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JP2008245123

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DESCRIPTION JP2008245123
A frequency characteristic is accurately corrected to a target characteristic. SOLUTION: A
parametric equalizer 9 which performs level adjustment for each input frequency band according
to the frequency band, and a normalized band signal level before signal level correction is
obtained from the sound collected by the microphone 30, and a predetermined order is obtained
for each frequency band. The signal correction level corresponding to the target frequency band
for this time is determined based on the normalized band signal level after correcting the signal
level with the signal correction level for another frequency band already calculated when
obtaining the signal correction level in And a control unit 1 configured to set the parametric
equalizer 9 to perform signal level correction of the audio signal based on the signal correction
level for each frequency band. [Selected figure] Figure 1
Sound field correction device, sound field correction method and control program
[0001]
The present invention relates to a sound field correction apparatus, a sound field correction
method, and a control program, and more particularly to a control method thereof.
[0002]
Conventionally, when the user selects attribute information such as a speaker position and a
listening position according to a vehicle manufacturer's name, vehicle type, grade, etc., sound
field correction data corresponding to the selected attribute information is displayed on a CDROM or the Internet. A sound field correction apparatus has been proposed which adjusts the
output level of each sound signal to be output to each speaker based on the sound field
correction data acquired via the sound field correction data (see, for example, Patent Document
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1
1).
[0003]
Also, a microphone is placed at the listening position, and sound field correction data of the audio
signal output to each speaker is calculated based on the difference between the audio signal
output to the speaker and the audio signal based on the audio collected by the microphone Also,
a sound field correction device has been proposed that adjusts the output level of the audio
signal output to each speaker for each frequency band (see, for example, Patent Document 2).
Japanese Patent Application Publication No. 2003-153400 Japanese Patent Application
Publication No. 5-184000
[0004]
However, the technology described in Patent Document 1 has a problem that the output level for
each frequency band can not be adjusted when there is no sound field correction data
corresponding to a vehicle equipped with the sound field correction device. The
[0005]
Further, in the technology described in Patent Document 2 above, since the output level for each
frequency band is adjusted centering on a plurality of predetermined frequency points, only the
output level of the frequency band apart from that frequency point is adjusted. In some cases, it
is difficult to accurately correct the level characteristic of each frequency band to the target
characteristic.
[0006]
Therefore, an object of the present invention is made in view of the above-mentioned
circumstances, and a sound field correction device, a sound field correction method, and a
control program capable of accurately correcting level characteristics of each frequency band to
target characteristics. To provide.
[0007]
In order to solve the above-mentioned problems, sound emitted from the speaker is collected by
a microphone based on a predetermined measurement signal, and a sound field is used to
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perform signal level correction of an audio signal to be output to the speaker based on the
collected sound. A correction device, a parametric equalizer for performing level adjustment on
the input audio signal for each frequency band, a normalized band signal level calculation unit
for obtaining a normalized band signal level before signal level correction from the sound
collected by the microphone; When obtaining the signal correction level in the predetermined
order for each frequency band, the frequency to be the current target based on the normalized
band signal level after correcting the signal level with the signal correction level for the other
frequency band already calculated. A correction level calculation unit for calculating a signal
correction level corresponding to a band; Based on the level it is characterized by comprising a
setting unit that sets the parametric equalizer in order to perform signal level correction of the
audio signal.
[0008]
According to the above configuration, the normalized band signal level calculation unit obtains
the normalized band signal level before the signal level correction from the sound collected by
the microphone.
When the correction level calculation unit determines the signal correction level in a
predetermined order for each frequency band, the correction level calculation unit uses the
normalized band signal level after correcting the signal level with the signal correction level for
another frequency band already calculated. The signal correction level corresponding to the
target frequency band is calculated.
The setting unit sets the parametric equalizer to perform signal level correction of the audio
signal based on the signal correction level for each frequency band.
As a result of these, the parametric equalizer adjusts the level of the input audio signal according
to the setting state of the setting unit for each frequency band.
Therefore, signal correction levels corresponding to a plurality of frequency bands are not
canceled and not corrected.
[0009]
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In this case, the correction level calculation unit sets the normalized band signal level before
signal level correction calculated by the normalization band signal level calculation unit as Y (0),
and the signal correction level for the (n + 1) th frequency band. In determining the n-th signal
correction level, the normalized band signal level used for the frequency band is Y (n), the signal
correction level obtained for the n-th frequency band is Z (n), and (n + 1) Assuming that the
normalized band signal level used for the frequency band for which the signal correction level is
to be calculated is Y (n + 1), Y (n + 1) = Y (n) + Z (n) [where n = 0, 1, 2] ,..., Z (0) = 0] may be
calculated as the signal correction level.
