) may be placed at a first
listening location, such as location 450 of FIG.
Next, as indicated at block 806, the transfer function for the first candidate loudspeaker location
is recorded at the first listening location using the measuring device 520, corresponding to the
acoustic signal generated by the sound system 500. It is also good.
This procedure is described in more detail with respect to FIGS. 4 and 5.
09-05-2019
39
[0123]
If there are more listening locations (including candidate listening locations) as shown in block
808, then the microphone may be moved to the next listening location as shown in block 810.
For example, the microphone may be moved to location 451 of FIG.
The measurement may then be repeated as indicated at block 806.
If there are more loudspeaker position candidates as indicated at block 812, then the
loudspeaker may be moved to the next position candidate as indicated at block 814. For example,
the loudspeaker may be moved to position 441 in FIG. The measurement may then be repeated
as indicated at block 806. This procedure may be repeated until transfer functions for all
candidate loudspeaker locations are recorded at each listening location. Block 604 may be less
than the number of steps of FIG. 8 or may add steps not shown in FIG.
[0124]
(Modification of Transfer Function) In order to determine a predictive transfer function, the
recorded transfer function may be modified based on the candidate configuration of the audio
system. Configuration candidates may include any one parameter value candidate, any
combination of parameter value candidates, or any partial combination in the audio system, and
their various permutations. For example, candidate configurations may be different loudspeaker
positions, different loudspeaker types, different correction factors, different crossover filters, or
any combination of loudspeaker positions, loudspeaker types, correction factors, or crossover
filters or Partial combinations may be included. Transfer function modifications may include
combinations of transfer functions, and / or adjustments of transfer functions. The modified
transfer function may represent a predicted transfer function at a single listening location for
parameter value candidates (i.e., loudspeaker position candidates, loudspeaker type candidates,
correction setting candidates, crossover filter candidates, etc.).
[0125]
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40
As an example of the transfer function combination, the configuration candidate may include the
arrangement of loudspeakers at the locations 440 and 442 and the listening location 451. Two
transfer functions in memory (the first transfer function recorded at location 451 when the
loudspeaker is at location 440 and the location when the loudspeaker is at location 442 to
predict a two loudspeaker configuration) The second transfer function (recorded at 451) may be
accessed and combined. As described below, the transfer functions may be combined by
superposition. The transfer functions thus combined represent the acoustic signals generated by
the multiple loudspeakers at locations 440 and 442 at a listening location. As another example of
transfer functions, one may access the transfer functions for a particular type of loudspeaker. If
one of the candidate loudspeaker solutions includes the arrangement of loudspeakers of type A
at location 440 and the arrangement of loudspeakers of type B at location 442 and the listening
location is 451, then 2 in memory. Transfer functions (the first transfer function recorded at
location 451 when the loudspeaker of type A is at location 440, and the second transfer function
recorded at location 451 when the loudspeaker of type B is at location 442 The configuration
may be predicted by accessing and combining the transfer functions).
[0126]
Furthermore, as an example of adjustment of the transfer function, correction of the transfer
function based on the correction setting may be mentioned. After selection of the desired transfer
function, one or more of the selected transfer functions may be modified by one or more of the
correction setting candidates, such as gain settings, delay settings, or equalization settings. The
corrected transfer function may represent a predicted transfer function for the correction setting
candidate.
[0127]
FIG. 9 is an expanded block diagram of block 606 of FIG. 6 showing modification of the transfer
function. As indicated at block 902, a program or user executing on computing device 570 may
select a particular listening location. For example, in the case of a room environment that
includes two listening locations (eg, 451 and 452 in FIG. 4), either listening location may be
selected. Next, as shown at block 904, a program or user executing on computing device 570
may select a single loudspeaker position candidate, or a combination of loudspeaker position
candidates. For example, in a room environment that includes two loudspeaker position
candidates (eg, 440 and 442 in FIG. 4), a single loudspeaker position, or any combination of
loudspeaker positions (eg, 440 or 442, or 440) And 442). Next, as indicated at block 906, the
09-05-2019
41
program or user executing on the computing device 570 may select a transfer function for the
selected listening location that corresponds to the selected loudspeaker position or combination
of loudspeaker positions. . For example, if the listening location is 451 and the loudspeaker
position candidates are 440 and 442, then the transfer function at location 451 when the
loudspeaker is at location 440 and the location 451 when the loudspeaker is at location 442 And
the transfer function at.
[0128]
If these transfer functions include phase components, then the program executed by computing
device 570 selects the phase components of the transfer functions that are measured and stored
in memory, as shown in block 908. It may be corrected by any delay setting. For example, if one
of the optional delay settings includes a differential delay of 10 ms between the two
loudspeakers, one of the transfer function's phase components should be reflected to reflect the
introduction of the 10 ms time delay factor. It may be corrected. In the above example, if the
loudspeaker position candidates are 440 and 442, then the transfer function at location 451 for
the loudspeaker at location 440 is 10 ms with respect to the transfer function at location 451 for
the loudspeaker at location 442 May be delayed. For example, the transfer function at location
451 for the loudspeaker at location 440 may be delayed by 10 milliseconds. Alternatively, the
transfer function at location 451 for the loudspeaker at location 442 may be advanced by 10
milliseconds. Alternatively, the relative delay between the transfer functions may be 10
milliseconds by combining the corrections of both transfer functions. Thus, the transfer function
recorded at each loudspeaker position may be modified by applying one or more delay settings.
[0129]
The program executed by computing device 570 may modify the amplitude component of the
transfer function that is measured and stored in memory, as indicated at block 910, by any gain
setting selected at block 712. Thus, the numerical amplitude component can be increased or
decreased by a fixed amount such as 6 dB. Specifically, one, some or all of the transfer function
amplitudes may be modified. In the above example, the amplitude of the transfer function at
location 451 for the loudspeaker at location 442 may be increased or decreased relative to the
amplitude of the transfer function at location 451 for the loudspeaker at location 440. For
example, the transfer function at location 451 for the loudspeaker at location 442 may be
reduced by 6 dB. Alternatively, the transfer function at location 451 for the loudspeaker at
location 440 may be increased by 6 dB. Alternatively, the relative amplitude difference between
these transfer functions may be 6 dB by combining the corrections of both transfer functions.
09-05-2019
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Thus, one of a plurality of gain settings may be applied to each subwoofer to correct the transfer
function recorded at each listening location.
[0130]
Although not shown in FIG. 9, prior to the combination at block 912, the program executed by
computing device 570 shown in FIG. 5 may store stored transfer functions, such as equalization
settings selected at block 716. It may be corrected by any equalization setting. As noted above,
the transfer function may be modified by equalization settings including center frequency,
bandwidth and amplitude adjustment. The choice of center frequency, bandwidth and amplitude
adjustment may be limited to avoid computational complexity. Specifically, if equalization
correction is to be performed prior to the combination in block 912, calculating and applying
equalization filters at all frequencies where boost / cut levels and Q values may be multiple, the
calculation time It will be extremely long. Modification of the equalization settings may be
performed at block 1108 after determining the frequency at which spatial variation is greatest,
as described in more detail below with respect to FIG. For example, spatial variation may be
reduced by applying an equalization filter at a center frequency equal to the frequency of the
solution with the largest variation. This results in a significant reduction in computation time as
only one frequency is calculated for each filter / loudspeaker. Alternatively, the equalization
settings may be implemented prior to the determination of the maximum variation.
[0131]
The program executed on computing device 570 may combine the recorded or modified transfer
functions (eg, modified by correction factors such as delay, gain, and / or equalization) as shown
in block 912 A combination of amplitude response at the listening location may be provided for
the selected combination of loudspeaker positions. For example, the transfer function at location
451 for the loudspeaker at position 440 is not modified (no correction factor applied), and delay
and amplitude changes introduced by modifying the transfer function at location 451 for the
loudspeaker at position 440 You may At least a portion of these transfer functions may be
combined to determine a combined response. For example, the amplitude components of these
transfer functions may be combined. For example, the amplitude and phase components of these
transfer functions may be combined.
[0132]
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43
One way to combine these transfer functions may include superposition. If the loudspeakers,
rooms and signal processing involve linear systems, the principle of superposition may be
applied. Superposition involves linear addition of transfer function vectors. The vectors may be
added or summed for individual frequencies of the transfer function. For example, if the transfer
function vectors are measured at listening locations 451 for loudspeaker positions 440, 441 and
442, the amplitude response combining the three loudspeaker positions at each frequency is
obtained by adding the vectors for each frequency. You may give it. Also, transfer functions or
transfer function values modified by at least one of correction settings such as gain, equalization,
or delay settings may be combined.
