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JP2010181448

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DESCRIPTION JP2010181448
The present invention provides an acoustic adjustment device and an acoustic adjustment
method capable of correctly identifying the acoustic characteristics of a space using a colored
sound signal. A sound adjustment device for adjusting sound in a predetermined space, which
divides a sound source signal of colored sound reproduced by a speaker and a sound collection
signal collected by a microphone into a plurality of partial frequency bands Means, determining
means for determining whether the sound source signal is effective for estimation of the transfer
function based on the signal level of the sound source signal in the partial frequency band, the
sound source signal determined to be effective by the determining means Estimating means for
estimating a partial acoustic transfer function in a partial frequency band of the sound source
signal and the collected signal based on a collected signal, and synthesis for combining partial
acoustic transfer functions estimated by the estimating means for a plurality of partial frequency
bands It is set as the acoustic adjustment apparatus provided with the means. [Selected figure]
Figure 3
Acoustic adjustment device and acoustic adjustment method
[0001]
The present invention relates to an acoustic adjustment device and an acoustic adjustment
method.
[0002]
Conventionally, an acoustic transfer function between a speaker and a listener who listens to
music or the like emitted from the speaker in a predetermined space is estimated (identified), and
an adaptive filter in which filter coefficients are set based on the acoustic transfer function There
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is known a technique for improving the sense of realism of audio (for example, music etc.) heard
by a listener by outputting an audio signal from a speaker.
[0003]
As a method of identifying an acoustic transfer function, a predetermined signal generated for a
test (hereinafter, referred to as "white noise").
The method of using is generally used.
When the acoustic transfer function is identified by this method, a microphone is installed at a
position where the listener listens to music, and the microphone collects white noise emitted
from the speaker.
[0004]
FIG. 1 is an explanatory view of a conventional acoustic transfer function identification method.
As shown in FIG. 1A, white noise is a signal having a constant signal level from low frequency to
high frequency. Therefore, by collecting the white noise with a microphone and analyzing the
frequency characteristics and signal level of the resulting signal, as shown in FIG. 1 (b), the low
frequency to high frequency in the space between the speaker and the microphone The acoustic
characteristics desired to be obtained can be calculated uniformly, and the acoustic transfer
function can be identified based on the measurement result.
[0005]
As described above, white noise includes a wide frequency band from low frequency to high
frequency and thus is an effective signal for use in identifying an acoustic transfer function, but
since it is a noise, it is annoying for the listener. It is a good sound. Therefore, identification of the
acoustic frequency by white noise has been performed in advance when there is no listener or
before playing music or the like.
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[0006]
As described above, when identification of the acoustic transfer function is performed in advance,
then, if the temperature and humidity of the space change during the reproduction of music or
the like, and the positional relationship between the speaker and the listener changes, the space
between the speaker and the listener There is a possibility that the acoustic characteristic in
Therefore, it is desirable to identify the acoustic transfer function at any time, but as described
above, since white noise is a harsh sound to the listener, if identifying the acoustic transfer
function by white noise as needed during reproduction of music etc., There may be a problem of
impairing the listener's comfort.
[0007]
As a technique for solving such a problem, a technique for identifying the acoustic characteristic
of a space using a music signal output to a speaker during reproduction of music, not white
noise, has been devised (see, for example, Patent Document 1). ).
[0008]
JP, 2007-243242, A
[0009]
However, when a music signal is used as in the above-mentioned prior art, the acoustic
characteristics of the space may not be accurately measured, and there is a possibility that the
acoustic characteristics of the space can not be correctly identified.
[0010]
The music signal is a sound whose scale and strength of the sound change as the melody
progresses (hereinafter referred to as "colored sound").
Since the signal is converted into a signal, it often does not have a constant signal level in the
frequency band from low frequency to high frequency like white noise.
[0011]
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For example, as shown in FIG. 1C, the audio signal of colored sound at a certain time (t) is a band
with a relatively low frequency (hereinafter, referred to as a "low frequency band".
The signal level in) is sufficiently high and the frequency band is relatively high (hereinafter
referred to as "high frequency band").
Consider the case where the signal level in) is very low.
