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JP2007189317

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DESCRIPTION JP2007189317
A sound field correction apparatus capable of correcting frequency characteristics to target
characteristics with high accuracy and a control method thereof are provided. SOLUTION: A pink
noise emitted from a speaker is collected by a microphone, level correction data for each
frequency band is obtained from the collected sound, and a level correction data waveform α
obtained by connecting these level correction data in order of frequency The frequency bands
are grouped based on the inflection point (“23, 26”) of and the positive and negative
thresholds, and parametric equalizers are set in group units. [Selected figure] Figure 6
Sound field correction apparatus and control method thereof
[0001]
The present invention relates to a sound field correction apparatus and 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
1).
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[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]
The present invention has been made in view of the above-described circumstances, and it is an
object of the present invention to provide a sound field correction apparatus and control method
thereof capable of accurately correcting level characteristics for each frequency band to target
characteristics. .
[0007]
The present invention relates to a sound field correction apparatus for collecting a sound emitted
from a speaker with a microphone and performing level correction for each frequency band of a
sound signal output to the speaker based on the collected sound. A plurality of parametric
equalizers capable of level adjustment for each frequency band and signal correction levels for
each frequency band from the sound collected by the microphone, and an inflection point of a
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correction level waveform in which the signal correction levels are connected in frequency order
The frequency bands are divided into groups on the basis of, and setting means for setting each
of the parametric equalizers to perform level correction on a group basis is provided.
[0008]
In this case, the setting means may divide the frequency band into groups based on the inflection
point of the correction level waveform and a predetermined threshold level.
The setting means may determine a barycentric position of the correction level waveform in the
group, and set a center frequency and a gain of the parametric equalizer based on a frequency
and a signal level of the barycentric position.
The setting means may set 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. .
[0009]
According to a control method of a sound field correction device for collecting a sound emitted
from a speaker by a microphone and performing level correction for each frequency band of an
audio signal to be output to the speaker based on the collected sound, the collection by the
microphone The signal correction level for each frequency band is determined from the sounded
voice, and the frequency bands are divided into groups based on the inflection point of the
correction level waveform in which the signal correction levels are connected in frequency band
order, and level correction is performed in units of this group. Preferably, a plurality of
parametric equalizers capable of level adjustment according to frequency bands of the audio
signal are respectively set.
[0010]
According to the present invention, the frequency characteristic can be corrected to the target
characteristic with high accuracy.
[0011]
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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 adjusts the signal level for each frequency band of the
audio signal output to the plurality of speakers 20 disposed in the vehicle compartment.
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 PEQ
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.
[0012]
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.
[0013]
The measurement signal generator 4 outputs a pink noise digital audio signal (measurement
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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 dudes processing, and outputs digital signals of audio and video to the
parametric equalizer unit. (Hereafter, it is called PEQ9. Output to).
[0014]
PEQ 9 is a parametric equalizer having an IIR filter and capable of adjusting the center
frequency, gain, and frequency bandwidth, and level adjustment of the digital audio signal output
from measurement signal generating unit 4 or recording medium reproducing unit 10 by
frequency band I do. The PEQ 9 in this embodiment is provided with 32 parametric equalizers
that can handle 32 bands. The D / A (Digital / Analog) converter 11 converts the digital audio
signal that has passed through the PEQ 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 20. The
power amplifier 5 in the present embodiment is a multichannel power amplifier corresponding to
a plurality of channels.
[0015]
The microphone amplifier 6 amplifies an analog audio signal output from the microphone 30
connected to the sound field correction apparatus 100 and outputs the signal to the A / D
converter 12. The measurement signal generator 4 emits sound from the speaker 20. The pink
noise audio signal is input from the microphone 30, and the input pink noise audio signal 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 processes 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 PEQ 9 Output to
control unit 1.
