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JP2016152422

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DESCRIPTION JP2016152422
Abstract: To provide a sound field correction device, a sound field correction method, and a
sound field correction program for obtaining a sufficient sound field correction effect even when
the number of bands of the parametric equalizer is small. A target amplitude characteristic to be
a target of sound field correction by (PEQ) is generated S23, and a plurality of sub target
amplitude characteristics having the same or gentle amplitude characteristics as the target
amplitude characteristic are calculated S24, and the calculated target amplitude characteristics
and A correction amplitude characteristic for correcting a sound field is calculated based on a
plurality of sub target amplitude characteristics, and the frequency bandwidth of the correction
candidate PEQ is calculated S25 to S30 for each sub target amplitude characteristic based on the
correction target candidate group. Calculation of New Sub-Target Amplitude Characteristics The
processing from the processing step S25 is repeated using the sub-target amplitude
characteristics calculated in S32. [Selected figure] Figure 3
Sound field correction device, sound field correction method, and sound field correction program
[0001]
The present invention relates to a sound field correction device, a sound field correction method,
and a sound field correction program.
[0002]
Sound emitted from a speaker (hereinafter referred to as "sound for measuring a sound field".
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) And the sound recorded by the microphone placed at the listening position (hereinafter referred
to as "microphone recorded sound"). The sound field correction apparatus which adjusts the
output level for every frequency band of the sound signal of sound field measurement sound
based on the difference with the sound signal of b) is known. The specific configuration of this
type of sound field correction device is described, for example, in Patent Document 1 and Patent
Document 2.
[0003]
JP, 2007-295528, A JP, 2008-245123, A
[0004]
The sound field correction device described in Patent Document 1 determines the center
frequency based on the frequency at which the gain difference from the target characteristic in
the area included in the frequency range to be corrected is maximum, and the gain at the
determined center frequency The value is determined based on the gain difference from the
target characteristic at the center frequency, and the Q value is further determined from among
predetermined candidates.
However, in the configuration described in Patent Document 1, since the shape of the gain
difference with the target characteristic in the area and the center of gravity are not considered,
it may be difficult to correct the area with high accuracy.
[0005]
The sound field correction device described in Patent Document 2 calculates the signal
correction level for each frequency band from the microphone recording sound, and uses the
calculated signal correction level as a reference in the inflection point of the waveform of the
correction level connected in the frequency band order. The frequency band is divided into a
plurality of groups, and level correction is performed in units of divided groups. The
configuration described in Patent Document 2 is suitable for performing level correction with
high accuracy in that the position of the center of gravity in the group is taken into account, but
depending on the result of the group division processing, for example, the characteristic of the
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parametric equalizer becomes sharp, A problem is pointed out that a sufficient correction effect
can not be obtained with a small number of bands.
[0006]
The present invention has been made in view of such circumstances, and the objective of the
present invention is a sound field correction suitable for obtaining a sufficient sound field
correction effect even when the number of bands of the parametric equalizer is small. Abstract:
An apparatus, a sound field correction method, and a sound field correction program are
provided.
[0007]
A sound field correction apparatus according to an embodiment of the present invention is a
target amplitude characteristic to be a target of sound field correction by a parametric equalizer
based on a predetermined audio signal, and an amplitude characteristic equal to or smoother
than the target amplitude characteristic. Target amplitude calculating means for calculating a
plurality of auxiliary target amplitude characteristics, and corrected amplitude characteristics
calculating means for calculating an corrected amplitude characteristic for correcting a sound
field based on the calculated target amplitude characteristics and the plurality of auxiliary target
amplitude characteristics And setting means for setting a parametric equalizer based on the
calculated corrected amplitude characteristic.
[0008]
In one embodiment of the present invention, the target calculation means calculates the
amplitude characteristic thereof based on the audio signal, performs averaging processing on the
calculated amplitude characteristic with the first resolution, and performs averaging processing.
The target amplitude characteristic may be calculated based on the amplitude characteristic.
Further, the target calculation means calculates the amplitude characteristic based on the audio
signal, and the calculated amplitude characteristic has a resolution equal to or coarser than the
first resolution, and is averaged with a plurality of different types of resolutions. A plurality of
auxiliary target amplitude characteristics may be calculated on the basis of the amplitude
characteristics that have been subjected to an averaging process and averaged with different
resolutions.