[0012]
In this case, assuming that the actual acoustic characteristic in a certain space is the acoustic
characteristic shown in FIG. 1 (b), the acoustic characteristic obtained by calculation is as shown
in FIG. 1 (d) for the low frequency band. Can reproduce the acoustic characteristics well because
the signal level of the music signal is sufficiently high, but the acoustic characteristics can be
reproduced well because the signal level of the music signal is very low in the high frequency
region It is not possible to reproduce an acoustic characteristic whose signal level is lower than
that of the actual acoustic characteristic (the alternate long and short dashed line in FIG. 1D).
[0013]
On the other hand, as shown in FIG. 1 (e), when the audio signal of colored sound at a certain
time (t + 1) has a very low signal level in the low frequency band and a sufficiently high signal
level in the high frequency band, As shown in FIG. 1 (f), in the high frequency band, since the
signal level of the music signal is sufficiently high, it is possible to reproduce the acoustic
characteristics well, but in the low frequency region, the signal level of the music signal Is very
low, so that the acoustic characteristics can not be reproduced well, and the acoustic
characteristics having a signal level lower than that of the actual acoustic characteristics (the
alternate long and short dash line in FIG. 1F) are reproduced.
[0014]
As described above, when an acoustic characteristic such as an acoustic transfer function in a
certain space is identified using a colored sound signal, the frequency characteristic of the
speech signal temporally changes, so the acoustic characteristic of the space is accurately
measured. In some cases, it may not be possible to correctly identify the acoustic characteristics
of the space.
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[0015]
Then, an object of this invention is to provide the acoustic control apparatus which can identify
the acoustic characteristic of space correctly using the audio signal of a colored sound, and the
acoustic control method.
[0016]
In the present invention, it is an acoustic adjustment device that adjusts the sound in a
predetermined space by estimating an acoustic transfer function between a speaker and a
microphone that collects sound reproduced by the speaker, and is reproduced by the speaker A
division means for dividing a source signal of colored sound into a plurality of partial frequency
bands and also dividing a collected sound signal collected by the microphone into the partial
frequency band; signal level of the source signal in the partial frequency band Determining
means for determining whether the sound source signal is effective for estimating the transfer
function based on the sound source signal and the sound collection signal determined to be
effective by the determining means; And estimation means for estimating a partial acoustic
transfer function representing the acoustic transfer function in the partial frequency band of the
sound collection signal; It was decided to provide an acoustic adjustment apparatus and a
combining means for combining said partial acoustic transfer function estimated by means for a
plurality of said partial frequency bands.
[0017]
According to the present invention, in the partial frequency band of the sound source signal
determined to be effective for transfer function estimation based on the sound source signal
determined to be effective and the sound collection signal in the same partial frequency band as
the sound source signal. In order to estimate partial acoustic transfer functions and synthesize
partial acoustic transfer functions estimated for each partial frequency band, when acoustic
characteristics such as acoustic transfer functions in a certain space are identified using speech
signals of colored sounds The acoustic characteristics of the space can be accurately measured,
and the acoustic characteristics of the space can be correctly identified.
[0018]
It is explanatory drawing of the identification method of the conventional sound transfer
function.
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It is an explanatory view showing an application example of a sound adjustment device
concerning this embodiment.
It is a functional block diagram showing the composition of the sound adjustment device
concerning this embodiment.
It is explanatory drawing of the identification method of the sound transfer function by the sound
adjustment apparatus which concerns on this embodiment.
It is explanatory drawing which shows the procedure by which each partial sound transfer
function is memorize | stored in a memory | storage part.
It is an explanatory view showing the detailed composition of the sound adjustment device
concerning this embodiment.
It is a flow chart which shows a flow of processing when CPU of DSP runs a sound adjustment
program.
[0019]
Hereinafter, an embodiment of a sound adjustment device and a sound adjustment method
according to the present invention will be specifically described with reference to the attached
drawings. FIG. 2 is an explanatory view showing an application example of the sound adjustment
device according to the present embodiment. As shown in FIG. 2, the sound adjustment apparatus
10 according to the present embodiment includes music, voice, radio, television, car navigation
system stored in a portable storage medium such as a CD (Compact Disc) or a DVD (Digital
Versatile Disc). , Etc. A voice or music signal input from the playback device 200 that outputs
music or voice, etc. Is output to the speaker 201 through an adaptive filter section 62 (see FIG. 6)
described later, thereby adjusting the sound in space and improving the realism of music etc. that
the listener 203 listens to.