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[0016]
The speaker 20 in the present embodiment is, as shown in FIG. 2, a front right speaker 21
disposed on the front right side of the driver's seat 41 of the vehicle 40, and a center disposed on
the front between the driver's seat 41 and the passenger seat 42. The speaker 22, the front left
speaker 23 disposed on the front left side of the passenger seat 42, the subwoofer 24 disposed
on the rear center of the rear seat 43, the rear right speaker 25 disposed on the rear right of the
rear seat 43, and the rear seat 43 It comprises the rear left speaker 26 disposed on the rear left
side. The microphone 30 is disposed at the listening position and collects pink noise emitted
from the speaker 20. In the present embodiment, the microphone 30 is disposed at the center of
the driver's seat 41, the assistant seat 42, and the rear seat 43. ing. 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.
[0017]
Next, the operation of the sound field correction apparatus 100 will be described. 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. FIG. 3 is a flowchart showing the
sound field measurement process. 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 channel number Cn
are input, this input value is set as the measurement condition (step Sa1). Here, the number of
measurement bands Mb is the number of bands of the band pass filter in the signal recording
unit 7. In the present embodiment, 31 bands are set, and the measurement time Mt is a time for
generating pink noise (measurement signal). In the embodiment, 2 seconds are set. The number
of channels Cn is the number of speakers 20 to be corrected, and in the present embodiment, six
front right speakers 21, center speakers 22, front left speakers 23 and 34, rear right speakers 25
and rear left speakers 26 are set. .
[0018]
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Subsequently, the control unit 1 causes the speaker 20 to be measured to emit pink noise (step
Sa2). Specifically, the control unit 1 controls the measurement signal generation unit 4 to output
an audio signal of pink noise, and after amplifying by the power amplifier 5, the speaker 20
emits pink noise. In this configuration, pink noise is emitted sequentially from the plurality of
speakers 20 to be corrected and measurement processing described later is performed. However,
since this processing is common to each speaker 20, pink noise is output from the front right
speaker 21 below. The details of the case where the noise is emitted will be described.
[0019]
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 the band pass filter process for the measurement time Mt
(2 seconds) set in step S1, and acquires a signal level for each band to obtain a control unit. The
signal is stored in the RAM 1 and the control unit 1 reads out the signal level of each band stored
in the RAM and displays it on the display unit 3 (step Sa3).
[0020]
In this way, when the signal level for each band from the front right speaker 21 is acquired, 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 in this order. If the same processing as steps
S2 to S3 is performed and the above processing is performed the number of channels Cn (for
example, six channels in this embodiment) (step Sa4: Yes), the sound field measurement
processing is ended.
[0021]
FIG. 4 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
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conditions. When the values of reference bandwidth Sw, correction band range Ca, number of
PEQ bands En, reference detection threshold St and number of correction channels Cc are input
through operation unit 2, these input values are input. The sound field correction conditions are
set (step Sb1).
[0022]
Here, the reference bandwidth Sw is a bandwidth for calculating the signal level to be a reference
in the calculation unit 8. In the present embodiment, 1 kHz to 5 kHz is set, and the correction
band range Ca is a band range for correcting the frequency. And the band range set for each
speaker 20 based on the reproducible frequency of the speaker 20 and the like. The number of
PEQ bands En is the number of parametric equalizers used for one speaker 20, and is set to six in
the present embodiment. As described above, since the PEQ 9 has a total of 32 parametric
equalizers, the control unit 1 includes six front right speakers 21, center speakers 22, front left
speakers 23, rear right speakers 25 and rear left speakers 26. Assign each of the parametric
equalizers, and assign the remaining two parametric equalizers to the subwoofer 24. The
reference detection threshold St is a threshold of the signal level for grouping the frequency
adjustment band of the parametric equalizer, and the number of correction channels Cc is the
number of speakers 20 to be corrected.
[0023]
Subsequently, the control unit 1 reads out the signal level of each band within the correction
band range Ca stored in the RAM (step Sb2), and the calculation unit 8 calculates the reference
band signal level and calculates the normalized band signal level. And (step Sb3). In this case, the
calculation unit 8 obtains an average value of signal levels for each band within the reference
bandwidth Sw (1 kHz to 5 kHz), and uses this as a reference band signal level, and as shown in
FIG. The signal level of each band is converted so as to be zero level to obtain a normalized band
signal level of each band.