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[0009]
In one embodiment of the present invention, the correction amplitude characteristic calculation
unit divides each sub-target amplitude characteristic into a plurality of groups in the frequency
domain based on a predetermined condition, and calculates priorities of the divided groups. The
group having the highest calculated priority is selected for each of the sub target amplitude
characteristics, and the parameter of the correction candidate parametric equalizer is calculated
for each of the sub target amplitude characteristics based on the selected frequency domain
group. The parameter of the parametric equalizer to be corrected may be acquired based on the
parameters of each of the sub-target amplitude characteristics.
In this case, the setting means sets the parametric equalizer based on the parameter of the
parametric equalizer to be corrected.
[0010]
In one embodiment of the present invention, the correction amplitude characteristic calculation
means calculates the amplitude characteristic of the correction candidate for each of the subtarget amplitude characteristics based on the parameter of the parametric equalizer of the
correction candidate, and the calculated amplitude of each correction candidate Among the
characteristics, the parameter having the smallest difference from the target amplitude
characteristic may be acquired as the parameter of the parametric equalizer to be corrected.
[0011]
In one embodiment of the present invention, when the parameter of the parametric equalizer to
be corrected is acquired, the correction amplitude characteristic calculation means calculates a
target amplitude characteristic among the amplitude characteristics of the correction candidate
calculated for each of the sub target amplitude characteristics. The difference between the
amplitude characteristic of the correction target having the smallest difference with the target
and the target amplitude characteristic is calculated as a new target amplitude characteristic, and
the difference between the amplitude characteristic of the correction target and each of the
subtarget amplitude characteristics is newly calculated. If the number of parametric equalizers to
be corrected that have been calculated as sub-target amplitude characteristics of H.sub.2 has not
reached a predetermined number, correction targets are calculated based on the new target
amplitude characteristics and the new plurality of sub-target amplitude characteristics. The
parameter of the parametric equalizer may be further acquired.
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[0012]
Also, in one embodiment of the present invention, parameters of the parametric equalizer
include, for example, the center frequency, gain and frequency bandwidth of the parametric
equalizer.
[0013]
In the sound field correction method according to one embodiment of the present invention, a
target amplitude characteristic to be a target of sound field correction by a parametric equalizer
based on a predetermined audio signal and an amplitude equal to or smoother than the target
amplitude characteristic. A correction amplitude characteristic calculation for calculating a
correction amplitude characteristic for correcting a sound field based on a target calculation step
for calculating a plurality of auxiliary target amplitude characteristics having characteristics and
a calculated target amplitude characteristic and a plurality of auxiliary target amplitude
characteristics The method includes a step and a setting step of setting a parametric equalizer
based on the calculated corrected amplitude characteristic.
[0014]
A sound field correction program according to an embodiment of the present invention is a
program for causing a computer to execute the above-described sound field correction method.
[0015]
According to one embodiment of the present invention, a sound field correction device, a sound
field correction method, and a sound field correction program suitable for obtaining a sufficient
sound field correction effect even when the number of bands of the parametric equalizer is small
Be done.
[0016]
It is a block diagram showing composition of an acoustic system concerning one embodiment of
the present invention.
It is a figure which shows the flowchart of the sound field measurement process performed in the
acoustic system which concerns on one Embodiment of this invention.
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It is a figure which shows the flowchart of the sound field correction | amendment process
performed in the acoustic system which concerns on one Embodiment of this invention.
It is a figure which shows an example of the amplitude characteristic of the impulse response
calculated by process step S22 (calculation of the amplitude characteristic of an impulse
response) of FIG.
It is a figure which shows an example of the normalization amplitude characteristic of the
impulse response calculated by process step S23 (production | generation of a target amplitude
characteristic) of FIG.
It is a figure which shows an example of the target amplitude characteristic produced | generated
by process step S23 (production | generation of a target amplitude characteristic) of FIG.
It is a figure which shows an example of the subtarget amplitude characteristic produced |
generated by process step S24 (production | generation of several subtarget amplitude
characteristics) of FIG. It is a figure which shows the flowchart of process step S25 (group
division process with respect to each subtarget amplitude characteristic) of FIG. It is a figure
which shows typically an example of the positive temporary group selected by process step S25
b of FIG. It is a figure which illustrates the execution result (the result of the group division
process with respect to each subtarget amplitude characteristic) of process step S25 (group
division process with respect to each subtarget amplitude characteristic) of FIG. It is a figure
which shows typically the amplitude characteristic of this group by which priority is calculated
by process step S26 (calculation of the priority of each group) of FIG. It is a figure which shows
an example of the correction object candidate group selected by process step S27 (selection of
the group based on a priority) of FIG. It is a figure which shows each subtarget amplitude
characteristic and the amplitude characteristic of each correction candidate PEQ. It is a figure
which shows each target amplitude characteristic and the amplitude characteristic of each
correction candidate PEQ. It is a figure which shows the new subtarget amplitude characteristic
calculated by process step S32 (calculation of a new subtarget amplitude characteristic) of FIG. It
is a figure which shows the new target amplitude characteristic calculated by process step S33
(calculation of a new target amplitude characteristic) of FIG. The figure which shows the
parameter of each correction candidate PEQ recorded on the internal memory of the control part
concerning one embodiment of the present invention (Drawing 17 (a)), the target amplitude
characteristic, and the figure which shows the correction amplitude characteristic approximated
to this (figure 17 (b)). It is a figure which shows the result of having compared the difference |
error of the number of PEQ bands, and a target amplitude characteristic in each of this prior art
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(patent document 2) and this embodiment.