[0010]
The setting unit divides the frequency band of the audio signal into groups based on an inflection
point of the waveform of the signal correction level and a predetermined threshold level, and
causes the level correction to be performed on a group basis. It is also good.
Further, the setting unit may obtain the barycentric position of the waveform of the signal
correction level in the group, and set the center frequency and gain of the parametric equalizer
based on the frequency of the barycentric position and the correction signal level. .
Furthermore, the setting unit sets the passband width of the parametric equalizer based on a
combination of the gain of the parametric equalizer set based on the position of the center of
gravity in the group and the frequency bandwidth of the group. You may do so. Further, the
predetermined measurement signal may use pink noise.
[0011]
In addition, using a parametric equalizer that performs level adjustment for the input audio
signal for each frequency band, the sound emitted from the speaker is collected by the
microphone based on a predetermined measurement signal, and the speaker is collected based
on the collected sound A sound field correction method for performing signal level correction of
an audio signal to be output to a sound signal, a normalized band signal level calculating process
of obtaining a normalized band signal level before signal level correction from sound collected by
the microphone; When obtaining the signal correction level in a predetermined order, based on
the normalized band signal level after correcting the signal level based on the signal correction
level for the other frequency band already calculated, A correction level calculation process for
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calculating a corresponding signal correction level; and the signal correction level for each
frequency band Is characterized by comprising a, a setting process of setting the parametric
equalizer in order to perform signal level correction of the audio signal based on. In addition, a
parametric equalizer is provided to adjust the level of the input audio signal for each frequency
band, and the sound emitted from the speaker is collected by the microphone based on a
predetermined measurement signal, and the collected sound is used. A control program for
controlling by a computer a sound field correction device that performs signal level correction of
an audio signal to be output to a speaker, obtaining a normalized band signal level before signal
level correction from the sound collected by the microphone, When obtaining the signal
correction level in a predetermined order for each frequency band, this time target is obtained
based on the normalized band signal level after correcting the signal level based on the signal
correction level for the other frequency band already calculated. Calculating the signal correction
level corresponding to the frequency band, and To set the parametric equalizer in order to
perform signal level correction of the audio signal based on the Le, it is characterized by. In this
case, the control program may be recorded on a computer readable recording medium.
[0012]
According to the present invention, the frequency characteristic can be corrected to the target
characteristic with high accuracy.
[0013]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
FIG. 1 is a block diagram showing the main configuration of the sound field correction apparatus
100. As shown in FIG. The sound field correction apparatus 100 is incorporated in an on-vehicle
audio apparatus, a car navigation apparatus, or the like, and the signal level for each frequency
band of the audio signal to be output to the speaker group 20 composed of a plurality of
speakers disposed in the vehicle compartment. adjust. The sound field correction apparatus 100
includes a control unit 1, an operation unit 2, a display unit 3, a measurement signal generation
unit 4, a recording medium reproduction unit 10, a PMEQ 9, a D / A converter 11, a power
amplifier 5, a microphone amplifier 6, an A / D. The converter 12, the signal recording unit 7 and
the calculation unit 8 are provided.
[0014]
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The control unit 1 functions as a computer that controls the entire system of the sound field
correction apparatus 100, and includes a central processing unit (CPU), a read only memory
(ROM) for storing a control program executed by the CPU, and various data. It has a RAM
(Random Access Memory) etc. which is temporarily stored. The operation unit 2 includes an
operation switch operated by the user, and inputs an operation instruction from the user via the
operation switch to notify the control unit 1. The display unit 3 includes a liquid crystal display
device, and displays various images under the control of the control unit 1.
[0015]
The measurement signal generator 4 outputs a pink noise digital audio signal (measurement
signal) to the power amplifier 5. The recording medium playback unit 10 includes a CD or DVD
playback device, reads data recorded on the CD or DVD according to the control of the control
unit 1, performs decoding processing, and outputs a digital signal of audio or video to a
parametric equalizer unit. (Hereafter, it is called PMEQ. Output to 9).