[0020]
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Reference numeral 202 in FIG. 2 is a microphone installed near the listener 203 and collecting
colored sound such as music output from the speaker 201. The microphone 202 picks up the
collected colored sound as an audio signal (hereinafter referred to as a "sound collection signal").
) And output to the sound adjustment apparatus 10. Here, the colored sound is a sound whose
scale or strength of sound changes as the melody or the like progresses.
[0021]
In the sound adjustment device 10, the sound transfer function of the space between the speaker
201 and the listener 203 is estimated as needed based on the sound source signal input from the
reproduction device 200 and the sound collection signal input from the microphone 202. . Then,
the sound adjustment device 10 outputs the sound source signal to the speaker 201 through the
adaptive filter in which the filter coefficient calculated based on the estimated sound transfer
function is adjusted.
[0022]
Here, the configuration of the sound adjustment device 10 according to the present embodiment
will be described with reference to FIG. FIG. 3 is a functional block diagram showing the
configuration of the sound adjustment device 10. As shown in FIG. As illustrated in FIG. 3, the
division unit 20, the determination unit 30, the estimation unit 40, the storage unit 50, and the
combination unit 60 are provided.
[0023]
The dividing unit 20 divides the sound source signal of the colored sound reproduced by the
speaker 201 into a plurality of partial frequency bands, and the same partial frequency as the
partial frequency band of the sound source signal for the collected sound signal collected by the
microphone 202 It is a processing unit that functions as dividing means for dividing into bands.
[0024]
In the present embodiment, the dividing unit 20 sets a frequency band higher than the
intermediate frequency (hereinafter referred to as “high frequency band”) at an intermediate
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frequency in the audible range (range of frequencies audible to human beings). H. "
And a frequency band lower than the intermediate frequency (hereinafter referred to as "low
frequency band L"). ) Into two partial frequency bands and output to the determination unit 30.
[0025]
Further, the dividing unit 20 divides the collected signal input from the microphone 202 into two
partial frequencies, a high frequency band H whose frequency is higher than the intermediate
frequency and a low frequency band L whose frequency is lower than the intermediate
frequency, as the sound source signal. Divide into bands. The collected sound signal for each
partial frequency band obtained by dividing the collected sound signal is output to the estimation
unit 40, respectively.
[0026]
In the present embodiment, although the sound source signal and the sound collection signal are
divided into two partial frequency bands by the dividing unit 20, the number of partial frequency
bands to be divided is not limited to this, and any number may be used. It may be divided into
partial frequency bands. However, even when the sound source signal and the sound collection
signal are divided into three or more partial frequency regions, the sound source signal and the
sound collection signal are divided at the same frequency width.
[0027]
The determination unit 30 is a processing unit that determines whether or not the sound source
signal is effective for estimation of the acoustic transfer function based on the signal level of each
sound source signal in each partial frequency band input from the dividing unit 20. . When the
sound source signal of each of the high frequency band H and the low frequency band L is equal
to or higher than a predetermined signal level, the determination unit 30 determines that the
sound source signal is effective for estimation of the acoustic transfer function and estimates
Output to 40
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[0028]
That is, the determination unit 30 includes a predetermined threshold as a reference for
determining whether the sound source signal of each partial frequency band input from the
division unit 20 is effective or invalid for estimation of the acoustic transfer function. As the
threshold set here, for example, the value of the signal level of white noise is used. Then, when
the signal level of the sound source signal is equal to or higher than this threshold value, it is
determined that the sound source signal is effective for estimation of the acoustic transfer
function. Further, when the signal level of the sound source signal does not reach the
predetermined signal level, the determination unit 30 discards the sound source signal without
outputting it to the estimation unit 40.
[0029]
For example, when a sound source signal as shown in FIG. 4 (a) is input to the dividing unit 20 at
a certain time (t), the sound source signal shown in the region on the left of the dashed dotted
line shown in the center of FIG. Is input to the determination unit 30 as a sound source signal in
the low frequency band L, and a sound source signal shown in the region on the right side of the
alternate long and short dash line shown in the center of FIG. Ru.