[0133]
If any combinations of loudspeaker positions for the listening location selected in block 902
remain to be examined, then blocks 904-912 may be repeated as shown in block 914. If
additional delay settings are selected at block 714, then blocks 908-914 may be repeated, as
shown at block 916. If additional gain settings are selected at block 712, then blocks 910
through 916 may be repeated, as shown at block 918, and if additional listening locations are
selected at block 702, as shown at block 920: Blocks 902-918 may be repeated. Once all
listening locations, loudspeaker position candidates, delay setting candidates, and gain setting
candidates have been considered, the corrected and / or combined transfer function, ie, the
transfer function that can represent the predictive transfer function, is provided to each listening
location 922 Record against. The steps included in block 606 may be less than in FIG. 9 or may
add steps not shown in FIG.
[0134]
Statistical Analysis Various statistical analyzes may be performed to analyze the prediction
transfer function. FIG. 10 is a table showing raw data of different listening places (seats 1 to 5)
for different frequencies (20 to 80 Hz in 2 Hz steps) and an example of statistical analysis that
can be performed. As noted above, raw data may be modified based on one or more candidate
parameter values. For example, if the candidate values for correction include a center frequency
of 30 Hz, a bandwidth of 10 Hz, and a level setting of -6 dB, generate a prediction transfer
function by adjusting the raw data of frequencies 26 to 34 accordingly It is also good.
[0135]
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44
In the case of an audio system having multiple listening locations, the statistical analysis may be,
for example, an average between seats, standard deviation, spatial standard deviation, spatial
envelope, or spatial maximum average, and any numerical value for evaluating the prediction
transfer function It may be based on calculation tools. For example, the spatial average at 20 Hz
is -15.94 dB, which is calculated by averaging the amplitude readings for seats 1-5 at 20 Hz. The
spatial variation at 20 Hz is -4.72 dB, which is calculated taking the variation of the amplitude
reading for seats 1 to 5 at 20 Hz. The spatial standard deviation is 2.17 dB for 20 Hz, which may
be calculated as the square root of the spatial variation. The spatial envelope may be the
difference between the maximum and minimum readings. The spatial envelope is 5.14 dB
because the maximum reading at 20 Hz is -12.99 dB and the minimum is -18.13 dB. The spatial
maximum minus mean may be calculated by selecting the maximum value and subtracting the
mean value. Since the maximum at 20 Hz is -12.99 dB and the average is 15.94 dB, the spatial
maximum-average is 2.96.
[0136]
The average overall level may be calculated based on the spatial average. Other calculations may
be based on spatial average variance, spatial average standard deviation, spatial average
envelope, and spatial average such as spatial average maximum-average. For example, in FIG. 10,
the maximum-average of the spatial average is 6.42-(-8.97, average total level), or 15.39. As
shown in FIG. 10, mean spatial variation, mean spatial standard deviation, mean spatial envelope,
and mean spatial maximum-average are similarly calculated based on spatial variation, spatial
standard deviation, spatial envelope, and spatial maximum-mean. You may An example equation
for mean spatial variation is shown below.
[0137]
Here, vars (R (s, f)) is the magnitude (in dB) of the variation of the transfer function between all
the listening places calculated at any one frequency f.
[0138]
The statistical analysis may be based on an average of frequencies per seat, such as an average
level.
09-05-2019
45
For example, the average level -10.16 dB may be calculated by averaging all the frequencies in
the seat 1. As shown in FIG. 10, the average level at each seat may be used to calculate the
average overall level, the variation of the average level, the standard deviation of the average
level, the envelope of the average level, and the maximum-average of the average level .
[0139]
The variation of the spatial average may be defined as:
[0140]
Here, var (Rf (k)) is the magnitude (in dB) of the variation of the transfer function over all
frequencies calculated at any one listening location.
[0141]
S is the total number of listening places.
[0142]
The acoustic efficiency may be quantified by converting the total efficiency into the total power
versus the number of active loudspeakers.
Sound efficiency may be defined as follows.
[0143]
Here, a is the amplitude of the loudspeaker k in any given configuration.
[0144]
Statistical analysis may measure various metrics or aspects of the predictive transfer function.
The first type of statistical analysis may indicate the degree of agreement of the prediction
09-05-2019
46
transfer function across multiple listening locations.
When equalizing the system, examples of the first type above include average spatial variation,
average spatial standard deviation, average spatial envelope (ie, minimum and maximum), and
average spatial maximum.
For example, a low average spatial variation value indicates that the transfer function tends to
match at each seat (ie, values at all seats are close to the spatial average).
[0145]
A second type of statistical analysis may measure the need for equalization to the prediction
transfer function. In particular, the second type of statistical analysis may be a measure of
flatness. Examples of the second type include variation of spatial average, standard deviation of
spatial average, envelope of spatial average, and variation of spatial minimum. This analysis of
the variation of the spatial average provides a measure of the average agreement between the
seats.
[0146]
A third type of statistical analysis may measure the difference in total sound pressure level (SPL)
between the seats relative to the predictive transfer function. Examples of the third type include
mean level variation, mean level standard deviation, mean level envelope, and mean level
maximum mean.
[0147]
A fourth type of statistical analysis may examine the efficiency of the predicted transfer function
at a single listening location or multiple listening locations. In fact, this statistical analysis may be
a measure of the efficiency of the sound system for a particular frequency, group of frequencies,
or frequency range at a single listening location or multiple listening locations. An example of the
fourth type is acoustic efficiency. The acoustic efficiency may measure the average total level
divided by the total drive level for each loudspeaker. The acoustic efficiency to the predictive
09-05-2019
47
transfer function may be examined and the parameter or parameter group with the higher or
highest acoustic efficiency may be selected for the predictive transfer function.
[0148]
A fifth type of statistical analysis may examine the output of the predictive transfer function at a
single listening location or multiple listening locations. This statistical analysis may be a measure
of the sound system's raw output for a particular frequency, frequency group, or frequency
range. In the case of a system with a single listening location, average levels are an example of
statistical analysis to examine the output. In the case of a system with multiple listening
locations, an example average statistical level may be mentioned as an example of a statistical
analysis examining the output. The average overall level may indicate how loud the audio system
can play at a particular listening location or locations. A sixth type of statistical analysis examines
the flatness of the predicted transfer function at a single listening location. This statistical
analysis may analyze variations in the predicted transfer function, such as amplitude variations
and amplitude standard deviations at a single listening location.
[0149]
Band limiting may be performed in any of the above statistical analysis. For example, to
determine the amount of power at a particular frequency or set of frequencies, one may measure
the average total level in a particular frequency band, such as a frequency below 40 Hz.
Generally, the maximum power of the subwoofer is limited to less than 40 Hz for frequencies
above 40 Hz. Therefore, it may be convenient to optimize the average overall level to less than
40 Hz. Next, parameter candidates with the highest or higher average total power at these
listening locations in the 20-40 Hz range may be used for the audio system. Similarly, for audio
systems having a single location, it may be advantageous to optimize the average level to less
than 40 Hz. Various statistical analyzes may be performed as described above. FIG. 11 is an
example of an expanded block diagram of block 608 of FIG. 6 showing statistical analysis
examining acoustic efficiency and average spatial variation. This comparison may be performed
by a program executed by the computing device 570 shown in FIG. As shown in block 1102, a
spatial average may be derived by comparing transfer functions as a function of frequency
between listening locations. For example, predictive transfer functions may be compared as a
function of frequency.
[0150]
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48
The spatial average may include the average amplitude of the location, and may be output from a
single loudspeaker location or combination of loudspeaker locations, and a numerical
representation of the acoustic output sensed at multiple listening locations, such as 450-455 in
FIG. You may look as To determine the spatial average, the corrected or uncorrected amplitude
component of the transfer function output from a single loudspeaker position may be compared
between locations as a function of frequency, or multiple loudspeaker positions After or before
the correction of the combination of the transfer functions output from. This comparison may be
made in any way, but one way is to give a spatial average for each frequency by averaging the dB
values of the amplitude components from all the listening places as shown in FIG. How much the
amplitude component for each listening place changes from the spatial average may be
expressed as a change such as a place change. Thus, when the amplitude values 4 dB and 2 dB
are compared by averaging to give a spatial average of amplitude 3 dB, the spatial variation value
may be 2.