[0016]
PMEQ 9 is a parametric equalizer that includes a plurality of systems of IIR filters constituting a
plurality of systems of peaking equalizers, and the center frequency, gain, and frequency
bandwidth can be adjusted for each system, and measurement signal generation unit 4 or
recording medium reproduction unit 10. Perform level adjustment for each frequency band of
the digital audio signal output from 10. The PMEQ 9 in the present embodiment includes a
plurality of peaking equalizers that can correspond to a plurality of frequency bands. The D / A
(Digital / Analog) converter 11 converts the digital audio signal that has passed through the
PMEQ 9 into an analog audio signal and outputs the analog audio signal to the power amplifier 5.
The power amplifier 5 amplifies the analog audio signal output from the D / A converter 11 and
outputs the amplified signal to the speaker group 20. The power amplifier 5 in the present
embodiment is a multichannel power amplifier corresponding to a plurality of channels.
[0017]
The microphone amplifier 6 amplifies an analog audio signal output from the microphone 30
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connected to the sound field correction device 100 and outputs the amplified signal to the A / D
converter 12. The sound signal of pink noise that is produced is input from the microphone 30,
and the input sound signal of pink noise is amplified and then output to the A / D converter 12.
The A / D converter 12 converts an analog voice signal of pink noise amplified by the
microphone amplifier 6 into a digital voice signal and outputs the digital voice signal to the
signal recording unit 7. The signal recording unit 7 extracts the signal level for each reference
bandwidth (1/3 octave) of the pink noise collected by the microphone 30 by 31 band pass
filtering processes for each 1/3 octave, and the measurement time Averaging processing is
performed and stored in the RAM in the control unit 1 as signal level data. In addition, the signal
level data of the frequency range of 20 Hz-20 kHz which a person can listen to can be extracted
by comprising 31 band pass filters every 1/3 octave. The calculation unit 8 performs various
calculation processing on the signal level data of 20 Hz to 20 kHz stored by the signal recording
unit 7 to generate sound field correction data which is setting information of the center
frequency, gain and frequency bandwidth of the PMEQ 9 Output to control unit 1.
[0018]
The speaker group 20 in the present embodiment is, as shown in FIG. 2, disposed in front of the
front right speaker 21 disposed on the front right side of the driver's seat 41 of the vehicle 40,
between the driver's seat 41 and the assistant's seat 42. Center speaker 22, front left speaker 23
disposed on the front left side of passenger seat 42, subwoofer 24 disposed in the rear center of
rear seat 43, rear right speaker 25 disposed on the rear right side of rear seat 43, and rear seat
43 And a rear left speaker 26 disposed on the rear left side of. The microphone 30 collects pink
noise emitted from the speakers 21 to 26 disposed at the listening position and constituting the
speaker group 20. In the present embodiment, the driver's seat 41 and the assistant's seat 42 are
provided. And the center of the rear seat 43. In addition, this arrangement is a position in the
case of performing sound field correction appropriate for the occupants of the driver's seat 41,
the assistant driver's seat 42 and the rear seat 43. For example, in the case of performing sound
field correction optimal for the driver Placed at the listening position of the person. Next, prior to
describing the operation of the embodiment, the operation principle of the embodiment will be
described. When performing sound field correction, automatically measure the acoustic
characteristic between the speaker and the listening point, and based on the acoustic
characteristic measurement data, the parameters (center frequency, gain, bandwidth) of the
peaking equalizer (PEQ) configured with an IIR filter Can be calculated automatically and
frequency correction can be performed.
[0019]
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FIG. 3 is an explanatory diagram of an example of acoustic characteristic measurement data. In
the following description, in order to simplify the description, a case where sound field correction
is performed using four peaking equalizers PEQ1 to PEQ4 will be described. For example, in the
case where the input acoustic characteristic measurement data is as shown in FIG. 3 and it is
intended to correct it to make it a flat acoustic characteristic, the sound corresponding to four
peaking equalizers PEQ1 to PEQ4 for four frequency bands is to be obtained. Field correction
data is generated, these are combined and then applied.
[0020]
FIG. 4 is an explanatory view of an example of the filter characteristic. FIG. 5 is an explanatory
view of a combined characteristic of the filter characteristic of FIG. As shown in FIG. 4, the signal
correction levels corresponding to the sound field correction data for the four peaking equalizers
PEQ1 to PEQ4 are the signal correction levels SP1 to SP4, respectively. The total filter
characteristics obtained by these are, as shown in FIG. 5, in the state where the characteristics of
the four frequency bands are combined. The vertical axes in FIG. 4 and FIG. 5 are correction
gains. As shown in FIG. 5, the correction to the positive side near the frequency 80 Hz of the
third peaking equalizer PEQ3 at the signal correction level SP3 in FIG. 4 is the correction to the
negative side of the peaking equalizer PEQ1 at the signal correction level SP1 in FIG. Correction
is not made for dips (drops in signal level) near 80 Hz (indicated by arrows in the figure)
included in the original acoustic characteristic measurement data shown in FIG. Become. In other
words, even if a combination of sound field correction data is applied, the correction may not be
performed. Although the above description is an example of correction with four peaking
equalizers, even if the number of frequency bands of the parametric equalizer is increased,
correction is not performed for dips near 80 Hz.