[0024]
Next, the control unit 1 generates level correction data in which the sign of the normalized band
signal level for each band is inverted by the calculation unit 8 (step Sb4), and as shown in FIG.
The positive side grouping process of the level correction data within the correction band range
Ca set in step Sb1 is executed based on the level correction data waveform (correction level
waveform) α in which the frequency bands are arranged in order of frequency (step Sb5) The
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grouping processing on the negative side of the level correction data within the correction band
range Ca is executed (step Sb6).
[0025]
More specifically, as grouping processing on the positive side of the level correction data
waveform, as shown in FIG. 6, the control unit 1 sets a positive threshold level (for example, 1
dB) based on the reference detection threshold set by the calculation unit 8 in step Sb1. While
setting (decibel) and detecting the positive side inflection point (band number (B) in FIG. 6 is
“23, 26”), the increment changes from negative to positive based on the level correction data
waveform on the positive side. Group the level correction data on the positive side on the basis of
the 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. Thus, as shown in FIG. 7, the band number (B) in FIG. 6 assigns the portion
“7” to the group number G1, and the band number (B) in FIG. 6 places the portions “21, 22”
in the group number. The band number (B) in FIG. 6 assigns the portion "24, 25" to the group
number G3 and the band number (B) in FIG. 6 assigns the portion "27, 28, 29, 30" to the group
number. It can be assigned to G4.
[0026]
Further, as grouping processing on the negative side of the level correction data waveform, as
shown in FIG. 6, the control unit 1 sets the negative threshold level (for example, −1 dB (eg, −1
dB) based on the reference detection threshold set by the calculation unit 8 in step Sb1. The
negative threshold value and negative side inflection point are detected by setting the negative
side inflection point (with no inflection point in FIG. 6) in which the increment changes from
positive to negative based on the negative side level correction data waveform. And group the
negative level correction data into groups. 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. Thus, as shown in FIG. 7, the
band number (B) in FIG. 6 assigns the portion “9, 10” to the group number G5, and the band
number (B) in FIG. G6 can be assigned, and the band number (B) in FIG. 6 can assign the portion
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of "15, 16, 17, 18, 19" to the group number G7. In this case, as shown in FIG. 7, the control unit
1 sets “band number (A)”, “band number (B)”, and a bandwidth of level correction data
included in the group for each group. The corresponding "total number of bands (C)" and "type
(D)" indicating whether the level correction data included in the group is on the positive side or
the negative side are associated with each other and stored in the RAM.
[0027]
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 Sb7), and the group with the
largest addition value is the correction target of the parametric equalizer The correction group to
be selected is selected (step Sb8). When the correction group is selected, the control unit 1
causes the calculation unit 8 to calculate the position of the center of gravity using the band
value and the level value of each level correction data in the correction group, and based on the
band value and the level value of the center of gravity position. The central frequency and gain of
one parametric equalizer are calculated (steps Sb9, Sb10). Further, the control unit 1 calculates
the frequency bandwidth of the parametric equalizer from the value weighted by the gain and
the “total number of bands (C) in the correction group” by the calculation unit 8 (step Sb11).
In this case, the calculated frequency bandwidth narrows as the gain increases, and increases as
the total number of bands (C) increases.
[0028]
When the center frequency, gain and frequency bandwidth of one parametric equalizer are
calculated by the processing of steps Sb9 to Sb11, the control unit 1 causes the display unit 3 to
display the center frequency, gain and frequency bandwidth and Are stored in the RAM as PEQ
parameters constituting sound field correction data (step Sb12).
[0029]
Subsequently, the control unit 1 determines whether calculation and storage of PEQ parameters
equal in number to the PEQ band number En set in step Sb1 are completed (step Sb13), and if
not completed (step Sb13: No) The group having the next largest added value among the added
values for each group calculated in step Sb7 is selected as the correction group (step Sb14), and
the processing in steps Sb9 to Sb13 described above is repeated.
[0030]
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In the present embodiment, since the number of PEQ bands En corresponding to the front right
speaker 21 is 6, the group number G4, in order of increasing level addition value of the level
correction data, from among the groups G1 to G7 to be correction candidates. Six groups of
group number G7, group number G3, group number G1, group number G2 and group G5 are set
as correction groups, and six PEQ parameters are calculated.