[0151]
As shown in FIG. 10, variability between amplitude values may be represented by sample
variability, standard deviation (STD), spatial envelope, spatial max-mean, or any other method of
representing variability between numerical values. It is also good. For example, if the 60 Hz
transfer function for the loudspeaker at position 440 is +1 dB at position 450, +1 dB at position
451, -2 dB at position 452, +2 dB at position 453, +3 dB at position 454, and +3 dB at position
455 The average amplitude is +1.33 dB and the spatial variation is 3.47.
[0152]
As shown in block 1104, spatial averages and spatial variations may be recorded. The program
executed by computing device 570 may determine the frequency at which spatial variation is
greatest among all listening locations for each loudspeaker position candidate and each
combination of loudspeaker position candidates, as shown in block 1106. This frequency may be
determined as the center frequency when applying equalization. Furthermore, when
implementing multiple equalizations, multiple center frequencies may be determined, such as the
three center frequencies at which spatial variations are greatest.
[0153]
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Next, as indicated at block 1108, the program executed at computing device 570 may modify the
determined center frequency amplitude with the equalization bandwidth and level settings
selected at block 716. Thus, for a selected bandwidth of the determined (or if the equalization
correction was performed prior to the combination in block 912), the numerical amplitude
component for the particular frequency is It may be increased or decreased. For example, an
amplitude reduction of 12 dB can also be applied with Q = 4 at 60 Hz. Unlike frequency
independent gain settings, numerical amplitude components at different frequencies may be
modified by different equalization level settings. Thus, one of the plurality of equalization settings
may be applied to the spatial average for one or a combination of loudspeaker position
candidates.
[0154]
As shown at block 1110, the modified spatial average may be recorded. If an additional
equalization setting is selected at 716, then blocks 1108-1110 may be repeated, as shown in
block 1112. If the spatial average has been modified with all selected equalization settings, the
modified or pre-modified spatial average may be compared, as shown in block 1114. This
comparison may be performed by a program executed by the computing device 570.
[0155]
As shown in block 1114, by comparing all spatial averages, a solution including acoustic
efficiency and average spatial variation for each combination of each loudspeaker position
candidate and loudspeaker position candidate for all listening locations The selected correction
may be added. FIG. 10 shows an example of the average overall level that can be used to
determine the acoustic efficiency and the average spatial variation.
[0156]
As noted above, the determined acoustic efficiency numerically indicates the ability of a given
sound system to produce higher sound levels at the one or more listening locations from the
same power input when the solution is implemented. . Thus, acoustic efficiency is the ratio of
sound pressure levels at one or more listening locations to the total low frequency electrical
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input of the sound system. For example, acoustic efficiency may include the average total level
divided by the total drive for all active loudspeakers. The determined spatial variation
numerically indicates the similarity of the low frequency acoustic signals detected at each
listening location when the solution is implemented.
[0157]
FIG. 12 is another example of a block diagram developed from block 608 of FIG. 6 showing
statistical analysis to determine acoustic efficiency and variation of spatial average. As indicated
at block 1202, the average level at each listening location may be determined by comparing the
amplitude response as a function of listening location over all the frequencies of interest. FIG. 10
shows a calculation example of an average level in which an average total level is calculated by
averaging the amplitudes of frequency groups at one listening location. Specifically, the average
level for seat 1 shown in FIG. 1 may be calculated by averaging the amplitudes of frequencies 2080. As shown in FIG. 10, the average overall level may be calculated by averaging these average
levels. Furthermore, as shown in FIG. 10, by analyzing these mean levels, the mean level
variation, the standard deviation of the mean level, the envelope of the mean level, and the
maximum-mean of the mean level may be determined. In addition to the mean level, amplitude
variations or amplitude standard deviations may be calculated. Amplitude variations may include
amplitude variations for a particular listening location. As in the example shown in FIG. 10, the
amplitude fluctuation is the fluctuation of the amplitude value relative to the seat 1 (-1777, 5.65) may be included. Amplitude variation may be a measure of the smoothness of the transfer
function (predicted transfer function or transfer function before correction) for a particular
listening location. In an audio system having multiple listening locations, the average amplitude
variation may be determined by averaging the amplitude variations for each listening location. In
audio systems having a single listening location, amplitude variation or amplitude standard
deviation may be used to statistically estimate the prediction configuration.
[0158]
The average overall level may be determined by averaging all recorded average levels, as shown
in block 1204. As indicated at block 1206, the average overall level may be used to calculate
acoustic efficiency. The acoustic efficiency may be determined by dividing the average overall
level by the total drive level for each loudspeaker. Acoustic efficiency numerically indicates the
ability of a given sound system to increase the sound level at one or more listening locations, or
low frequency sound levels for band limited analysis, from the same power input. As shown in
block 1208, the spatial average variance may be calculated by first calculating the spatial
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average at each listening location and then calculating the variance of these spatial averages. The
determined variation of spatial average numerically indicates how the amplitude value matches
the target value when the solution is implemented. As shown in block 1210, this variation in
acoustic efficiency and / or spatial average may be used to compare predicted transfer functions.
[0159]
FIG. 13 is a table of audio system configuration candidates, where the configuration candidates
are ranked based on mean spatial variation (MSV). These configuration candidates include values
corresponding to various combinations of audio system parameters of correction settings
including loudspeaker position, number of loudspeakers, and gain, delay, and equalization. The
first four configurations and another configuration (such as solution 10,000) are shown. Further,
FIG. 14 shows the value of acoustic efficiency (AE) and the value of variation of spatial average
(VSA) for the purpose of illustration. Other types of statistical analysis may be used.
[0160]
For each configuration candidate in FIG. 13, six listening locations, a minimum of two
loudspeakers, a maximum of three loudspeakers, and four loudspeaker position candidates are
considered. As the three gain setting candidate values, 0 dB, -6 dB, and -12 dB are considered. 0
ms, 5 ms and 10 ms are considered as delay settings. The center frequency for implementing
parametric equalization may include the frequency with the largest variation, as determined at
block 1106 of FIG. Bandwidth settings of 1, 4 and 16 are considered. 0 dB, -6 dB, and -12 dB are
considered as equalization level settings.
[0161]
This approach may recommend at least one candidate configuration based on statistical analysis.
This recommendation may be based on one or more statistical analyses. As shown in FIG. 13,
configuration candidates are ranked based on mean spatial variation (MSV). Alternatively,
solutions may be ranked based on acoustic efficiency (AE) and / or variation of spatial average
(VSA). Alternatively, these solutions may be ranked based on multiple statistical analyses, such as
ranking based on weighting of various statistical analyses. For example, various weights may be
assigned to average spatial variations, acoustic efficiency, and / or spatial average variations.
09-05-2019
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[0162]
The program executed by the computing device 570 or the user may manually select the solution
of the parameter according to the statistical analysis from the solution for explanation shown in
FIG. Solution 1 shown in FIG. 13 has low average spatial variations, so when the correction
settings shown for each system parameter are implemented on the candidate position 1 and 2
loudspeakers, the low frequency signals heard by each listener The similarity of is the largest. In
the case of solution 5, the acoustic efficiency is maximized, but the average spatial variation is
higher than the other solutions. In this way, the user may wish to implement Solution 2 with both
average spatial variation and acoustic efficiency well balanced, although the average spatial
variation is neither minimal nor acoustic efficiency maximum. Solution 3 has a minimum
variation in spatial average at each listening location, but has a larger average spatial variation
and lower acoustic efficiency than solution 2. Thus, also when considering the variation of the
spatial average, the solution 2 in which the combination of the spatial variation, the acoustic
efficiency, and the variation of the spatial average is good may be a desired option.
[0163]
Depending on the room and sound system, a particular solution may simultaneously improve the
acoustic efficiency, the average spatial variation and the variation of the spatial average, but may
also require a trade-off. The user may review the ranking results and implement the values
corresponding to the selected solution, in order to prepare the desired combination to improve
the low frequency. For example, the user may decide to reduce spatial variation at the expense of
some acoustic efficiency or vice versa.
[0164]
In addition to the user, a program running on computing device 570 may select a solution to
implement in the sound system by weighting the solution from the statistical analysis.
Specifically, if the solution that minimizes the average spatial variation greatly reduces the
acoustic efficiency, the program may select a desired solution based on the weighting factor
selected by the user. For example, suppose that the degree to which the user needs to improve
the acoustic efficiency is twice the reduction of the average spatial variation. Thus, in the case of
a trade-off between low-pass characteristics, the program executed by the computing device 570
may select a solution based on the weighting given by the user. As mentioned above, other types
09-05-2019
53
of statistical analysis may be used to evaluate candidate configurations. For example, amplitude
variations or mean amplitude variations may be used to evaluate candidate configurations.