[0021]
Therefore, in the present embodiment, when obtaining the signal correction level in a
predetermined order (for example, in the order of signal levels) for each frequency band, a
normal after correcting the signal level with the signal correction level for another frequency
band already calculated. The signal correction level corresponding to the target frequency band
of this time is calculated on the basis of the quantization band signal level, and parameters for
each frequency band of the parametric equalizer are set. More specifically, assuming that the
normalized band signal level before signal level correction is Y (0) from the sound collected by
the microphone and the signal correction level is calculated for the (n + 1) th frequency band, the
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nth signal correction The normalized band signal level used for the frequency band whose level
is to be determined is Y (n), the signal correction level obtained for the nth frequency band is Z
(n), and the frequency band for which the (n + 1) th signal correction level is obtained Y (n + 1) =
Y (n) + Z (n) [where n = 0, 1, 2,..., Z (0) = 0, where Y (n + 1) is the normalized band signal level
used for As a next signal correction level, the PEQ filter characteristic band signal level Z (n + 1)
is calculated. As a result, with respect to frequency components that are originally to be
corrected, the signal correction levels of the peaking equalizers are reflected without being offset,
and all corrections can be performed, and the sound field correction data is synthesized. The
frequency characteristic can be corrected to the target characteristic with high accuracy, as
compared to the case of application after that.
[0022]
Next, the operation of the sound field correction apparatus 100 will be described. FIG. 6 is a
flowchart showing the sound field measurement process of the embodiment. The sound field
correction apparatus 100 performs a sound field measurement process of measuring a sound
field characteristic in the vehicle compartment under the control of the control unit 1 and a
sound field of generating data for sound field correction based on the measured sound field
characteristic. Execute correction data generation processing. First, in order to set the
measurement conditions, the control unit 1 displays the setting screen of the measurement band
number Mb, the measurement time Mt and the channel number Cn on the display unit 3 and
measures the number of measurement bands Mb via the operation unit 2 When the values of the
time Mt and the number of channels Cn are input, the input values are set as measurement
conditions (step S11). Here, the number of measurement bands Mb is the number of bands of the
band pass filter in the signal recording unit 7, and 31 bands are set in the present embodiment.
The measurement time Mt is a time for generating pink noise (measurement signal), and in the
present embodiment, 2 seconds is set. The number of channels Cn is the number of speakers
constituting the speaker group 20 to be corrected, and in the present embodiment, the total
number of front right speakers 21, center speakers 22, front left speakers 23 and 34, rear right
speakers 25 and rear left speakers 26 is calculated. Six units are set.
[0023]
Subsequently, the control unit 1 emits pink noise from the speaker group 20 to be measured
(step S12). Specifically, the control unit 1 controls the measurement signal generation unit 4 to
generate and output a pink noise audio signal, and after amplification by the power amplifier 5,
the speaker group 20 emits pink noise. In this configuration, pink noise is emitted in order from
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the speakers 21 to 26 constituting the speaker group 20 to be corrected, and the measurement
processing described later is performed. This processing is common to the speakers 21 to 26.
The case where pink noise is emitted from the front right speaker 21 will be described in detail
as an example.
[0024]
When the pink noise is emitted from the front right speaker 21, the pink noise is propagated in
the vehicle cabin, collected by the microphone 30, amplified by the microphone amplifier 6, and
input to the signal recording unit 7. The signal recording unit 7 performs an averaging process
on the input pink noise audio signal by band pass filtering for the measurement time Mt (2
seconds) set in step S1 to obtain a signal level for each 1/3 octave band. Then, the signal is
stored in the RAM of the control unit 1, and the control unit 1 reads out the signal level of each
1/3 octave band stored in the RAM and displays it on the display unit 3 (step S13).
[0025]
In this way, when the signal level for each 1/3 octave band is acquired from the front right
speaker 21, the control unit 1 controls the center speaker 22, the front left speaker 23, the
subwoofer 24, the rear right speaker 25, and the rear left speaker 26. The same processes as in
steps S2 to S3 are performed in the order of. When the control unit 1 performs the above
process for the number of channels Cn (6 channels in the present embodiment) (step S14: Yes),
the control unit 1 ends the sound field measurement process.