[0030]
In this case, since the signal level of the sound source signal in the low frequency band L at time
(t) is equal to or higher than the threshold value, the determination unit 30 determines that the
sound transfer function is effective and the sound source signal is sent to the estimation unit 40
in the subsequent stage. Output.
On the other hand, the determination unit 30 determines that the signal level of the audio signal
in the high frequency band H at time (t) is less than the threshold and determines that it is
invalid, and discards the sound source signal without outputting it to the estimation unit 40 in
the subsequent stage.
[0031]
Thereafter, at time (t + 1), when the sound source signal as shown in FIG. 4C is input to the
dividing unit 20, the sound source shown in the region on the left side of the dashed dotted line
shown in the center of FIG. The signal is input to the determination unit 30 as a sound source
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signal in the low frequency band L, and the sound source signal shown in the region on the right
of the alternate long and short dashed line shown in the center of FIG. Be done.
[0032]
In this case, the determination unit 30 determines that the signal level of the sound source signal
in the low frequency band L at time (t + 1) is less than the threshold value and determines that
the sound source signal is invalid. Destroy
On the other hand, since the signal level of the sound source signal in the high frequency band H
at time (t + 1) is equal to or higher than the threshold, the determination unit 30 determines that
the sound transfer function is effective for estimation. Output.
[0033]
In the present embodiment, although the determination unit 40 determines that the sound
source signal whose signal level is equal to or higher than the predetermined signal level is
effective for estimating the acoustic transfer function, the signal level of the sound source signal
is within the predetermined range. Alternatively, the sound source signal may be determined to
be effective for estimation of the acoustic transfer function. With such a configuration, when a
sound source signal having an unnecessarily high signal level such as noise or illegal radio waves
is input, the sound source signal is not determined to be effective for estimation of the acoustic
transfer function, and hence the estimation unit 40 in the latter stage It is possible to prevent in
advance the degradation of the estimation accuracy of the partial acoustic transfer function.
[0034]
It should be noted that whether the sound source signal is effective for estimation of the sound
transfer function can be determined based on an arbitrary value, as long as it can determine the
strength of the sound source signal, such as voltage value, current value, and amplitude value of
each sound source signal. The determination may be made.
[0035]
The estimation unit 40 represents an acoustic transfer function in a partial frequency band of the
sound source signal and the sound collection signal based on the sound source signal and the
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sound collection signal determined to be effective for the estimation of the acoustic transfer
function by the determination unit 30. It is a processing unit that estimates a partial acoustic
transfer function.
[0036]
The estimation unit 40 uses the speaker 201 based on the difference between the sound source
signal whose signal level is equal to or higher than the predetermined signal level and the sound
collection signal in the same partial frequency band as the sound source signal according to a
known arithmetic equation for calculating the acoustic transfer function. The acoustic
characteristic in each partial frequency band in the space between the microphones 202 is
calculated, the ideal partial acoustic transfer function is calculated from the acoustic
characteristic, and the calculation result is output to the storage unit 50.
[0037]
For example, when the sound source signal as shown in FIG. 4A is input to the dividing unit 20 at
time (t), the estimation unit 40 receives the sound source signal in the low frequency region L
from the determination unit 30. As shown in FIG. 4B, only the acoustic characteristic of the low
frequency band L is calculated, and the partial acoustic transfer function of the low frequency
band L obtained from the acoustic characteristic is stored in the storage unit 50 in the
subsequent stage.
[0038]
As described above, the sound source signal in the low frequency band L input to the
determination unit 30 at this time is a signal having a signal level equal to or higher than the
threshold and having a constant signal level like white noise. For the low frequency band L, the
unit 30 can calculate the acoustic characteristics of the space with the same reproducibility as
when white noise is used.
[0039]
Further, when a sound source signal as shown in FIG. 4C is input to the dividing unit 20 at time (t
+ 1), the estimation unit 40 receives only the sound source signal in the high frequency band H
from the determination unit 30. Therefore, as shown in FIG. 4D, only the acoustic characteristics
related to the high frequency band H are calculated, and the partial acoustic transfer function
related to the high frequency band H obtained from the acoustic characteristics is stored in the
storage unit 50 in the subsequent stage.
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[0040]
At this time, since the sound source signal in the high frequency band H input to the
determination unit 30 is a signal having a signal level equal to or higher than the threshold and
having a constant signal level like white noise, the determination unit 30 With regard to the band
H, the acoustic characteristics of the space can be calculated with the same reproducibility as
when white noise is used.