[0165]
Column S in FIG. 13 indicates the number of loudspeakers and the position of each loudspeaker
by four position candidates. Each solution provides a value corresponding to a candidate position
at which to place the loudspeaker to implement the solution. Similarly, the number of
loudspeakers needed to implement the solution is also provided. For example, in the case of
solution 1, two loudspeakers are arranged at position candidates 1 and 2. For solution 5, three
loudspeakers are placed at positions 1, 3 and 4.
[0166]
Thus, each solution may show the effect of reducing or increasing the number of loudspeakers
used. Specifically, each solution may reveal whether it is effective to increase the number of
loudspeakers used (for example, whether the number of loudspeakers selected is three or two) It
does not affect the noise performance, ie does not degrade the performance of the low frequency
sound at the chosen listening location). Each solution allows the user to weight the cost of
additional loudspeakers and corrections to improve low-pass performance. For example, adding
parametric equalization to one of a pair of loudspeakers may improve spatial variation more than
adding two loudspeakers.
[0167]
The “Gain” column in FIG. 13 shows the gain settings implemented for each loudspeaker to
provide the desired improvement in low pass characteristics. As described above, statistical
analysis may independently determine the gain settings implemented for each loudspeaker
position candidate. For example, in solution 3, a 6 dB gain reduction is implemented for the
loudspeaker of candidate position 2 but no gain correction is implemented for the loudspeakers
located at candidate candidate 3.
[0168]
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54
Generally accepted acoustic theory predicts that the low pass performance will be improved by
equalizing the gain settings of the two loudspeakers that are at equal positions from the facing
vertical room boundaries and canceling the room mode. If the arrangement of the loudspeakers
is correct, the space is symmetrical and the acoustic properties of the spatial boundaries are the
same, this prediction may be true, but the acoustic properties of the spatial boundaries are
generally very different. Thus, if the loudspeaker locations are not equidistant from the room
boundaries, then statistical analysis may determine solutions with gain settings that improve lowpass performance. Further, even when the acoustic characteristics of the space boundary are not
uniform and not perpendicular to each other, and there is an opening such as a door, a solution
having a gain setting value that improves the low frequency characteristic may be determined.
[0169]
To increase the low frequency sound level heard at one or more listening locations, a solution
that lowers the gain setting at the candidate loudspeaker locations may be determined by
statistical analysis. This can be seen by comparing solution 1 and solution 3, when the unit gain
of both loudspeakers is 0, the acoustic efficiency of solution 3 brought about by the 6 dB gain
reduction for loudspeaker 2 is obtained from solution 1 It shows that it is higher than the
acoustic efficiency. This is intuitively contrary to the generally accepted acoustic theory that
lowering the volume reduces the sound level.
[0170]
The “delay” column in FIG. 13 shows the delay settings implemented at each loudspeaker
position of each solution. As described above, statistical analysis may independently determine
the delay settings to be implemented for each loudspeaker position candidate. Thus, in the case
of solution 3, a delay of 10 ms is implemented for the loudspeaker of position candidate 2 and no
delay is implemented for the loudspeakers placed at position candidate 3. Delay settings can also
have a positive impact on acoustic efficiency.
[0171]
The “center” column, the “bandwidth” column, and the “level” column in FIG. 13 indicate
filter candidates such as parametric equalization setting candidates to be implemented in one,
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55
some or all loudspeakers of each solution. As mentioned above, various types of equalization may
be explored, including parametric, graphic, parametric, shelving, FIR, and transversal. Statistical
analysis may independently determine the equalization settings implemented for each candidate
loudspeaker. In parametric equalization, the frequency to which the adjustment is applied, eg 60
Hz, is determined by the center frequency. The width of the amplitude adjustment depends on
the bandwidth. For example, if Q = 4, then bandwidth = 15 Hz. The amount of amplitude
adjustment applied, eg -12 dB, depends on the level. Either an increase or a decrease in
amplitude may be applied, but generally a decrease in amplitude is applied. Therefore, in the case
of solution 3, a 6 dB level reduction is applied over Q16 with a center frequency of 27 Hz for the
loudspeakers with position candidate 2 and over Q1 with a center frequency of 41 Hz for
loudspeakers with position candidate 3 Apply 0 dB level reduction. Because the frequency
dependent gain (equalization level) is another kind of gain reduction, one or more of the one or
more loudspeakers by lowering the equalization level setting at one or more frequencies. You
may want to increase the low-frequency acoustical efficiency of your seat.
[0172]
It should be noted that frequency independent or frequency dependent gain and / or delay
reduction may increase the acoustic efficiency and average overall level in certain frequency
bands (such as frequencies below 50 Hz). For example, lowering the volume of one or more
loudspeakers may increase the acoustic efficiency and average overall level. Since the physical
volume of the room covered by the amplitude peak is generally larger than the amplitude dip, the
acoustic efficiency and the average overall level may thus be raised. For example, the peak can
cover 2 to 3 listening places, but the dip can cover 1 listening place. When finding a solution that
reduces the average spatial variation and / or the variation of the spatial average by statistical
analysis, consider the value of the solution that can increase the peak (enforcing interference) at
the expense of dips in the amplitude response It may be implemented in a sound system. Such an
increase in peak to dip at the listening location may be due to the reduction of destructive
interference between the sound waves of the acoustic signal. Therefore, since the acoustic energy
attenuated by the cancellation of waves may be heard before the implementation of the
correction, it may be possible to realize the improvement of the low-frequency acoustic
efficiency.
[0173]
FIG. 14 is an expanded block diagram of block 612 of FIG. 6 showing the implementation of the
values corresponding to the selected solution into the sound system. To implement solution
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56
values corresponding to the number and location of loudspeakers, one or more loudspeakers are
placed at the determined location, as shown in block 1402. Thus, to implement solution 2 of FIG.
13, loudspeakers are placed at position candidates 1, 2 and 3. Similarly, to implement solution 1
with minimal spatial variation, loudspeakers are placed at position candidates 1 and 2.
[0174]
The correction settings may be implemented in the analog domain (eg, gain or equalization) or
digital domain (eg, gain, equalization, or delay) of the sound system 500, and at any convenient
point in the signal path . The gain settings may be implemented in the sound system 500 by
lowering or raising the gain adjustments (commonly referred to as loudness or volume control)
independently at each loudspeaker position, as indicated at block 1404. Therefore, to implement
Solution 2 in FIG. 14, the gain for the loudspeaker of position candidate 1 is lowered by 1 to 6
dB, and the gain of the loudspeaker for position candidate 2 remains 1 or 0, and the loudspeaker
of position candidate 3 is Decrease the gain by 1 to 12 dB. A common way to implement gain
correction is to attenuate or increase the electrical signal that is converted to an acoustic signal
by the transducer, but place multiple loudspeakers that respond to a common electrical signal at
a single location You may go by methods, such as. Alternatively, the correction settings may be
implemented by changing the wiring of the loudspeakers.
[0175]
As shown at block 1406, delay settings such as 10 milliseconds (ms) may be implemented in the
digital domain of the sound system 500 at each loudspeaker position. The implementation of the
delay setting may be after the surround sound or other processor produces a low frequency
output from the input. For example, when a DOLBY DIGITAL 5.1 <(R)> or DTS <(R)> digital signal
is input to a digital surround sound decoder, an LFE (low frequency effect) signal is output. A
delay setting may be introduced before converting this output to the analog domain for
amplification. The delay settings may be implemented in the processor 504 if the processor 504
can output an analog signal, but may be implemented in the loudspeaker if the loudspeaker
electronics accept digital input. Thus, to implement solution 2 of FIG. 13, apply a delay of 0 ms
(no delay) to the loudspeaker of position candidate 1 and apply a delay of 10 ms to the signal
reproduced by the loudspeaker of position candidate 2; No delay is applied to the position
candidate 3 loudspeakers.
[0176]
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57
Equalization settings may be applied to the sound system 500 by applying equalization to each
loudspeaker independently, as shown in block 1408. Parametric equalization is a convenient way
to implement equalization on each loudspeaker. In parametric equalization, settings can be
implemented to select the applied center frequency, bandwidth, and amount of increase or
decrease in amplitude (level). The settings of center frequency, bandwidth and level may be
applied independently to the signal reproduced by each loudspeaker. Thus, to implement solution
2 of FIG. 14, the center frequency, Q and level settings are set to 22 Hz, 1 and -6 dB for
loudspeaker l and 85 Hz for loudspeaker 3 respectively , 1 and -12 dB. Since the loudspeaker of
position candidate 2 has a level setting of 0 dB or 1, no equalization is implemented for this
loudspeaker. The number of steps in block 612 may be smaller than in FIG. 14, or steps not
shown in FIG. 14 may be added.