[0017]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. In the following, as an embodiment of the present invention, an acoustic system
disposed in a vehicle compartment will be described as an example.
[0018]
[Outline of Sound System 1] FIG. 1 is a block diagram showing the structure of a sound system 1
according to an embodiment of the present invention. The sound system 1 according to the
present embodiment corrects a sound field in a listening environment called a vehicle interior,
and more specifically, a signal level for each frequency band of audio signals output to a plurality
of speakers disposed in the vehicle interior Is a system equipped with a sound field correction
function (sound field correction device).
[0019]
The various processes in the sound system 1 are executed by cooperation of software and
hardware provided in the sound system 1. At least the OS (Operating System) part of the
software provided in the sound system 1 is provided as an embedded system, but other parts, for
example, software modules for performing sound field correction, are provided over the network.
It may be provided as an application that can be distributed or held on a recording medium such
as a memory card. That is, the sound field correction function according to the present
embodiment may be a function incorporated in advance in the sound system 1 or a function that
can be added via a network or a recording medium.
[0020]
As shown in FIG. 1, the acoustic system 1 includes a sound field device 10, a microphone 116,
speakers FC, FR, FL, RR, RL, and SW. The speaker FC is a center speaker disposed at the front
center position in the vehicle compartment, the speaker FR is a right front speaker disposed at
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the front right side position in the vehicle compartment, and the speaker FL is disposed in front
of the vehicle compartment The left front speaker is disposed at the left side position of the head,
the speaker RR is a right rear speaker disposed at the rear right side position in the vehicle
compartment, and the speaker RL is disposed at the rear left side position in the vehicle interior
The speaker is a left rear speaker, and the speaker SW is a subwoofer disposed at a rear central
position in the vehicle compartment.
[0021]
The sound field device 10 includes a control unit 100, a display unit 102, an operation unit 104,
a measurement signal generation unit 106, a recording medium reproduction unit 108, a PEQ
(Parametric Equalizer) unit 110, a D / A converter 112, a power amplifier 114, and a microphone
amplifier. 118, an A / D converter 120, a signal recording unit 122, and a calculation unit 124.
[0022]
[Sound Field Measurement Process] FIG. 2 is a diagram showing a flowchart of a sound field
measurement process executed in the sound system 1 according to an embodiment of the
present invention.
Various processes in the acoustic system 1 including the sound field measurement process
shown in this flowchart are executed under the control of the control unit 100. When the control
unit 100 receives a predetermined touch operation on the display unit 102 or a predetermined
operation on the operation unit 104, the control unit 100 causes the display unit 102 to display
an input screen of sound field measurement conditions. Thereby, the sound field measurement
process shown in the present flowchart is started.
[0023]
[S11 (setting of sound field measurement conditions) in FIG. 2] In the main processing step S11,
when the user inputs a sound field measurement condition on the input screen displayed on the
display unit 102, the input sound field is input. Measurement conditions are set. The sound field
measurement condition input here is, for example, the number of channels (or designation of a
speaker to be measured). Since six speakers are mounted in the sound system 1 according to the
present embodiment, the maximum number of channels that can be input is "6". In the present
embodiment, it is assumed that six channels are input.
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[0024]
[S12 in FIG. 2 (Reproduction of Sound Measurement Sound)] In the present processing step S12,
the measurement signal generator 106 generates a predetermined measurement signal. The
generated measurement signal is, for example, an M-sequence code (Maximal length sequence)
or a TSP signal (Time Stretched Pulse), and the processing step S11 (sound field) is performed via
the D / A converter 112 and the power amplifier 114. The speakers FC, FR, FL, RR, RL, and SW
set in the measurement condition setting) are sequentially input at predetermined time intervals.