[0026]
FIG. 7 is a flowchart showing sound field correction data generation processing. When the sound
field measurement process is completed, the control unit 1 sets the reference bandwidth Sw, the
correction band range Ca, the number of PEQ bands En, the reference detection threshold St, and
the number of correction channels Cc to set the sound field correction conditions. Is displayed on
the display unit 3, and the operator inputs values of the reference bandwidth Sw, the correction
band range Ca, the PEQ band number En, the reference detection threshold St, and the correction
channel number Cc via the operation unit 2. Thereby, when the values of reference bandwidth
Sw, correction band range Ca, PEQ band number En (= five bands in the following description),
reference detection threshold St and correction channel number Cc are input, the input values
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are The field correction condition is set (step S21).
[0027]
Here, the reference bandwidth Sw is a bandwidth for calculating the signal level to be a reference
in the calculation unit 8, and in the present embodiment, 1 kHz to 5 kHz is set. The correction
band range Ca is a band range for correcting the frequency, and is set for each of the speakers
21 to 26 based on the reproducible frequency of the speaker group 20 and the like. In addition,
the PEQ band number En is the maximum number of peaking equalizers assigned to each of the
speakers 21 to 26, and is five in the present embodiment. The reference detection threshold St is
a threshold of the signal level for grouping the frequency adjustment band of the parametric
equalizer, and the correction channel number Cc is the number of the speakers 21 to 26
constituting the speaker group 20 to be corrected, that is, this embodiment There are six in form.
[0028]
Subsequently, the control unit 1 reads out the signal level of each band within the correction
band range Ca stored in the RAM (step S22), the calculation of the reference band signal level by
the calculation unit 8 and the normalized band signal level Y ( n) is calculated (step S23). In this
case, the calculation unit 8 obtains the average value of the signal level of each band within the
reference bandwidth Sw (1 kHz to 5 kHz). Then, the average value of the signal level for each
band is used as a reference band signal level, and the signal level for each band is converted so
that the reference band signal level is set to zero level (0 dB). Get (n). Here, n = 0, 1, 2,..., And Y
(0) is a normalized band signal level before correction.
[0029]
Next, the control unit 1 generates level correction data by inverting the sign of the normalized
band signal level Y (n) for each band by the calculation unit 8, and arranges the level correction
data for each band in frequency order. Based on the correction data waveform (correction level
waveform), grouping processing on the positive side of level correction data in the correction
band range Ca set in step S21 is executed (step S24), and level correction in the correction band
range Ca The grouping processing on the negative side of the data is executed (step S25).
[0030]
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More specifically, as grouping processing on the positive side of the level correction data
waveform, the control unit 1 sets a positive threshold level (for example, 1 dB (decibel)) by the
calculation unit 8 based on the reference detection threshold set in step S21. At the same time,
the positive side inflection point whose increment changes from negative to positive is detected
based on the positive side level correction data waveform, and the positive side level correction
data is grouped based on the positive threshold level and the positive side inflection point.
In this case, among the level correction data waveforms on the positive side, an area below the
positive threshold level (that is, an area where the absolute value of the level correction data
waveform is below the threshold) is excluded from the group to reduce the amount of
calculation. There is.
[0031]
Further, as grouping processing on the negative side of the level correction data waveform, the
control unit 1 sets the negative threshold level (for example, −1 dB (decibel)) by the calculation
unit 8 based on the reference detection threshold set in step S21. The negative side inflection
point whose increment changes from positive to negative is detected based on the negative side
level correction data waveform, and the negative side level correction data is grouped based on
the negative threshold level and the negative side inflection point. Also in this case, among the
level correction data waveforms on the negative side, the area above the negative threshold level
(that is, the area where the absolute value of the level correction data waveform is below the
threshold) is excluded from the group to reduce the calculation amount. ing. Then, for each
group, the control unit 1 determines whether the group number, the band number, the total
number of bands corresponding to the bandwidth of the level correction data included in the
group, and the level correction data included in the group are positive. A type (D) indicating
whether it is the negative side is associated and stored in a RAM (not shown).