[0177]
(Example) I examined 7 audio systems. The first five are examples of examining a home theater
system using the above analysis. Of the five home theater systems, three were actual existing
home theater systems, and the remaining two were experimental systems in the listening room.
In each home theater example, the optimized system is compared to the appropriate baseline.
Further, in each home theater example, the measured data are used to predict the results. The
last two are examples of examining a vehicle using the above analysis.
[0178]
Example 1 The first system investigated is not a dedicated home theater. Thus, existing
subwoofer locations are a compromise between low-pass characteristics and aesthetics. FIG. 15
shows the arrangement of rooms in Example 1 at a scale of about 100: 1. Square boxes represent
two subwoofer locations, and circles represent three listening locations. The room shown in FIG.
15 is approximately 27 ′ × 13 ′, one of the walls is angled at 45 °, and the ceiling height is 9
′. The wall and the ceiling are composed of a drywall and a 2 "x 6" embedded bolt. The floor is
made of concrete slabs and covered with ceramic tiles. A considerable portion of the floor is
covered with a partial carpet.
[0179]
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58
FIG. 16 shows the low pass characteristics of the system before applying low frequency analysis.
The thick solid curve in the middle of FIG. 16 is the average amplitude response of the three
listening locations. The thin curve in the middle is the response at each listening location, and the
curve in the upper dashed line is the average spatial variation as a function of frequency, which
is raised to a power of 10 dB for clarity. The lower left text is the metric for this configuration,
with an average spatial variation of 21.4173 dB, a spatial average variation of 23.6992 dB, and
an acoustic efficiency of -12.6886 dB. The text at the bottom right of FIG. 16 is a parameter of
this configuration in which no correction factor has been applied. FIG. 17 is a graph showing
predicted performance after application of low frequency analysis. Table 1 is a comparison of
system performance and parameters before low frequency analysis and after low frequency
analysis.
[0180]
Example 1, in which the angle of one wall is 45 °, indicates that low frequency analysis can be
applied to any room configuration, such as non-rectangular rooms. Furthermore, the system of
Example 1 has a predetermined number and location of subwoofers. The low frequency analysis
of Example 1 is focused on the correction factor to improve the low frequency response of the
system. For example, correction factors for gain, delay, and equalization have been applied to at
least some loudspeakers of Example 1. As shown in FIG. 16, FIG. 17 and Table 1, the results of
this low frequency analysis show that the analysis dramatically reduced the mean spatial
variation and the variation of spatial average, that is, there was an effect, and It indicates that the
acoustic efficiency has increased slightly, which is also effective.
[0181]
Example 2 The second system investigated in Example 2 is a $ 300,000 + dedicated home
theater. FIG. 18 shows the arrangement of rooms in Example 2. The features of the system are a
subwoofer, one at each corner of the room, a video system of the front projection type, and a kick
for the second row of seats. The dimensions of the room are approximately 26 'x 17' and the
ceiling height is 9 '. The two walls are made of concrete blocks, and the two walls consist of
drywall and 2 ′ ′ × 4 ′ ′ embedded bolts. The floor is carpeted on a concrete slab. The
second row of seats is above the 8 "kick, which consists of plywood and a 2" x 4 "stud. The
hallmark of this room is the damping that has been extensively applied to all the walls. FIGS. 19
and 20 show low frequency characteristics before low frequency analysis and after low
frequency analysis. Table 2 is a comparison of system performance before low frequency
09-05-2019
59
analysis and after low frequency analysis.
[0182]
The system of Example 2 has a predetermined number and location of subwoofers, with four
subwoofers at each corner of the room. This low frequency analysis focuses on correction factors
to improve the low frequency response of the system. For example, correction factors for gain,
delay, and equalization have been applied to at least a portion of the loudspeaker of Example 2.
As shown in FIG. 19, FIG. 20, and Table 2, the results of this low frequency analysis show that the
analysis improves the mean spatial variation and the variation of the spatial average and slightly
lowers the acoustic efficiency .
[0183]
Example 3 The third system of Example 3 includes a home theater setup in a family room. FIG.
21 shows the arrangement of rooms in Example 3. The dimensions of the room are about 22 'x
21' and feature a sloping ceiling. The wall and ceiling are comprised of a drywall and a 2 "x 4"
embedded bolt. The floor is made of concrete slabs, surrounded by tiles and carpeted in the
center. The left side wall has several windows that can be covered (and covered) by heavy
curtains. The system originally had two subwoofers at the front of the room. FIG. 22 shows the
low pass characteristics of the original configuration of the system that used subwoofers 1 and 2
on the front of the room before applying low frequency analysis. FIG. 23 shows the low pass
characteristics of the system using subwoofers 1 and 2 after application of low frequency
analysis. Two additional subwoofers were placed at the back of the room and the results of
applying low frequency analysis are shown in FIG. Table 3 compares the performance of the
system before and after the improvement.
[0184]
Example 3 highlights multiple different solution candidates based on the number of subwoofers,
the placement of the subwoofers, and the applied correction factor. FIG. 23 shows the solution
for a subwoofer arranged in the same configuration as FIG. Using low frequency analysis, as
shown in FIG. 23, even with the same configuration, the average spatial variation decreases
dramatically, the variation of the spatial average decreases, and the acoustic efficiency also
decreases. FIG. 24 shows the solution for the subwoofers located at each corner of the room.
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When this low frequency analysis is used, as shown in FIG. 24, the average spatial fluctuation,
the fluctuation of the spatial average, and the acoustic efficiency are greatly improved.
[0185]
Example 4 The system of Example 4 is in a room where there is no partition between adjacent
rooms. FIG. 25 shows the arrangement of rooms in Example 4. The dimensions of the main
chamber are 20 'x 15' and there is no partition between the other room of dimension 17 'x 13'.
Both rooms are 'dropped ceilings' with 8' ceilings and floors are made of carpeted slab concrete.
All walls are composed of drywall and 2 "x 4" embedded bolts. The original configuration used
one subwoofer. FIG. 26 is a graph showing the performance of the system of the original
configuration. Note that this is an exceptionally good listening room, as is evident in the graph of
FIG. Six candidate subwoofer positions were measured, and the best four subwoofer positions
were determined by low frequency analysis. FIG. 27 is a graph showing the performance of the
system after selecting the best four subwoofer locations (subwoofers 1, 2, 4 and 5) by low
frequency analysis and optimizing the parameters of each subwoofer. Table 4 compares the preoptimization and post-optimization setups.
[0186]
Similar to Example 3, Example 4 highlights various solution candidates based on various aspects,
such as the number of subwoofers in the sound system, the placement of the subwoofers, and the
correction factor applied. Through low frequency analysis, the number of subwoofers, the
placement of subwoofers based on candidate subwoofer locations, and / or correction factors
may be determined. Specifically, the system of Example 4 could include up to six subwoofer
candidates. The optimal number of subwoofers was determined to be four by low frequency
analysis. Further, locations 1, 2, 4, and 5 were selected among the six subwoofer location
candidates. By using low frequency analysis, as shown in FIG. 27, the average spatial variation
decreases, the variation of the spatial average increases, and the acoustic efficiency increases.
[0187]
(Example 5) The room of Example 5 is an engineering listening room. FIG. 28 shows the
arrangement of the engineering listening room of Example 5. The dimensions of the room are
approximately 21 'x 24' and the ceiling height is 9 '. The wall and ceiling are a two-layer
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structure comprised of a drywall and a 2 ′ ′ × 6 ′ ′ embedded bolt. The floor is made of
concrete slab and carpeted from wall to wall. Because all room boundaries are relatively rigid,
this room has little attenuation at low frequencies. In this regard, the room of Example 5 is very
different in acoustic characteristics from the room of Example 2 in which the attenuation at low
frequencies is large.
[0188]
As a result of measuring eight candidate subwoofer positions and five listening places in total,
the number of transfer functions became 40. Next, several configurations were simulated, as
shown in detail in FIGS. All results in this example are predicted from 40 transfer functions using
the measured data.
[0189]
FIG. 29 is a graph showing the low pass characteristics of a single subwoofer at the front corner
(Subwoofer 1 of FIG. 28) in a common scenario. This is contrasted to the single best subwoofer
configuration found by the low frequency analysis of FIG. FIG. 31 is a graph showing the low
frequency characteristics of a common “stereo subwoofer” configuration using subwoofers 1
and 3. FIG. 32 is a graph showing the performance of a two subwoofer configuration system with
low frequency analysis limited to finding the best solution for a pair of subwoofers. As shown in
FIG. 32, the best-paired solution uses subwoofers 6 and 7 shown in FIG.