[0041]
The storage unit 50 stores a partial acoustic transfer function for each partial frequency band.
The storage unit 50 corresponds to a memory in which a partial acoustic transfer function and a
filter coefficient are set in synthesis filter units 51 and 52 (see FIG. 6) described later.
[0042]
Here, with reference to FIG. 5, the procedure in which each partial acoustic transfer function is
stored (set) in the storage unit 50 will be described.
FIG. 5 is an explanatory view showing a procedure in which each partial acoustic transfer
function is stored in the storage unit.
In FIGS. 5A to 5E, the high frequency band H is indicated by H, the low frequency band L is
indicated by L, and the partial acoustic function is indicated by Y. The partial acoustic transfer
function Y in Y is indicated by YL.
Note that the parentheses in the side of YH and YL indicate the time when the sound source
signal is input to the sound adjustment device 10.
[0043]
In the state (time (0)) before the sound source signal is input to the sound adjustment apparatus
10 of the present embodiment, the storage unit 50 stores a standard high frequency band as an
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initial value as shown in FIG. A partial acoustic transfer function YH (0) in the equation (4) and a
partial acoustic transfer function YL (0) in a standard low frequency band are stored.
[0044]
Thereafter, at time (t), it is assumed that the sound source signal is input to the sound adjustment
device 10.
At this time, when it is determined that only the sound source signal in the high frequency band
H is effective for the estimation of the sound transfer function with respect to the inputted sound
source signal, the storage unit 50 stores time as shown in FIG. And the partial acoustic transfer
function YH (t) of the high frequency band H in.
Here, since the sound source signal in the low frequency band L is determined to be invalid, the
partial acoustic transfer function YL (0) in the low frequency band L stored as the initial value is
held without being updated.
[0045]
Next, at time (t + 1), when it is determined that only the low frequency band L is effective for the
estimation of the acoustic transfer function with respect to the sound source signal input to the
acoustic adjustment device 10, the storage unit 50 illustrated in FIG. As shown in (c), the partial
acoustic transfer function Y in the low frequency band L is updated to the partial acoustic
transfer function YL (t + 1) in the low frequency region L at time (t + 1) and stored.
Here, since the sound source signal in the high frequency band H is determined to be invalid, the
partial acoustic transfer function YH (t) in the high frequency band H is held without being
updated.
[0046]
After that, when it is determined that only the high frequency band H is effective for estimation
of the acoustic transfer function with respect to the sound source signal input to the acoustic
adjustment device 10 at time (t + 2), the storage unit 50 illustrated in FIG. , The partial acoustic
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transfer function YH (t + 1) in the high frequency band H is updated to YH (t + 2), and the partial
acoustic transfer function YL (t + 1) in the low frequency band L is maintained .
[0047]
Then, when it is determined that only the low frequency band L is effective for the estimation of
the acoustic transfer function with respect to the sound source signal input to the sound
adjustment device 10 at time (t + 3), partial sound in the high frequency band H is similarly The
transfer function YH (t + 2) is held, and the partial acoustic transfer function YL (t + 1) in the low
frequency band L is updated to YL (t + 3).
[0048]
The synthesis unit 60 is a processing unit that synthesizes the partial acoustic transfer functions
estimated by the estimation unit 40 for a plurality of partial frequency bands.
The synthesis unit 60 synthesizes the partial acoustic transfer functions for each partial
frequency band stored in the storage unit 50 to generate an acoustic transfer function
corresponding to the acoustic characteristics of the entire frequency band in the audible range.
[0049]
For example, in the synthesis unit 60, acoustic characteristics as shown in FIGS. 4B and 4D are
calculated by the estimation unit 40, and partial acoustic transfer functions obtained from these
acoustic characteristics are stored in the storage unit 50. As shown in FIG. 4E by combining the
partial acoustic transfer function of the low frequency band L and the partial acoustic transfer
function of the high frequency band H stored in the storage unit 50 at that time. The acoustic
characteristics of the space can be reproduced well for all frequency bands in the audible range.