Thus, predetermined sound field measurement sounds are sequentially reproduced from the
speakers FC, FR, FL, RR, RL, and SW at predetermined time intervals.
[0025]
[S13 in FIG. 2 (Recording of Impulse Response)] In the present embodiment, four seats (driver's
seat, front passenger seat, and a pair of left and right rear seats) are installed in the vehicle
compartment. The microphones 116 are arranged equidistantly from each seat (center position
of the four seats) in order to make an appropriate sound field correction for each occupant of
these four seats. The position at which the microphone 116 is installed changes depending on
the occupant (in other words, the position in the vehicle compartment) to which the effect of the
sound field correction is desired. For example, when it is desired to perform sound field
correction optimal for the driver, the microphone 116 is installed at the driver's seat.
[0026]
In the main processing step S13, the sound field measurement sound reproduced in the
processing step S12 (reproduction of sound field measurement sound) is collected by the
microphone 116, and signal recording is performed via the microphone amplifier 118 and the A
/ D converter 120. It is input to the part 122. The signal recording unit 122 calculates an
impulse response. The impulse response is, for example, multiplied by Fourier-transforming a
reference signal of an inverse characteristic obtained by inverting an input sound field
measurement sound and a measurement signal of a reference (such as a TSP signal) on a time
axis, and multiplying It is obtained by inverse Fourier transform of the value. The calculated
impulse response is recorded in the internal memory 100M of the control unit 100.
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[0027]
[S14 in FIG. 2 (completion determination of sound field measurement processing)] processing
step S12 (reproduction of sound field measurement sound) and S13 (recording of impulse
response) are set in processing step S11 (setting of sound field measurement conditions) It is
executed for each of the speakers. When processing step S12 (reproduction of sound for
measuring the sound field) and S13 (recording of impulse response) are executed for all the
speakers set in processing step S11 (setting of the sound field measurement condition) (S14:
YES) The sound field measurement process shown in this flowchart is completed.
[0028]
[Sound Field Correction Process] FIG. 3 is a view showing a flowchart of a sound field correction
process executed in the sound system 1 according to an embodiment of the present invention.
The sound field correction process shown in FIG. 3 starts upon completion of the sound field
measurement process shown in FIG. 2 and is executed for each speaker.
[0029]
[S21 in FIG. 3 (Setting of Correction Condition)] In the main processing step S21, a setting screen
for setting the correction condition is displayed on the display unit 102. When the user inputs a
correction condition on the setting screen displayed on the display unit 102, the input correction
condition is set. The correction conditions set here are the number of PEQ bands and the
correction frequency range. The number of PEQ bands indicates the number of parametric
equalizers assigned to one speaker, and is “7” in this embodiment. The correction frequency
range indicates the range of the frequency to be corrected, and is set for each speaker based on
the reproducible frequency of the speaker and the like.
[0030]
[S22 in FIG. 3 (calculation of the amplitude characteristics of the impulse response)] In the
present processing step S22, the impulse response recorded in the processing step S13
(recording of the impulse response) is read out and Fourier-transformed by the calculation unit
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124. Thus, the amplitude characteristic of the impulse response in the frequency domain is
calculated. FIG. 4 shows an example of the amplitude characteristic of the impulse response
calculated here. In FIG. 4, the vertical axis and the horizontal axis indicate the signal level (Power
(unit: dB)) and the frequency (Frequency (unit: Hz)), respectively. Power is a square of the
amplitude. Also, human auditory characteristics are logarithmic with respect to frequency. The
frequency on the horizontal axis is logarithmically displayed in accordance with human auditory
characteristics.
[0031]
[S23 (generation of target amplitude characteristics) in FIG. 3] In the present processing step
S23, the calculation unit 124 shifts the amplitude characteristics calculated in processing step
S22 (calculation of the amplitude characteristics of the impulse response) one sample at a time.
While the average value within a predetermined number of samples is calculated, smoothing
(averaging processing) is performed. Here, the averaging process is performed with resolution
equivalent to a 1/3 octave bandwidth known as auditory frequency resolution.
[0032]
Next, the normalized amplitude characteristic of the impulse response is calculated based on the
signal level within the reference bandwidth (500 Hz to 3000 Hz in the present embodiment). FIG.
5 shows an example of the normalized amplitude characteristic of the impulse response
calculated here.
[0033]
The sign of the signal level of the normalized amplitude characteristic of the calculated impulse
response is inverted, and predetermined weighting (for example, weighting of the amplitude
characteristic of the sound field to be generated by the acoustic system 1) is performed. Among
the weighted amplitude characteristics, the amplitude characteristics in the correction frequency
range set in the processing step S21 (setting of correction conditions) are acquired as the target
amplitude characteristics to be the target of the sound field correction. FIG. 6 shows an example
of the target amplitude characteristic generated and acquired here.