[0190]
FIG. 33 is a graph showing the low frequency characteristics of a configuration using subwoofers
1, 3, 5, and 7 at four corners. FIG. 34 is a graph showing the performance of the same four
subwoofers after application of low frequency analysis. FIG. 35 is a graph showing low-pass
characteristics of configurations using subwoofers 2, 4, 6, and 8 at four midpoints. FIG. 36 is a
graph showing the low pass characteristics of the same four subwoofers after application of low
frequency analysis.
[0191]
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FIG. 37 is a graph showing the low frequency characteristics of the “optimum” configuration
of the four subwoofers. The "optimum" configuration is based on the ranking results of analysis
using spatial variation as the only ranking factor. As shown in FIG. 37, an “optimum”
configuration with four subwoofers includes the subwoofers located at locations 2, 5, 6 and 7.
Furthermore, the "optimum" configuration shown in FIG. 37 includes correction factors for each
subwoofer. Similarly, FIGS. 38 and 39 show the low pass characteristics of another "optimal" four
subwoofer configuration. The “optimum” configurations of FIGS. 38 and 39 are based on the
ranking results of analysis using mean spatial variation and variation of spatial average, and
analysis using mean spatial variation and acoustic efficiency, respectively.
[0192]
FIG. 40 shows the average spatial variation of all simulation configurations investigated for the
Example 5 engineering room. In FIG. 40, points corresponding to representative “stereo
subwoofer” and “four corner” configurations are highlighted on the plot.
[0193]
Table 5 is a comparison of the low pass characteristics of all configurations simulated in Example
5.
[0194]
[0195]
Examining the results in Table 5, low frequency analysis with subwoofer location parameters and
/ or correction factors can improve the low frequency characteristics of the sound system.
Comparing FIG. 29 in which the number of subwoofers is limited to one with FIG. 30, low
frequency characteristics are improved by using low frequency analysis.
This analysis suggests a subwoofer position (position 7) where the average spatial variation and
the variation of the spatial average are reduced and the acoustic efficiency is increased.
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63
[0196]
Comparing FIG. 31 and FIG. 32 in which the number of subwoofers is limited to two, the low
frequency characteristics are improved again by using the low frequency analysis. This analysis
suggests subwoofer positions (positions 6 and 7) and correction factors, with reduced average
spatial and spatial average fluctuations and slightly reduced acoustic efficiency.
[0197]
Comparing FIG. 33 and FIG. 34 in which the number and location of subwoofers are limited (that
is, one subwoofer is disposed at each corner of a room), low frequency characteristics are
improved by using low frequency analysis. This analysis suggests a correction factor that reduces
the average spatial variation and the variation of the spatial average and increases the acoustic
efficiency. Comparing Figure 35 and Figure 36 with limited numbers and locations of subwoofers
(ie, one subwoofer placed at four waypoints in a room), low frequency performance is improved
by using low frequency analysis ing. This analysis suggests a correction factor that reduces the
average spatial variation and the variation of the spatial average and increases the acoustic
efficiency.
[0198]
There are several criteria for ranking the solutions found by low frequency analysis. The ranking
may be based on spatial variation, spatial average variation, acoustic efficiency, or any
combination thereof. 36-38, where the number of subwoofers is limited to four, shows an
example of selecting the location of the subwoofer and the correction factor based on various
ranking criteria. FIG. 36 ranks solutions based only on spatial variations, the preferred solution in
this case being the one with the least spatial variation. Since FIG. 37 ranks solutions based on a
combination of spatial variations and variations of spatial averages, the subwoofer location
selected by the preferred solution is different from the preferred solution of FIG. The spatial
variation is larger than the solution, and the variation of the spatial average is small. Since FIG.
38 ranks the solution based on the combination of spatial variation and acoustic efficiency, the
subwoofer position selected by the preferred solution differs from the preferred solution of FIG.
36, according to the preferred solution of FIG. Large spatial variation and high acoustic
efficiency.
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[0199]
FIG. 41 shows predicted low-pass characteristics of a representative configuration where
subwoofers are placed at four corners based on low-frequency analysis aimed at optimization of
amplitude and delay correction factors. FIG. 42 shows actual low-pass characteristics after
optimization. Comparing FIG. 41 with FIG. 42, the agreement between the predicted low band
characteristics below 70 Hz and the actual low band characteristics is excellent. Therefore, the
low frequency characteristics predicted by the low frequency analysis substantially match the
actual low frequency characteristics.
[0200]
Example 6 As noted above, the teachings herein may apply to sound systems in any type of
space, including vehicles. Examples of vehicles include, but are not limited to, cars and trucks.
One of the problems when "tuning" a vehicle, such as a car, is to match the bass range between
the front and rear seats. A sixth application of this analysis uses a sedan-type vehicle. FIG. 43
shows a graph of the frequency response for 20-200 Hz from the speakers at the bottom in the
front door of the car and on the rear deck. Curves 4302 and 4304 are frequency responses for
the front two seats. Curves 4310 and 4312 are frequency responses for the two rear seats. The
thick black curve 4306 is the average response at all four seats and the thin black curve 4308 is
spatial variation. As shown in FIG. 43, the rear row has about 7 dB less bass than the entire
octave centered at 75 Hz.
[0201]
FIG. 44 shows a graph of frequency response. In FIG. 44, the drive level for the rear deck speaker
has been reduced by 6 dB (indicated as -6 in the "Level" row of FIG. 44). Curves 4402 and 4404
are frequency responses for the front two seats. Curves 4410 and 4412 are frequency responses
for the two rear seats. The thick black curve 4406 is the average response at all four seats and
the thin black curve 4408 is spatial variation. As shown in FIG. 44, the frequency response in the
low tone range is more consistent than FIG. The maximum difference between the front and rear
of the vehicle is about 5 dB and its range is only one-half octave. This is a significant
improvement over the values achieved with the "uniform drive" shown in FIG. Spatial variation is
also improved (from 9.0769 to 3.5033). The average total level at low frequencies has dropped
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by about 0.2 dB, which is due to the lowering of the drive level by about 2.5 dB. The efficiency at
each listening position is improved by approximately 2.3 dB, which is a significant improvement.
Also, the average frequency response is improved. This is consistent with the disclosure content
for the home theater setup described above. Specifically, frequency response and efficiency tend
to improve as seat-to-seat variation decreases. FIG. 44 shows parameters such as level (in dB),
delay (in milliseconds), and equalization (including filter frequency (in Hz), filter gain (in dB) and
filter Q). As shown in FIG. 44, in this speaker arrangement, optimizing the delay and equalization
of the individual speakers did not significantly improve the seat-to-seat variation.
[0202]
The car used in FIGS. 43 and 44 has speakers on the lower part in the front door and on the rear
deck. However, systems with speakers in the four doors and on the rear deck are becoming
commonplace even in cheap cars. Using this system configuration, a pair of additional speakers
were installed at the bottom of the rear door and the optimization routine was run again. FIG. 45
shows the performance of the system before optimization. As shown in FIG. 45, curves 4502 and
4504 are frequency responses for the front two seats, curves 4510 and 4512 are frequency
responses for the two rear seats, and a thick black curve 4506 is The thin black curve 4508 is
the spatial variation, which is the average response for all four seats. FIG. 46 shows the
performance of the system after optimization. As shown in FIG. 46, curves 4602 and 4604 are
frequency responses for the two front seats, curves 4610 and 4612 are frequency responses for
the two rear seats, and a thick black curve 4606 is The thin black curve 4608 is the spatial
variation, which is the average response at all four seats. The variation between the seats is
dramatically reduced (the spatial variation in FIG. 46 is flatter compared to FIG. 45), and the
frequency response at each seat is also flatter. The total output at low frequencies was reduced
by 1 dB, due to the reduction of the total drive level by about 6 dB. That is, the system efficiency
is improved by about 5 dB.
[0203]
Example 7 In addition to sound systems in sedan type vehicles, optimization routines may be
used for sound systems in other types of vehicles, such as sports utility vehicles (SUVs). In the
seventh application of analysis, SUVs are used. The audio system in this SUV has four main
speakers and a single subwoofer. A high pass filter at about 50 Hz was used on the main speaker
to create a "Benchmark". A high pass filter may be used to reduce low frequency signals, the
purpose of which is to (1) reduce the generation of rattle noise in the door (because the main
speaker is mounted on the door), and (2) It is to reduce the possibility of operation outside the
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preferred operating range of the loudspeaker which may cause audible distortion or loudspeaker
damage. A low pass filter was also used at 250 Hz for the subwoofer to create a benchmark. The
electrical gain of each channel was set to the same value. The performance of this benchmark is
shown in detail in FIG. As shown in FIG. 47, curves 4702 and 4704 are frequency responses for
the two front seats, curves 4710 and 4712 are frequency responses for the two rear seats, and a
thick black curve 4706 is The thin black curve 4708 is the spatial variation, which is the average
response at all four seats.