[0050]
As described above, in the sound adjustment device 10 according to the present embodiment, the
sound source signal of colored sound input from the reproduction device 200 is divided into a
plurality of partial frequency bands, and the signal levels of the divided sound source signals are
equal to or higher than a predetermined signal level. When it is determined that the sound
source signal is determined, the partial sound transfer function in the partial frequency band of
the sound source signal is estimated.
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[0051]
Therefore, in this sound adjustment apparatus 10, each partial acoustic transfer function for each
partial frequency band estimated by the estimation unit 40 uses a sound source signal having a
constant signal level, as in the case of using white noise. Since partial acoustic transfer functions
for each frequency band can be estimated, by combining these partial acoustic transfer functions
by the synthesis unit 60, spatial acoustic characteristics can be reproduced well for all frequency
bands in the audible range. can do.
[0052]
Moreover, in the sound adjustment device 10, the partial sound transfer function stored in the
storage unit 50 is updated to the latest one each time the sound source signal is determined to be
effective for estimation of the sound transfer function while the sound source signal is input.
Therefore, for example, even if the acoustic characteristics of the space change during the
reproduction of music, the partial acoustic transfer function is changed at any time according to
the change of the acoustic characteristics to be ideal according to the change of the environment.
An acoustic transfer function can be obtained.
[0053]
Here, a more specific configuration of the acoustic adjustment device 10 according to the present
embodiment and the flow of signals in the acoustic adjustment device 10 will be described with
reference to FIG.
FIG. 6 is an explanatory view showing a detailed configuration of the sound adjustment device
10. As shown in FIG.
[0054]
As shown in FIG. 6, the sound adjustment apparatus 10 includes a synchronization unit 71, a
frequency conversion unit 81 for a sound source signal, a frequency conversion unit 82 for a
sound collection signal, a high pass filter unit 21 for a sound source signal, a low pass filter unit
22, 1/2 down-sampling units 91 and 92, high-pass filter unit 23 for sound collection signal, lowpass filter unit 24, 1/2 down-sampling units 93 and 94, level check units 31 and 32 for sound
source signals, adaptive control unit 41 , 42, a 2-up sampling unit 95, 96, a synthesis filter unit
51, 52, an addition unit 61, an adaptive filter unit 62, and an inverse frequency conversion unit
100.
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[0055]
The sound adjustment apparatus 10 is configured by a DSP (Digital Signal Processor) including a
central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM).
The synchronization unit 71, the frequency conversion unit 81, the frequency conversion unit
82, the high pass filter unit 21, the low pass filter unit 22, and 1/2 down sample are executed by
executing the predetermined acoustic adjustment program stored therein using the RAM as a
work area. Sections 91 and 92, high pass filter section 23, low pass filter section 24, 1/2 down
sampling sections 93 and 94, level check sections 31 and 32, adaptive control sections 41 and
42, 2 up sampling sections 95 and 96, synthesis filter section It functions as 51, 52, the addition
part 61, the adaptive filter part 62, the reverse frequency conversion part 100 grade | etc.,.
[0056]
The synchronization unit 71 delays the sound source signal input from the reproduction device
200 to synchronize the phases of the sound source signal and the sound collection signal, and
then outputs the sound source signal to the frequency conversion unit 81.
[0057]
The frequency converter 81 for the sound source signal converts the sound source signal input
from the synchronization unit 71 into a frequency domain by FFT (Fast Fourier Transform: Fast
Fourier Transform), and then outputs it to the high pass filter 21 and the low pass filter 22. At
the same time, the sound source signal converted to this frequency domain is output to the
adaptive filter 62.
[0058]
The frequency conversion unit 82 for collected sound signal converts the collected sound signal
input from the microphone 202 into a frequency domain by FFT, and outputs the converted
signal to the high pass filter unit 23 and the low pass filter unit 24.
[0059]
The high pass filter unit 21 for the sound source signal cuts the low frequency band L
component of the sound source signal converted into the frequency domain, generates a sound
source signal of only the high frequency band H component, and outputs it to the 1⁄2 down
sample unit 91 .
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In addition, the low pass filter unit 22 for the sound source signal cuts the high frequency band
H component of the sound source signal converted into the frequency domain, generates the
sound source signal of only the low frequency band L, and outputs it to the 1⁄2 down sample unit
92 Do.
[0060]
Similarly, the high pass filter unit 23 for the sound collection signal outputs the sound collection
signal of only the high frequency band H component to the 1/2 down sampling unit 93, and the
low pass filter unit 24 for the sound collection signal has a low frequency band L The pickup
signal of only the component is output to the 1/2 down-sampling unit 94.