Then, as shown in FIG. 8, the PEQ characteristic P4 for correcting the frequency band level of the
group number G4 and the correction characteristic for correcting the frequency band level of the
group number G7 by setting each PEQ parameter to the parametric equalizer respectively A
correction characteristic P3 for correcting the frequency band level of the group number G3, a
correction characteristic P1 for correcting the frequency band level of the group number G1, and
a correction characteristic P2 for correcting the frequency band level of the group number G2
can be set.
For this reason, as shown in FIG. 9, a level correction data waveform corresponding to an ideal
characteristic that flattens the level characteristic of each frequency band of the audio signal as
the combined correction characteristic β obtained by combining these correction characteristics
P1 to P5 and P7 It can be approximately the same as α.
[0031]
When control unit 1 determines in step Sb13 that the calculation and storage of PEQ parameters
as many as the number of PEQ bands En have been completed, it performs calculation and
storage of PEQ parameters corresponding to other speakers 20 (step Sb2). When calculation and
storage of PEQ parameters corresponding to each of center speaker 22, front left speaker 23,
subwoofer 24, rear right speaker 25 and rear left speaker 26 are completed (step Sb15: Yes), for
sound field correction End the data generation process. 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 20.
[0032]
According to the present embodiment, pink noise emitted from the speaker 20 is collected by the
microphone 30, level correction data (signal correction level) for each frequency band is
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determined from the collected sound, and these level correction data are calculated. The
frequency bands are grouped based on the inflection point of the level correction data waveform
α connected in the order of frequency and the predetermined threshold, so the peaks and
valleys present in the level correction data waveform α for each peak and every valley While
grouping can be performed, an area where the absolute value of the level correction data
waveform is equal to or less than the threshold can be excluded from grouping to reduce the
amount of calculation.
[0033]
Then, in the present embodiment, since the parametric equalizer is set in group units, the
correction characteristic β substantially the same as the level correction data waveform α can
be obtained even with the use of a small number (six) of parametric equalizers. The level
characteristics can be accurately corrected to the target characteristics.
In addition, the barycentric position is determined using the band value and level value of the
level correction data waveform α 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.
Since the frequency bandwidth of the parametric equalizer is set based on the “total number of
bands (C)” of the level correction data waveform α, that is, the combination of the frequency
bandwidth and the gain, the peaks or valleys of the level correction data waveform grouped It is
possible to obtain a correction characteristic of a parametric equalizer that substantially matches
the curve of.
[0034]
As mentioned above, although the present invention was explained based on one embodiment,
the present invention is not limited to this. For example, although the case where pink noise is
used as a measurement signal is shown in the above embodiment, the present invention is not
limited to this, and a measurement signal capable of measuring a sound field such as white noise
can be widely applied.
[0035]
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In the embodiment described above, the level characteristic of the audio signal in each frequency
band is corrected to be flat. However, the present invention is not limited to this and the
characteristic may be corrected to any characteristic. Although in the above embodiment, a band
pass filter is used to calculate the signal level for each reference bandwidth, the present invention
is not limited to this, and FFT (Fast Fourier Transform) processing is performed on the audio
signal collected by the microphone 30. The signal level for each reference bandwidth may be
calculated by performing the same calculation as the band pass filter in the frequency domain.
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.
[0036]
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 a flowchart which
shows a sound field measurement process. It is a flow chart which shows data generation
processing for sound field amendment. It is a figure which shows the normalization band signal
level of the recorded audio | voice. It is a figure which shows level correction data. It is a figure
which shows the result of grouping. It is a figure which shows the correction | amendment
characteristic of the parametric equalizer for every group. It is a figure which shows the synthetic
| combination correction characteristic by several parametric equalizer, and a level correction
data waveform.
Explanation of sign
[0037]
DESCRIPTION OF SYMBOLS 1 control part (setting means) 4 measurement signal generation part
7 signal recording part 8 calculation part 9 parametric equalizer part 20 speaker 30 microphone
100 sound field correction apparatus
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