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[0034]
[S24 in FIG. 3 (generation of a plurality of sub target amplitude characteristics)] In this
processing step S24, the calculation unit 124 performs the same method as the target amplitude
characteristics generated in processing step S23 (generation of target amplitude characteristics).
Multiple secondary target amplitude characteristics are generated. In the present embodiment,
three types of auxiliary target amplitude characteristics are generated. One is generated by
performing the averaging process with resolution equivalent to 1/1 octave bandwidth, and is
described as “first auxiliary target amplitude characteristic” for the convenience of description.
The other one is generated by performing the averaging process with the same resolution as the
1⁄2 octave band width, and is described as “the second sub-target amplitude characteristic” for
the convenience of description. The remaining one is generated by performing averaging
processing with the same resolution as the 1/3 amplitude bandwidth as the target amplitude
characteristics, and for convenience of explanation, the "third auxiliary target amplitude
characteristics" It is written. As the sub-target amplitude characteristic generated by performing
the averaging process with wide octave bandwidth resolution, the amplitude characteristic
becomes smoother.
[0035]
FIG. 7 (a) shows an example of the first auxiliary target amplitude characteristic, FIG. 7 (b) shows
an example of the second auxiliary target amplitude characteristic, and FIG. 7 (c) shows the third
auxiliary target. An example of an amplitude characteristic is shown. In each of FIGS. 7A to 7C,
the scale of the vertical axis is largely different from that of the other drawings (eg, FIGS. 4 to 6)
for the convenience of describing the three graphs in the drawings. . The third auxiliary target
amplitude characteristic has an amplitude characteristic equal to the target amplitude
characteristic, as shown in FIG. 7 (c). On the other hand, the second auxiliary target amplitude
characteristic has a smoother amplitude characteristic than the target amplitude characteristic
(or the third auxiliary target amplitude characteristic), as shown in FIG. 7 (b). Further, as shown
in FIG. 7A, the first auxiliary target amplitude characteristic has a smoother amplitude
characteristic than the second auxiliary target amplitude characteristic. That is, in the present
process step S24, a plurality of sub target amplitude characteristics having amplitude
characteristics equal to or gentler than the target amplitude characteristics are generated.
[0036]
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[S25 in FIG. 3 (group division processing for each sub target amplitude characteristic)] In this
process step S25, each sub target amplitude generated in processing step S24 (generation of a
plurality of sub target amplitude characteristics) by the calculation unit 124 Group division
processing is performed on the characteristics. FIG. 8 shows a flowchart of group division
processing performed in the present processing step S25.
[0037]
In S25a main processing step S25a of FIG. 8, a provisional group division is performed by the
sign of the signal level for each of the sub target amplitude characteristics generated in the
processing step S24 (generation of a plurality of sub target amplitude characteristics). More
specifically, the secondary target amplitude characteristics are divided into groups of positive or
negative signal levels for each successive frequency range (ie, frequency range without signal
level inversion).
[0038]
In S25b, main processing step S25b of FIG. 8, one temporary group is selected from the
temporary group groups temporarily divided in the processing step S25a.
[0039]
In step S25c in FIG. 8, a detection process is performed on a predetermined singular point in the
temporary group selected in the process step S25b.
If no singular point is detected in the main processing step S25c (S25c: NO), the temporary group
selected in the processing step S25b is determined as the main group, and the process proceeds
to the processing step S25j. If a singular point is detected in the main processing step S25c
(S25c: YES), the process proceeds to the processing step S25d. In this case, at least one local
minimum is detected in the positive temporary group (frequency region where positive signal
levels are continuous), and at least one maximum is detected in the negative temporary group
(frequency regions where negative signal levels are continuous). The value is detected.
[0040]
S25d of FIG. 8 In step S25d, the singular point detected in processing step S25c is selected to
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have the smallest absolute value.
[0041]
In step S25e of FIG. 8, the provisional group is provisionally divided at the boundary of the
singular point selected in step S25d.
[0042]
In S25f main processing step S25f of FIG. 8, the absolute value which is the maximum in each
temporary division group provisionally divided in the processing step S25e is detected.
[0043]
In S25g main processing step S25g in FIG. 8, the absolute value of the singularity point selected
in processing step S25d (the absolute value which becomes the smallest in the temporary group)
and each temporary division group detected in processing step S25f It is determined whether or
not the difference from the maximum absolute value is greater than or equal to a predetermined
threshold value.