[0061]
The 1/2 down-sampling units 91 and 92 for sound source signals sample (down-sample) each
sound source signal input thereto at a sampling frequency that is 1/2 times the frequency of the
sound source signal, and then each 1/2 down sample Output to level check units 31 and 32
subsequent to units 91 and 92.
[0062]
The 1⁄2 down-sampling units 93 and 94 for the sound collection signal sample (down-sample)
the sound collection signals input thereto at a sampling frequency that is 1⁄2 times the sound
collection signal frequency, and then 1⁄2 down. It is output to the adaptive control units 41 and
42 subsequent to the sample units 93 and 94.
[0063]
The level check units 31 and 32 determine whether the signal level of the sound source signal
input to each is equal to or higher than a predetermined signal level, and the sound source
signals determined to have a signal level equal to or higher than the predetermined signal level It
outputs to the adaptive control units 41 and 42 in the latter stage.
On the other hand, when the level check units 31 and 32 determine that the signal level has not
reached the predetermined signal level, the level check units 31 and 32 discard the signal
without outputting it to the adaptive control units 41 and 42.
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[0064]
The adaptive control units 41 and 42 calculate the acoustic characteristic in each partial
frequency band based on the sound source signal and the collected signal input to each, and the
partial acoustic transfer function corresponding to each acoustic characteristic obtained The
identification processing is performed (determined) and the identification processing is
performed, and the signal to which the partial acoustic transfer function after the identification
processing is applied is output to the second up-sampling units 95 and 96 at the subsequent
stage of each of the adaptive control units 41 and 42.
[0065]
The 2-up-sampling units 95 and 96 sample (up-sample) the signals input thereto at a sampling
frequency twice that of the signal frequency, and then output the signals to the synthesis filter
units 51 and 52 in the subsequent stage.
[0066]
The synthesis filter units 51 and 52 are adaptive filters that self-adapt a partial acoustic transfer
function in each partial frequency band in accordance with a known optimization algorithm, and
each partial is based on a signal input thereto. Self-adapt the filter coefficients to which the
partial acoustic transfer function in the frequency band is applied.
Each of the synthesis filter units 51 and 52 updates the partial acoustic transfer function and the
filter coefficient based on the signal each time a signal is input from the 2-up sampling unit 95 or
96 at the previous stage.
[0067]
The adding unit 61 adds the high frequency band H synthesis filter 51 and the low frequency
band L synthesis filter 52 together.
By the addition processing of the addition unit 61, the filter coefficient in the subsequent
adaptive filter unit 62 is determined.
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That is, as a result of this addition processing, the filter coefficient of synthesis filter unit 51 is set
as the filter coefficient in high frequency band H of adaptive filter unit 62, and the filter
coefficient of synthesis filter unit 52 is the filter in low frequency band L of adaptive filter unit
62 It is set as a factor.
[0068]
The adaptive filter unit 62 performs filter processing according to the filter coefficient set at that
time on the excitation signal converted into the frequency domain input from the frequency
conversion unit 81, and outputs the result to the inverse frequency conversion unit 100. .
[0069]
The inverse frequency transform unit 100 transforms the sound source signal in the frequency
domain input from the adaptive filter unit 62 into the time domain by IFFT (Inverse Fast Fourier
Transform), and outputs the transformed signal to the speaker 201.
[0070]
Next, processing performed by the CPU of the DSP when the sound adjustment apparatus 10
performs sound adjustment will be described with reference to FIG.
FIG. 7 is a flowchart showing the flow of processing when the CPU of the DSP executes the sound
adjustment program.
[0071]
As shown in FIG. 7, the CPU first executes synchronization processing to synchronize the phases
of the sound source signal and the sound collection signal (step S101), and then performs
frequency conversion to convert the sound source signal and the sound collection signal into the
frequency domain. A process is performed (step S102).
[0072]
Subsequently, the CPU executes division processing for dividing the sound source signal and the
sound collection signal converted into the frequency domain into the high frequency band H and
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the low frequency band L, respectively (step S103), and then one of each signal frequency The
down-sampling process is executed at a sampling frequency of 1/2.