[0032]
When grouping is completed, the control unit 1 causes the calculation unit 8 to add the level
values of the level correction data in the group for each group (step S26), and the group with the
largest added value is the correction target of the peaking equalizer. The correction group to be
selected is selected (step S27). When the correction group is selected, the control unit 1 causes
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the calculation unit 8 to calculate the barycentric position in the group using the band value and
level value of each level correction data in the correction group, and the band value of the
barycentric position in the group and The center frequency of the peaking equalizer
corresponding to the position of the center of gravity in the group is calculated based on the
level value (step S28), and the gain of the peaking equalizer corresponding to the position of the
center of gravity in the group is calculated (step S29). Further, the control unit 1 calculates the
frequency bandwidth of the peaking equalizer from the value weighted by the gain of the
peaking equalizer corresponding to the barycentric position in the group calculated by the
calculation unit 8 and the total number of bands in the correction group (step S30) . In this case,
the calculated frequency bandwidth narrows as the gain increases, and increases as the total
number of bands increases.
[0033]
When the center frequency, gain and frequency bandwidth of the peaking equalizer are
calculated by the processing in steps S28 to S10, the control unit 1 causes the display unit 3 to
display the center frequency, gain and frequency bandwidth and makes them sound The field
correction data is stored in the RAM as PEQ parameters constituting the data (step S31).
[0034]
Subsequently, the control unit 1 determines whether or not the calculation and storage of PEQ
parameters as many as the number of PEQ bands En set in step S21 are completed (step S32).
If it is determined in step S32 that calculation and storage of PEQ parameters equal in number to
the number of PEQ bands En set in step S21 have not been completed (step S32; No), the
calculated PEQ parameter is the signal correction level. The PEQ filter characteristic band signal
level Z (n) is calculated (step S33). Then, the control unit 1 adds the calculated PEQ filter
characteristic band signal level Z (n) to the current normalized band signal level Y (n) to obtain
the next PEQ filter characteristic band signal level Z (n + 1). The normalized band signal level Y
(n + 1) to be used in the calculation is calculated (step S34), and the process returns to step S24.
[0035]
FIG. 8 is an explanatory diagram of an example of the normalized band signal level Y (0) before
the signal level correction from the sound collected by the microphone. FIG. 9 is an explanatory
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diagram of the PEQ filter characteristic band signal level Z (1) obtained in the n = 1st process.
More specifically, since the process of step S24 to step S33 is the first process (n = 1) this time,
normalized band signal level Y (0) before signal level correction from the sound collected by the
microphone and The normalized band signal level Y (0 + 1) to be used in calculating the next
PEQ filter characteristic band signal level Z (1 + 1) is calculated using the current PEQ filter
characteristic band signal level Z (1) (step S34). In other words, it is as follows.
Y(1)=Y(0)+Z(1)
[0036]
FIG. 10 is an explanatory diagram of the normalized band signal level Y (1) used in the n = 2nd
process. That is, as shown in FIG. 10, the normalized band signal level Y (1) used in the n = 2nd
processing is the current PEQ to the normalized band signal level Y (0) before the signal level
correction of FIG. The filter characteristic band signal level Z (1) is added (effectively subtracted).
FIG. 11 is an explanatory diagram of the PEQ filter characteristic band signal level Z (2) obtained
in the n = 2th process. More specifically, since the processing of step S24 to step S33 is the
second processing (n = 2), the normalized band signal level Y (1) obtained last time and the PEQ
filter characteristic band signal of this time are obtained. The normalized band signal level Y (2)
used when calculating the next PEQ filter characteristic band signal level Z (2 + 1) is calculated
using the level Z (2) (step S34). In other words, it is as follows. Y(2)=Y(1)+Z(2)
[0037]
FIG. 12 is an explanatory diagram of the normalized band signal level Y (2) used in the n = 3th
process. That is, as shown in FIG. 12, the normalized band signal level Y (2) used in the n = 3th
process is equal to the normalized band signal level Y (1) of FIG. It becomes what added Z (2).