[0044]
S25h of FIG. 8 This process step S25h is executed when it is determined in the process step S25g
that the difference is equal to or more than the predetermined threshold (S25g: YES).
In the main processing step S25h, the temporary group is divided at the singular point selected
in the processing step S25d, and is determined as two main groups.
[0045]
S25i in FIG. 8 This process step S25i is executed when it is determined that the difference is less
than the predetermined threshold in process step S25g (S25g: NO).
In the main processing step S25i, the singular point selected in the processing step S25d is
excluded from the detection targets in the processing step S25c.
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Next, the group division processing shown in the present flowchart returns to the processing step
S25c.
[0046]
In S25j main processing step S25j of FIG. 8, whether or not the processing after the processing
step S25c (processing to be determined as the main group) has been executed for all temporary
groups divided in the processing step S25a. Is determined.
The group division processing shown in this flowchart returns to the processing step S25b when
an unprocessed provisional group remains (S25j: NO), and when the processing for all the
provisional groups is completed (S25j: YES), finish.
[0047]
FIG. 9 schematically shows an example of the positive temporary group selected in the
processing step S25b. In the example of FIG. 9, the minimum values min1 and min2 are detected
in processing step S25c. At processing step S25d, a local minimum value min2 having a small
absolute value is selected. In processing step S25e, the provisional group is provisionally divided
at the boundary of the minimum value min2. In the processing step S25f, maximum values max1
and max2 that become maximum are detected in each of the temporarily divided temporary
division groups G1 and G2. At processing step S25g, it is determined whether or not any of the
difference value between the minimum value min2 and the maximum value max1 and the
difference value between the minimum value min2 and the maximum value max2 is equal to or
greater than a predetermined threshold value. In the example of FIG. 9, since any difference
value is equal to or greater than the predetermined threshold value, the provisional division
groups G1 and G2 are determined as the main group.
[0048]
FIG. 10 exemplifies the result of the group division processing for each sub-target amplitude
characteristic when the threshold used for the determination in the processing step S25g is 1. In
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each of FIGS. 10 (a) to 10 (c), the amplitude characteristic indicated by the solid line is the main
group whose signal level is positive, and the amplitude characteristic indicated by the broken line
is the main group whose signal level is negative. FIGS. 10 (a), 10 (b) and 10 (c) show the results
of the group division process for the first, second and third sub target amplitude characteristics,
respectively. As shown in FIGS. 10 (a), 10 (b) and 10 (c), the first, second and third auxiliary
target amplitude characteristics are 9, 14, and 15 respectively. The book is divided into groups.
[0049]
[S26 of FIG. 3 (calculation of priority of each group)] In the present processing step S26, the
calculation unit 124 calculates the priority of the present group for each sub target amplitude
characteristic based on the signal level of the present group. FIG. 11 schematically shows the
amplitude characteristic of the present group whose priority is calculated. In FIG. 11, frequencies
corresponding to the respective signal levels g n -1, g 0,... G k, g k +1 are defined as f n -1, f 0,... F
k, f k + 1. In this case, the priority of each main group of each sub target amplitude characteristic
is calculated by the following equation 1. (Expression 1) <img class = "EMIRef" id = "391220124000003" />
[0050]
[S27 (Selection of Group Based on Priority) in FIG. 3] In this process step S27, the calculation unit
124 calculates the priority in the process step S26 (calculates the priority of each group) based
on the result of the highest priority. This group is selected in each subtarget amplitude
characteristic. Hereinafter, for convenience of explanation, the main group with the highest
priority in the first sub target amplitude characteristic is given the code Gr1 / 1, and the main
group with the highest priority in the second sub target amplitude characteristic is the code Gr1
The third sub target amplitude characteristic is given the code G r1 / 3 to the highest priority
group.
[0051]
The main groups G r1 / 1, G r1 / 2, and G r1 / 3 selected in the main processing step S27
become groups of correction target candidates. 12 (a), 12 (b), and 12 (c) respectively show
examples of correction target candidate groups Gr1 / 1, Gr1 / 2, and Gr1 / 3 selected in the main
processing step S27. Show.