[0204]
The optimization routine was run with the following parameters:
[0205]
The performance with these parameters is shown in FIG.
As shown in FIG. 48, curves 4802 and 4804 are frequency responses for the two front seats,
curves 4810 and 4812 are frequency responses for the two rear seats, and a thick black curve
4806 is The thin black curve 4808 is the spatial variation, which is the average response at all
four seats. FIG. 48 shows the parameters for subwoofer 1 (left front (LF)), subwoofer 2 (right
front (RF)), subwoofer 3 (left rear (LR)), and subwoofer 4 (right rear (RR)). The parameters for the
subwoofer are not shown in FIG. 48 but are shown in the table above. As shown in FIGS. 47 and
48, seat-to-seat variation is reduced by a factor of 6 (average spatial variation is reduced by
approximately 6 to 28.2033 to 4.5895) and the frequency response is flat. Conversion is
remarkable. In addition, the efficiency has been improved by about 3.5 dB.
[0206]
FIG. 49 shows the actual frequency response when using a single microphone at each listening
location. As noted above, acoustic signals (such as frequency response) to be heard at the
listening location may be measured using a single microphone at one, some or all possible
listening locations. (FIG. 48 is the predicted response from the measured raw data. Fig. 50 is a
graph showing the response of a representative microphone array (rather than a single
microphone as used in Fig. 49) located at each listening location in the vehicle. The results shown
in FIGS. 49 and 50 are consistent with the above disclosure of home theater. In particular, the
present approach may improve or optimize system performance over the entire listening area as
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well as system performance at each discrete microphone location.
[0207]
As mentioned above, one of the efforts to improve the frequency response of the system is (1)
frequency response based on at least one metric (flatness, coincidence, efficiency, smoothness,
etc.) for various listening locations To improve the configuration of one, some or all channels,
and (2) to globally improve the frequency response to various listening locations. For example, in
one approach, (1) by selecting the configuration of the audio system (e.g. by selecting the
correction factor (gain, delay, equalization), the location of the speakers, the type of speakers, the
number of speakers etc), Improve system performance as a whole (multiple listenings, if the
frequency response is more consistent across multiple listening locations (e.g., reducing spatial
variation) across multiple listening locations (e.g., reducing spatial variation) Apply global
corrections (such as global equalization) to the system, for example, to flatten the frequency
response to the location. If we try to make a global correction as a whole system without
reducing the variation in frequency response across multiple listening places, the response of the
system at each discrete point (such as a specific listening place) will improve, but at other points
The frequency response may not improve (or may deteriorate).
[0208]
It is possible to further improve the response over the entire listening area by means of a twosided correction method (correction at individual channel level and correction at global level).
Furthermore, the use of correction factors at the individual channel level improved the response
at various listening locations (eg, reducing spatial variations at these listening locations) but not
significantly improving the frequency response (eg, these Even if there are still peaks and valleys,
the frequency response at these listening locations is more consistent, so the global correction
will improve the overall frequency response of the listening area, even if there are still peaks and
valleys). Good.
[0209]
FIG. 51 shows a block diagram of a sound system configuration that can be enhanced or
optimized using the techniques disclosed herein. FIG. 51 shows a seven channel system with
channels in the front left, front center, right front, left side, right side, left back and right back. An
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input 5102 may be used to input seven channels to a plurality of two-way crossovers 5104. The
crossover may include a high pass filter and a low pass filter, where the output of the crossover
will include the output of the high pass filter and the output of the low pass filter. For example,
Out1 of 2 way crossover 5104 may include the output of a high pass filter, and Out2 of 2 way
crossover 5104 may include the output of a low pass filter. A two way crossover may be set up to
allow for total seat-to-seat variation in the low frequency range to be accommodated by the
concept of sound field management including correction factors. Therefore, the crossover can be
chosen such that the timbre and spatial performance in the mid-range frequency range is not
degraded by the correction factors (eg, gain, delay, equalization, etc.). The output (Out2) of the
low pass filter, which may represent bass from all channels, may be sent to the mixer 5106.
These outputs may then be summed by mixer 5106 and input to a single channel. The output
after summation may be enhanced or optimized and then redistributed to the various channels.
[0210]
FIG. 51 shows an example of a two-sided approach in which the audio system includes at least
one individual channel correction and a global correction. As shown in FIG. 51, the output of
mixer 5106 is globally equalized using six bands of parametric equalization 5108. Although a
six-band equalizer is illustrated, the number of bands of the equalizer used may be smaller or
larger. Furthermore, other types of equalizers may be used. The outputs of the six bands of
parametric equalization 5108 may be input to individual channels. As shown in FIG. 51, each
channel may have correction factors such as gain block 5110, delay block 5112, and parametric
equalization block 5114. A single band equalization block may be used. Alternatively, multiple
bands of equalization blocks may be used. Although FIG. 51 shows the order of the gain block
5110, the delay block 5112 and the parametric equalization block 5114, these blocks are merely
one configuration example. The order of these blocks is arbitrary. Additionally, one, some or all
of the channels may include correction factors. As shown in FIG. 51, the front center channel
contains no correction factor. In some audio configurations, the front center speaker is on the
front dashboard, so there is no bass capability (so the dashboard does not vibrate). In such cases,
low frequencies may be filtered out of the channel. Furthermore, the channel may include one,
some or all of these correction factors.
[0211]
As shown in FIG. 51, the output of the correction coefficient may be input to the mixer 5116. A
mixer 5116 may sum the high and low frequencies of the various channels and send them to the
outputs 5118 of the various channels. As shown in FIG. 51, the audio system includes a
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subwoofer, which also receives a low frequency output. As with the other channels, the low
frequency signal of the subwoofer may be optimized with a correction factor.
[0212]
Using sound field management parameters (including correction factors) may reduce the overall
output of the audio system, but may not reduce the overall efficiency. In fact, sound field
management parameters may be used to improve efficiency. Because playback of the bass
requires most of the amplifier power and speaker excursions, it is possible to miniaturize the
channel's amplifier attenuated by the sound field management parameters and / or to shorten
the voice coil. Driving six (or seven) main speakers (approximately the same total cone
excursions) with six (or seven) uniform amplifiers is not optimal in terms of efficiency, so for
example It is possible to make a total audio system with a larger playback volume with respect to
the total amplifier power and cone excursion.
[0213]
In addition, it may be assumed that the frequency response of the front seats is globally
equalized after improving the match between the front and rear seats of the vehicle, which also
improves the frequency response of the rear seats. In fact, one approach is focused on improving
the response of the front seats, and the rear seats may "follow". As a result, there is no need to
sacrifice the performance of the front seat to solve the overall problem of the rear, so both the
front and rear sounds are enhanced.
[0214]
FIG. 52 shows a block diagram of a sound system configuration that can be enhanced or
optimized using the techniques disclosed herein. Once parameters for one audio system are
selected, other audio systems may be configured based on these parameters. For example, in the
case of vehicles, once the parameters for a particular vehicle, such as a particular model, have
been selected, the various audio systems installed on that particular vehicle may be configured
(eg, programmed) with the same parameters, in this case There is no need to retest the vehicle. In
particular, the vehicles of the production line do not necessarily have to be retested, but rather
can be programmed according to the parameters of the audio system previously determined
during the test.
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[0215]
FIG. 52 shows a seven channel audio system. However, the number of audio channels used may
be smaller or larger. The seven channels may be the front left, front center, right front, left side,
right side, left rear, and right rear. The inputs to the seven channels are shown at block 5202.
The seven channels may be sent to high pass filter 5204 and low pass filter 5206. Similar to the
two-way crossover of FIG. 51, high pass filter 5204 and low pass filter 5206 may filter the input
signal to separate it into two different frequency bands. Although only high pass and low pass
filters are shown for each channel, more than two filters may be implemented, and more than
two frequency bands may be provided. The output of low pass filter 5206 may be sent to
summing block 5208. As shown in FIG. 51, an example of the addition block may include a
mixer. The output of summing block 5208 may be sent to equalizer 5210. Equalizer 5210 may
include global equalization of the summed low frequency signal. As mentioned above, global
equalization may involve the application of one or more filters. The output of the equalizer 5210
may be sent to the correction factors for the various channels.