FIG. 13 is an explanatory diagram of the PEQ filter characteristic band signal level Z (3) obtained
in the n = 3th process. More specifically, since the process of step S24 to step S33 is the third
process (n = 3), the normalized band signal level Y (2) obtained last time and the PEQ filter
characteristic band signal of this time are obtained. The normalized band signal level Y (3) used
when calculating the next PEQ filter characteristic band signal level Z (3 + 1) is calculated using
the level Z (3) (step S34). In other words, it is as follows. Y(3)=Y(2)+Z(3)
[0038]
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FIG. 14 is an explanatory diagram of the normalized band signal level Y (3) used in the n = 4th
process. That is, as shown in FIG. 14, the normalized band signal level Y (3) used in the n = 4th
process is the current PEQ shown in FIG. 13 in the normalized band signal level Y (2) of FIG. The
filter characteristic band signal level Z (3) is added. FIG. 15 is an explanatory diagram of the PEQ
filter characteristic band signal level Z (4) obtained in the n = 4th process. More specifically, the
processing in step S24 to step S33 is the fourth processing this time (n = 4), so the previously
obtained normalized band signal level Y (3) and the current PEQ filter characteristic band signal
The normalized band signal level Y (4) used when calculating the next PEQ filter characteristic
band signal level Z (4 + 1) is calculated using the level Z (4) (step S34). In other words, it is as
follows. Y(4)=Y(3)+Z(4)
[0039]
FIG. 16 is an explanatory diagram of the normalized band signal level Y (4) used in the n = 4th
process. That is, as shown in FIG. 16, the normalized band signal level Y (4) used in the n = 4th
process is the current PEQ shown in FIG. 15 in the normalized band signal level Y (3) of FIG. The
filter characteristic band signal level Z (4) is added. When it is determined in step S32 that the
calculation and storage of PEQ parameters equal in number to the PEQ band number En set in
step S21 are completed (step S32; Yes), the speaker group 20 is configured. It is determined
whether calculation and storage of PEQ parameters corresponding to the speakers 22 to 26 are
all finished (step S35).
[0040]
If it is determined in step S35 that the calculation and storage of all PEQ parameters
corresponding to the other speakers 22 to 26 constituting the speaker group 20 have not been
completed yet, the process proceeds to step S22 again, and the speaker group Calculation and
storage of PEQ parameters corresponding to the other speakers 22 to 26 constituting 20 are
performed (steps S22 to S34). On the other hand, when the calculation and storage of the PEQ
parameter corresponding to each of the center speaker 22, the front left speaker 23, the
subwoofer 24, the rear right speaker 25 and the rear left speaker 26 end in the determination of
step S35 (step S35: Yes) The sound field correction data generation process ends.
[0041]
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FIG. 17 is an explanatory diagram of the combined characteristic of the filter characteristic of the
present embodiment. As shown in FIG. 17, the combined characteristics of the filter
characteristics obtained according to this embodiment can be corrected also for the dipping
around 80 Hz, compared to the combined characteristics of the filter characteristics shown in
FIG. It can be seen that precise correction close to the characteristics of the target can be
performed. Therefore, when the CD or DVD is reproduced by the recording medium reproducing
unit 10, the audio signal is corrected to a desired characteristic by each parametric equalizer by
setting the PEQ parameter constituting the data for audio correction to each parametric
equalizer. The corresponding sound can be emitted from the speaker group 20.
[0042]
As described above, according to the present embodiment, each time the PEQ parameter for one
band is obtained, the characteristic is added to the normalized band signal level Y (n) to be
corrected. The PEQ parameters are calculated taking into account the correction effect of the
PEQ band of This makes it possible to perform precise correction closer to the characteristics of
the target. Further, according to the present embodiment, pink noise emitted from the speaker
group 20 is collected by the microphone 30, and level correction data (signal correction level) for
each frequency band is determined from the collected sound, and these levels are obtained. Since
the frequency band is divided into groups based on the inflection point of the level correction
data waveform in which the correction data are connected in order of frequency and the
predetermined threshold, the peaks and valleys present in the level correction data waveform for
each peak and every valley It is possible to reduce the amount of calculation by excluding the
region where the absolute value of the level correction data waveform is equal to or less than the
threshold from the grouping.
[0043]
Furthermore, in the present embodiment, since the parametric equalizer is set in group units,
correction characteristics substantially the same as the level correction data waveform can be
obtained even with the use of a small number of peaking equalizers. It can be corrected
accurately. In addition, the barycentric position is determined using the band value and level
value of the level correction data waveform in the group, and the center frequency and gain of
the parametric equalizer are set based on the band value and level value of the barycentric
position, and the level in the group Since the frequency bandwidth of the peaking equalizer
constituting the parametric equalizer is set from the total number of bands of the correction data
waveform, that is, the combination of the frequency bandwidth and the gain, the peaks or valleys
08-05-2019
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of the level correction data waveform divided into groups It is possible to obtain a correction
characteristic of a parametric equalizer that substantially matches the curve of. Moreover,
although the case where pink noise was used as a predetermined | prescribed measurement
signal was shown in the above description, not only this but the measurement signal which can
measure sound fields, such as white noise, can be applied widely.