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[0052]
[S28 in FIG. 3 (calculation of center frequency)] In the main processing step S28, the calculation
unit 124 corrects the candidate PEQ based on the correction target candidate group selected in
the processing step S27 (group selection based on priority). The center frequency (the position of
the center of gravity) of is calculated for each sub target amplitude characteristic. When the
signal level and the frequency in the correction target candidate group are defined as shown in
FIG. 11, the center frequency of the correction candidate PEQ is calculated by the following
equation 2. (Expression 2) <img class = "EMIRef" id = "391201214-00004" />
[0053]
[S29 in FIG. 3 (calculation of gain)] In the main processing step S29, the calculation unit 124
calculates correction candidate PEQ based on the correction target candidate group selected in
processing step S27 (group selection based on priority). A gain is calculated for each sub-target
amplitude characteristic. When the signal level and the frequency in the correction target
candidate group are defined as shown in FIG. 11, the gain of the correction candidate PEQ is
calculated by the following expression 3. (Expression 3) <img class = "EMIRef" id = "391220124000005" />
[0054]
[S30 in FIG. 3 (Calculation of Frequency Bandwidth)] In the main processing step S30, the
calculation unit 124 makes correction candidates based on the correction target candidate group
selected in the processing step S27 (group selection based on priority). The frequency bandwidth
of PEQ is calculated for each sub-target amplitude characteristic. When the signal level and the
frequency in the correction target candidate group are defined as shown in FIG. 11, the
frequency bandwidth of the correction candidate PEQ is calculated by the following equation 4.
(Expression 4) <img class = "EMIRef" id = "391220124-000006" />
[0055]
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By calculating the center frequency, gain and frequency bandwidth of the correction candidate
PEQ, the amplitude characteristic of the correction candidate PEQ can be obtained. FIG. 13A
shows a first auxiliary target amplitude characteristic (thick solid line) and an amplitude
characteristic (thin solid line) of the first correction candidate PEQ generated from the first
auxiliary target amplitude characteristic. FIG. 13 (c) shows the second auxiliary target amplitude
characteristic (thick solid line) and the amplitude characteristic (thin solid line) of the second
correction candidate PEQ generated from the second auxiliary target amplitude characteristic.
Shows the third sub target amplitude characteristic (thick solid line) and the amplitude
characteristic (thin solid line) of the third correction candidate PEQ generated from the third sub
target amplitude characteristic.
[0056]
[S31 in FIG. 3 (selection of correction target PEQ)] In the main processing step S31, the
calculation unit 124 compares the target amplitude characteristics with the amplitude
characteristics of the first to third correction candidates PEQ to obtain the target amplitude
characteristics. The correction candidate PEQ having the smallest difference between the and is
selected as one of the PEQs to be corrected. The parameters (center frequency, gain and
frequency bandwidth) of the correction target PEQ selected as one of the correction target PEQs
are recorded in the internal memory 100M of the control unit 100.
[0057]
14 (a), 14 (b) and 14 (c) respectively show the target amplitude characteristics (thick solid line)
and the amplitude characteristics (thin solid line) of the first, second and third correction
candidate PEQs. Show. In the example of FIG. 14, the correction candidate PEQ having the
smallest difference from the target amplitude characteristic is the second correction candidate
PEQ. Therefore, here, the second correction candidate PEQ is selected as one of the correction
target PEQs.
[0058]
[S32 in FIG. 3 (calculation of a new sub-target amplitude characteristic)] In the present
processing step S32, the amplitude characteristics and the respective characteristics of the
correction target PEQ selected in the processing step S31 (selection of correction target PEQ) by
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the calculation unit 124 The difference from the sub target amplitude characteristic is calculated
as a new sub target amplitude characteristic. FIG. 15 (a) shows the difference between the
amplitude characteristic of the correction target PEQ and the first auxiliary target amplitude
characteristic (new first auxiliary target amplitude characteristic), and FIG. 15 (b) shows the
amplitude of the correction target PEQ The difference between the characteristic and the second
auxiliary target amplitude characteristic (new second auxiliary target amplitude characteristic) is
shown in FIG. 15C, and the difference between the amplitude characteristic of the correction
target PEQ and the third auxiliary target amplitude characteristic is shown in FIG. (A new third
sub-target amplitude characteristic) is shown.
[0059]
[S33 in FIG. 3 (calculation of a new target amplitude characteristic)] In the main processing step
S33, the amplitude characteristic and target amplitude of the correction target PEQ selected in
the processing step S31 (selection of correction target PEQ) by the calculation unit 124 The
difference from the characteristic is calculated as a new target amplitude characteristic. FIG. 16
shows the difference between the amplitude characteristic of the correction target PEQ and the
target amplitude characteristic (new target amplitude characteristic).