[0216]
As shown in FIG. 52, the correction coefficients may include a delay block 5212, a gain block
5214, and an equalization block 5216. As mentioned above, the order of these blocks is for
illustrative purposes only. As noted above, the disclosed techniques may be used to select
correction factors for individual channels to improve at least one metric of the audio system,
such as reducing seat-to-seat variations in frequency response. Further, equalization may be
applied to higher frequency bands, as shown in equalization block 5218. For example,
equalization block 5218 may focus on equalization of a particular frequency range, such as mid
band frequency. These frequencies may be combined by sending the high frequency and low
frequency outputs to summing block 5220. The output of summing block 5220 may be sent to
the filter. As shown in FIG. 52, the filters for the seven channels are high pass filters 5222. As
shown in FIG. 52, the high pass filter is included for seven speakers. However, the number of
high pass filters used may be less than this, or other filters may be used. As noted above, highpass filters and audio such as car audio systems to reduce door rattle sounds that can cause
audible distortion or speaker damage and the possibility that the speaker will operate out of its
preferred operating range It may be used for the system. Similarly, a low pass filter 5224 may be
included for the signal to the subwoofer. As in the case of a high pass filter, the low pass filter
may reduce the likelihood that the subwoofer will operate out of its preferred range, such as in a
frequency range that is too high. Thus, as a general matter, filters may be selected to improve the
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performance of the filtered loudspeaker. Furthermore, FIG. 52 shows an audio system with seven
main speakers and one subwoofer. The number of main speakers used may be smaller or larger
than this. Furthermore, the number of subwoofers used may be zero or more than one.
[0217]
As noted above, some parameters may be changed to select an improved or optimized audio
configuration. Examples of parameters include, but are not limited to: loudspeaker location,
number of loudspeakers, loudspeaker type, listening location, correction factors (eg, delay,
parametric equalization, frequency independent gain), etc. It is not a thing. Generally, the location
of the loudspeakers in the vehicle is fixed. However, in some cases, the position of the
loudspeaker may be changed (for example, a minute change of the speaker position in the door,
on the rear deck, etc.).
[0218]
In addition to these parameters, it is also possible to filter the signal for one, some or all of the
speakers by means of a crossover filter such as a high pass filter, a low pass filter, a notch filter,
or a combination of such filters Good. In particular, crossover filters 5222, 5224 may add
degrees of freedom that may improve the performance of at least one metric of the audio system.
For example, when emphasis is on seat-to-seat variation, a filter (such as low pass, high pass,
notch, or other type of filter) may be used as another parameter to improve seat-to-seat variation.
As noted above, the transfer function may be measured for one, some or all listening locations.
The predictive transfer function may then be generated by performing statistical analysis using
system parameter values candidates, such as filter value candidates. This statistical analysis may
indicate which filter value candidates improve the metric. (1) The degree of agreement between
the prediction transfer functions (eg, mean spatial variation, mean spatial standard deviation,
mean spatial envelope (ie minimum and maximum), and mean spatial maximum mean) between
multiple listening locations (2 ) Flatness of the prediction transfer function (for example,
variation of spatial average, variation of spatial average standard deviation, variation of spatial
average, and variation of spatial minimum), (3) predicted transfer function (for example, variation
of average level, The difference between the seats of the total sound pressure level against the
standard deviation of the mean level, the envelope of the mean level, and the maximum mean of
the mean level) (4) the efficiency of the prediction transfer function at a single listening location
or multiple listening locations Any statistical analysis described herein may be used, including
(e.g., acoustic efficiency), (5) the output of a predictive transfer function at a single listening
location or multiple listening locations, but only Not intended to be constant. For example, one
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statistical analysis examines seat-to-seat variation. The actual values for the cross-over filter may
then be selected directly from the filter value candidates that indicate an improvement in the
metric, or may be derived from these filter value candidates. These values selected for the
crossover filter may then be used in an audio system such as a car audio system.
[0219]
As high-pass filter value candidates, but for illustrative purposes only, values for 3 dB points (eg
50 Hz, 70 Hz or 100 Hz) and / or the order of the filter (first order, second order or third order)
May be included. Other candidate values may be used for the filter. In the above illustrative
example, nine filter candidates may be analyzed for statistical analysis. Similarly, low pass filter
value candidates may be changed based on 3 dB points (eg, 100 Hz, 140 Hz, or 200 Hz) and / or
the order of the filter (second, third, or fourth). These filter value candidates are also merely
explanatory values. Other candidate values may be used for the filter, or other types of filters
may be used.
[0220]
In statistical analysis, it is determined which filter candidate is to be selected by analyzing filter
candidates such as high pass filter candidates and low pass filter candidates based on at least one
metric (such as variation between seats). Good.
[0221]
The outputs of filters 5222 and 5224 are sent to amplifier 5226.
The outputs of these amplifiers are then sent to respective speakers 5228 including left front,
front center, right front, left side, right side, left back, right back, and subwoofer.
[0222]
In the example above, low frequency analysis was used to significantly improve spatial
variability. Spatial variation was improved 1.5 to 5 times. Spatial variation improvement usually
involves improved spatial average variation and improved acoustic efficiency. One way to
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understand this is to look at the difference between peak and dip in the room's mode response.
The dip tends to be more position dependent than the peak. That is, dips tend to have greater
seat-to-seat variation and greater spatial variation than spatially wider peaks. Thus, as the
optimal solution tends to eliminate dips, the variation of spatial average is improved and the
efficiency factor is improved.
[0223]
Low frequency analysis may be utilized for various subwoofer systems, including two and four
subwoofers. If the subwoofer position and number of subwoofers are predetermined (eg, a set up
home theater system such as Example 1 and Example 2), low frequency analysis may improve
performance. The effectiveness of the low frequency analysis is generally high when subwoofer
position, subwoofer number, and / or correction can be chosen freely, such as the case described
in Example 5.
[0224]
The low frequency analysis may focus on adjusting one, some or all of the above parameters,
including subwoofer location, number of subwoofers, type of subwoofer, correction factor, or any
combination of these. . In addition, low frequency analysis may focus on one, some or all
adjustments of the correction factor, such as simultaneous adjustments of gain, delay, and
filtering. However, it is not necessary to optimize all three of these correction factors to improve
system performance. Finally, although the analysis focuses on low-pass characteristics, any
frequency range may be optimized.
[0225]
The flowcharts of FIGS. 4-12 and 14 may be implemented in hardware or software. When the
process is implemented in software, the software may be stored in one of the hard disk of the
measuring device 520, the external disk 548, the ROM 530 or the RAM 524, or the hard disk of
the computing device 570, the external disk, the ROM or the RAM. It may be resident, or may be
resident in any combination of these. The software may be implemented in logic functions (ie, in
digital form such as digital circuits or source code) or in analog form such as analog sources such
as analog electrical signals, analog sound signals, or analog video signals or analog circuits.
Executable instructions for implementing the instruction) may be included in an ordered list, and
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selectively fetching instructions from a computer-based system, a system including a processor,
or an instruction execution system, apparatus or device, Any computer readable (or signal
carrying) used in an instruction execution system, apparatus or device, such as any other system
capable of executing instructions, or used in connection with such system, apparatus or device It
may be selectively incorporated into the medium. In the context of this document, “computer
readable media”, “machine readable media”, “propagated signal” media, and / or “signal
bearing media” are used by these instruction execution systems, devices or devices, or It is any
means capable of containing, storing, transmitting, propagating, or transferring a program used
by being connected to these systems, devices, or devices. The machine-readable medium is not
limited thereto, and may be selected from, for example, electronic, magnetic, light,
electromagnetic, infrared, or semiconductor systems, devices, devices, or propagation media. As
machine-readable medium, electrical connection (electronic) with one or more wires, portable
computer diskette (magnetic), RAM (electronic), ROM (electronic), erasable programmable read
only memory (EPROM or flash memory) (EPROM or flash memory) Electronics), optical fibers
(light), and portable compact disc read only memory "CD ROM" (light), but is not limited thereto.
Machine-readable media also include paper or other suitable media on which the program can be
printed, because the program is captured electronically, for example by scanning the paper or
other media, for example, optically Or, if necessary, processed in any other suitable manner, and
then stored in computer and / or machine memory.
[0226]
While various embodiments of the invention have been described, it will be apparent to those
skilled in the art that many more embodiments and implementations are possible within the
scope of the invention. Accordingly, the invention is not to be restricted except in light of the
attached claims and the corresponding claims.
[0227]
The invention can be better understood with reference to the following drawings and description.
The components in the figures are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Furthermore, like reference numerals indicate
corresponding parts throughout the respective figures.
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