[0044]
FIG. 18 is a flowchart showing sound field correction data generation processing of the
modification. In the above description, the PEQ filter characteristic band signal level Z (n) which
is the signal correction level is calculated from the PEQ parameter calculated for each band (step
S33), and the calculated PEQ filter characteristic band signal level Z (n) is calculated. By adding
to the current normalized band signal level Y (n), the normalized band signal level Y (n + 1) to be
used when calculating the next PEQ filter characteristic band signal level Z (n + 1) is calculated
(step S34) However, as shown in FIG. 18, the PEQ parameter is calculated for M bands by
repeating the processes of steps S28 to S31, step S36, and step S37 M times, and the PEQ for M
bands is calculated. Calculate the PEQ filter characteristic band signal level Z (n) which is the
signal correction level from the parameters ( Step S38) When calculating the next PEQ filter
characteristic band signal level Z (n + 1) by adding the calculated PEQ filter characteristic band
signal level Z (n) to the current normalized band signal level Y (n) It is also possible to configure
so as to calculate the normalized band signal level Y (n + 1) used for (step S34).
[0045]
Further, in the above description, the case is described in which the level characteristic of the
audio signal for each frequency band is corrected to be flat. In the above description, the band
pass filter is used to calculate the signal level for each reference bandwidth. However, the present
invention is not limited to this. FFT (Fast Fourie Transform) processing is performed on the audio
signal collected by the microphone 30 , And may perform the same calculation as the band pass
filter in the frequency domain to calculate the signal level for each reference bandwidth.
Although the above embodiment shows the case where the present invention is applied to a
vehicle-mounted sound field correction apparatus, the present invention is not limited to this, and
any sound field such as a sound field correction apparatus built in an audio amplifier used in a
house It can be widely applied to the correction device.
[0046]
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17
In the above description, the case where the control program for realizing each of the functions
is stored in advance in the ROM has been described, but the control program may be recorded on
a computer readable recording medium. With such a configuration, when the computer reads the
program from the storage medium and executes the process according to the read program, the
same operation and effect as the image information processing apparatus of the above
embodiment can be obtained. Here, the storage medium is a semiconductor storage medium such
as RAM or ROM, a magnetic storage type storage medium such as FD or HD, an optical reading
type storage medium such as CD, CDV, LD or DVD, or a magnetic storage type such as MO. The
optical storage medium may be any computer readable storage medium regardless of the reading
method such as electronic, magnetic, optical, etc. . It is also possible to configure to download,
install and execute the control program via a communication network such as the Internet or
LAN.
[0047]
It is a block diagram showing functional composition of a sound field amendment device. It is a
figure which shows arrangement | positioning of the speaker in a vehicle. It is explanatory
drawing of an example of acoustic characteristic measurement data. It is explanatory drawing of
an example of a filter characteristic. It is explanatory drawing of the synthetic | combination
characteristic of the filter characteristic of FIG. It is a flow chart which shows sound field
measurement processing of an embodiment. It is a flow chart which shows data generation
processing for sound field amendment. It is explanatory drawing of an example of the
normalization band signal level Y (0) before signal level correction | amendment from the audio |
voice collected by the microphone. It is explanatory drawing of PEQ filter characteristic band
signal level Z (1) obtained by the process of n = 1st time. It is explanatory drawing of
normalization band signal level Y (1) used by the process of n = 2nd time. It is explanatory
drawing of PEQ filter characteristic band signal level Z (2) obtained by the process of n = 2nd
time. It is explanatory drawing of normalization band signal level Y (2) used by the process of n =
3rd time. It is explanatory drawing of PEQ filter characteristic band signal level Z (3) obtained by
the process of n = 3rd time. It is explanatory drawing of normalization band signal level Y (3)
used by the process of n = 4th. It is explanatory drawing of PEQ filter characteristic band signal
level Z (4) obtained by the process of the n = 4th time. It is explanatory drawing of normalization
band signal level Y (4) used by the process of the n = 4th time. It is explanatory drawing of the
synthetic | combination characteristic of the filter characteristic of this embodiment. It is a flow
chart which shows data generation processing for sound field amendment of a modification.
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Explanation of sign
[0048]
Reference Signs List 1 control unit 2 operation unit 3 display unit 4 measurement signal
generation unit 5 power amplifier 6 microphone amplifier 7 signal recording unit 8 calculation
unit 9 parametric equalizer (PMEQ) 10 recording medium reproduction unit 11 D / A converter
12 A / D converter 20 speaker Group 30 Microphone 40 Vehicle 100 Sound Field Correction
Device Y (n) Normalized Band Signal Level Z (n) PEQ Filter Characteristic Band Signal Level
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