[0060]
[S34 (end determination) in FIG. 3] In the main processing step S34, the number of correction
target PEQs in which the parameter is recorded by execution of the processing step S31
(selection of the correction target PEQ) by the calculation unit 124 It is determined whether the
number of PEQ bands set in (setting of conditions) has been reached. The sound field correction
process shown in this flowchart ends when it is determined that the number of correction target
PEQs recorded in the internal memory 100M of the control unit 100 has reached the number of
PEQ bands (S34: YES), and the correction targets If it is determined that the number of PEQs has
not reached the number of PEQ bands (S34: NO), processing returns to processing step S25
(group division processing for each sub target amplitude characteristic), and processing step S32
(of new sub target amplitude characteristic) The processing after the processing step S25 is
repeated using the new sub target amplitude characteristic calculated in the calculation) and the
new target amplitude characteristic calculated in the processing step S32 (calculation of a new
target amplitude characteristic).
[0061]
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Every time the processing steps S25 to S34 loop, the parameters (center frequency, gain and
frequency bandwidth) of the correction target PEQ are sequentially stored in the internal
memory 100M of the control unit 100 while the target amplitude characteristic and each sub
target amplitude characteristic are updated. It is recorded.
[0062]
The PEQ unit 110 is an IIR (Infinite Impulse Response) filter, and includes a plurality of
equalizers capable of adjusting parameters (center frequency, gain, and frequency bandwidth).
By setting the parameters of each correction target PEQ recorded in the internal memory 100M
of the control unit 100 in the PEQ unit 110, a correction amplitude characteristic approximating
the target amplitude characteristic is set. The PEQ unit 110 adjusts the signal level for each
frequency band according to the correction amplitude characteristic with respect to an audio
signal such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) read by the recording
medium reproducing unit 108. Correct the sound field.
[0063]
FIG. 17 (a) shows parameters of each correction target PEQ recorded in the internal memory
100M of the control unit 100, and FIG. 17 (b) shows target amplitude characteristics (thick solid
lines) and correction amplitude characteristics (approximately) Thin solid line). As shown in FIG.
17 (b), the correction amplitude characteristic approximates the target amplitude characteristic
and is corrected with high accuracy.
[0064]
Thus, according to one embodiment of the present invention, rough (macro) correction to fine
(micro) correction are sequentially performed, which is sufficient even when the number of
bands of PEQ is small. Sound field correction effects can be obtained. Further, since the sound
field correction is performed with a simple configuration, it is suitable for shortening the
processing time of the sound field correction.
07-05-2019
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[0065]
FIG. 18A shows an example of the target amplitude characteristic. Further, in FIG. 18 (b), in the
case where the target amplitude characteristic is as shown in FIG. 18 (a) in each of the
conventional (patent document 2) and the present embodiment, the number of PEQ bands and
the target amplitude characteristic are The result of comparing the errors is shown. As shown in
FIG. 18B, in the present embodiment, it is understood that the error of the sound field correction
is reduced by about 15 to 25% as compared with the conventional case. That is, in the present
embodiment, it is understood that a sufficient sound field correction effect can be obtained even
when the number of bands of PEQ is small.
[0066]
The above is a description of an exemplary embodiment of the present invention. Embodiments
of the present invention are not limited to those described above, and various modifications are
possible within the scope of the technical idea of the present invention. For example, the contents
of the embodiment of the present application also include the contents in which the embodiment
etc. or the obvious embodiment etc. which are clearly illustrated in the specification are
appropriately combined.
[0067]
In the above embodiment, the acoustic system corrects the sound field in the passenger
compartment, but the invention is not limited thereto. In another embodiment, the acoustic
system may correct the sound field in other specific spaces, such as in a home. Also, while the
sound system comprises a plurality of speakers in the above embodiment, it may comprise a
single speaker in another embodiment.
[0068]
Further, in the above embodiment, although the single device (sound field device 10) has the
sound field measurement function and the sound field correction function, the present invention
is not limited to this. In another embodiment, the sound system may be composed of a plurality
of devices, and the sound field measurement function and the sound field correction function
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may be provided in separate devices constituting the system. As an example, a configuration may
be considered in which an information processing terminal such as a smartphone performs
sound field measurement, and a device such as a vehicle-mounted device performs sound field
correction based on the measurement result.
[0069]
Reference Signs List 1 sound system 10 sound field device 100 control unit 100M internal
memory 102 display unit 104 operation unit 106 measurement signal generation unit 108
recording medium reproduction unit 110 PEQ unit 112 D / A converter 114 power amplifier
116 microphone 118 microphone amplifier 120 A / D converter 122 Signal recording unit 124
Calculation unit FC, FR, FL, RR, RL, SW Speaker
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