[0073]
Here, the CPU determines for each sound source signal of each partial frequency band subjected
to the down-sampling process whether or not the sound source signal has an acoustic transfer
function by determining whether the signal level is equal to or higher than a predetermined
signal level. A process of determining whether it is effective for estimation is executed (step
S105).
[0074]
Then, when the CPU determines that the sound source signal is effective for estimation of the
acoustic transfer function (step S105: Yes), in the partial frequency band based on the sound
source signal and the sound collection signal having the same partial frequency band. The
identification process for estimating the partial acoustic transfer function is executed (step S106),
and then the updating process for updating the partial acoustic transfer function being set to the
partial acoustic transfer function obtained by this identification process is executed (step S107) ),
The process proceeds to step S108.
On the other hand, when the CPU determines in step S105 that the sound source signal is not
effective for the estimation of the acoustic transfer function (step S105: No), the CPU moves the
process to step S108.
[0075]
Subsequently, the CPU executes up-sampling processing (step 108), and thereafter executes
combining processing for combining the combining filter unit 51 in the high frequency band H
and the combining filter unit 52 in the low frequency band L (step S109). .
[0076]
Then, the CPU executes convolution processing by the adaptive filter unit 62 on the sound source
signal (step S110), and then executes inverse frequency conversion processing for converting the
sound source signal subjected to the convolution processing into the time domain. (Step S111),
the post-processing output to the speaker 201 is ended.
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[0077]
As described above, the sound adjustment apparatus 10 according to the present embodiment
uses the sound source signal, which is not the white noise but the colored sound input from the
reproduction apparatus 200, for identifying the sound transfer function. The identification of the
acoustic transfer function does not impair the listener's comfort.
[0078]
Further, the sound adjustment device 10 converts the sound source signal input from the
reproduction device 200 into a frequency domain and divides the sound source signal into a
plurality of partial frequency bands, and checks the signal level of the sound source signal for
each partial frequency band. Since the partial acoustic transfer function in the partial frequency
band is identified based on the sound source signal determined that the signal level is equal to or
higher than the predetermined signal level and the sound collection signal in the same partial
frequency band as the sound source signal. Even in the case where the signal level input from the
reproducing apparatus 200 changes with time, in the partial frequency band in which the signal
level of the sound source signal is equal to or higher than the predetermined signal level, spatial
acoustic characteristics are reproduced well. As a result, identification of a partial acoustic
transfer function can be suitably performed.
[0079]
Then, in the sound adjustment apparatus 10, in the partial frequency band determined that the
signal level of the sound source signal divided for each partial frequency band is equal to or
higher than the predetermined signal level, the synthesis filter unit corresponding to the partial
frequency band In the partial frequency band in which the filter coefficient of 51, 52 is updated
and the signal level of the sound source signal is determined to be less than the predetermined
signal level, the filter coefficient of the synthesis filter unit 51, 52 corresponding to the partial
frequency band is selected. Keep the previously updated filter coefficients without updating.
[0080]
Therefore, when a sound source signal that is not suitable for identification of a partial acoustic
transfer function, such as a sound source signal with a very low signal level, is input in the sound
adjustment device 10, the sound adjustment device 10 Since the filter coefficients are not
updated, it is possible to prevent the reduction in the reproducibility of the acoustic
characteristics.
[0081]
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In the embodiment described above, in the state before the sound source signal is input to the
sound adjustment device 10, the storage unit 50 includes, as an initial value, a partial sound
transfer function in a standard high frequency band and a standard low frequency band. When
the input of the sound source signal is stopped, the storage unit 50 receives the next sound
source signal as the partial sound transfer function stored at that time. Hold up to.
[0082]
Thereby, when the sound adjustment apparatus 10 is applied to a car-mounted audio system or
the like, even if the engine is stopped during music reproduction, the engine is stopped in the
storage unit 50 when the engine is restarted. Since each partial acoustic transfer function at the
time of making it hold | maintained, the time required to identification of an acoustic transfer
function can be shortened.
[0083]
DESCRIPTION OF SYMBOLS 10 sound adjustment apparatus 20 division part 30 determination
part 40 estimation part 50 memory | storage part 60 synthetic | combination part 200
reproduction apparatus 201 speaker 202 microphone 203 listener
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