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JP2014168116

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DESCRIPTION JP2014168116
Abstract: To make it possible to generate an appropriate sound field in headphones. An audio
signal processing apparatus 100 acquires headphone characteristics from an audio signal output
unit 51 of a headphone 50 to a sound receiving point in an ear canal in a headphone
characteristic acquisition unit 21 and acquires headphone characteristics acquired in an inverse
filter generation unit 22. The audio signal output unit corrects the phase characteristics of the
inverse filter generated in the phase characteristic processing unit 23 so as to be linear phase
characteristics in the audio signal output unit, and the convolution processing unit 31 receives
the input from the input unit 10. The audio signal is subjected to the process of convolving the
characteristic of the inverse filter subjected to the phase correction process, and the output unit
40 outputs the audio signal in which the characteristic of the inverse filter is convoluted.
[Selected figure] Figure 1
Audio signal processing apparatus, audio signal processing method, audio signal processing
program and headphone
[0001]
The present invention relates to an audio signal processing apparatus, an audio signal processing
method, an audio signal processing program, and headphones for generating an appropriate
sound field in headphones.
[0002]
Various methods of sound image localization have been proposed for the reproduction of audio
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1
signals by headphones.
For example, an impulse response of the inverse transfer function of a speaker or headphone
transfer function, an impulse response of the inverse transfer function of the external ear
transfer function, an impulse response of a head transfer function to an audio signal to obtain an
external sound image localization (Patent Document 1, Patent Document 2).
[0003]
JP-A-10-257599 JP-A-05-252598
[0004]
In the generation of the inverse filter disclosed in each of the above-mentioned patent
documents, for example, δ with a delay amount such that the least square error as a result of
convolving the inverse filter characteristic with the original transfer function using the least
squares method is minimized. Generate an inverse filter to be a function.
The audio data reproduced by the headphone, which has this inverse filter characteristic, has a
linear phase at the sound receiving point. The sound receiving point mentioned here is a
measurement position of the external ear transfer function in the external ear canal.
[0005]
In the case of acquiring inverse filter characteristics using a microphone in the ear canal each
time a user wears headphones using such a conventional technique, it is possible to generate an
appropriate inverse filter for each wearing. However, in the normal headphone usage form,
inverse filter characteristic acquisition for each wearing is not practical. In addition, since the
mounting position is slightly different each time the headphones are replaced, it is appropriate to
use the inverse filter characteristic once generated or to use the inverse filter generated by
another user or a dummy head. Can not listen by
[0006]
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Furthermore, in the conventional generation of the inverse filter, the delay amount of each
channel of the audio data output from the headphone is determined in order to obtain the
inverse filter to be the δ function with the delay amount that minimizes the minimum squared
error. May differ. In such a case, the sound image may not be localized at the center but may be
biased to either the left or the right.
[0007]
The present invention has been made in view of such problems, and the sound field does not
become unnatural even when the mounting position is shifted due to headphone replacement
and the like, and the sound image generated in the process of generating the reverse filter It is an
object of the present invention to provide an audio signal processing device, an audio signal
processing method, an audio signal processing program, and a headphone, which can eliminate
the left / right bias of the device.
[0008]
In order to achieve the above object, the audio signal processing apparatus (200) according to
the present invention has a phase characteristic to the headphone characteristic from the audio
signal output unit (51) of the headphone (50) to the sound receiving point in the ear canal An
inverse filter acquisition unit (25) for acquiring an inverse filter corrected to have a linear phase
characteristic in the audio signal output unit (51), and convoluting the characteristic of the phase
corrected inverse filter into the input audio signal And a convolution processing unit (30) for
performing processing.
[0009]
In the audio signal processing method according to the present invention, the audio signal output
unit (51) has phase characteristics with respect to headphone characteristics from the audio
signal output unit (51) of the headphone (50) to the sound receiving point in the ear canal. It is
characterized by comprising: an inverse filter acquisition step of acquiring an inverse filter
corrected to be a linear phase characteristic; and a convolution processing step of convoluting a
characteristic of the phase corrected inverse filter into an input audio signal. I assume.
[0010]
In the audio signal processing program according to the present invention, the computer (20, 30)
included in the audio signal processing device (200) includes the audio signal output unit (51) of
the headphone (50) to the sound receiving point in the ear canal. Reverse filter acquisition step
of acquiring an inverse filter corrected so that phase characteristics in the audio signal output
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unit (51) become linear phase characteristics with respect to headphone characteristics, the
phase-corrected inverse to the input audio signal And performing a convolution process step of
performing a process of convoluting filter characteristics.
[0011]
The audio signal processing apparatus (100) according to another aspect of the present
invention is a headphone characteristic acquiring unit (acquiring headphone characteristics from
the audio signal output unit (51) of the headphone (50) to the sound receiving point in the ear
canal 21) an inverse filter generation unit (22) that generates an inverse filter of the headphone
characteristic, and a phase correction that corrects the phase characteristic of the inverse filter to
be a linear phase characteristic in the audio signal output unit (51) The processing section (23) is
characterized by comprising a convolution processing section (31) for performing processing of
convoluting the characteristic of the inverse filter subjected to the phase correction processing to
the input audio signal.
[0012]
In the audio signal processing method according to another aspect of the present invention, a
headphone characteristic acquiring step of acquiring a headphone characteristic from an audio
signal output unit (51) of the headphone (50) to a sound receiving point in the ear canal, the
headphone characteristic Inverse filter generation step of generating an inverse filter, phase
correction processing step of correcting the phase characteristic of the inverse filter so as to be
linear phase characteristic in the audio signal output unit (51), and input audio signal And a
convolution process step of convoluting the characteristics of the inverse filter subjected to the
phase correction process.
[0013]
In the audio signal processing program according to another aspect of the present invention, the
computer (20, 30) included in the audio signal processing device (100) receives the audio signal
output unit (51) of the headphone (50) in the ear canal. A headphone characteristic acquisition
step of acquiring headphone characteristics up to a sound point, an inverse filter generation step
of generating an inverse filter of the headphone characteristics, and a phase characteristic of the
inverse filter being a linear phase characteristic in the audio signal output unit (51) And a
convolution processing step of convoluting the characteristics of the inverse filter subjected to
the phase correction processing to the input audio signal.
[0014]
According to the present invention, it is possible to prevent the sound field from becoming
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unnatural even when the mounting position is shifted due to the replacement of headphones, and
to eliminate the lateral deviation of the sound image generated in the process of generating the
inverse filter. .
[0015]
It is a structure block diagram of the audio signal processing apparatus concerning the 1st
Embodiment of this invention.
It is a flowchart which shows the process in the audio signal processing apparatus concerning
the 1st Embodiment of this invention.
It is the figure which showed the measurement state of the headphone characteristic typically.
It is a flowchart which shows the process in the audio signal processing apparatus concerning
the 1st Embodiment of this invention.
It is a structure block diagram of the audio signal processing apparatus concerning the 2nd
Embodiment of this invention.
It is a flowchart which shows the process in the audio signal processing apparatus concerning
the 2nd Embodiment of this invention.
It is a structure block diagram of the headphones which concern on the 3rd Embodiment of this
invention.
It is a structure block diagram of the headphones which concern on the 4th Embodiment of this
invention.
It is the figure which showed the frequency characteristic by the replacement of headphones. It is
a figure which contrasted the error signal before and behind at the time of headphone
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replacement in the case where a prior art is applied. It is the figure which contrasted the
difference | error signal before and behind in the headphone replacement in the case where this
invention is applied.
[0016]
Hereinafter, the configuration of the audio signal processing device 100 according to the first
embodiment of the present invention will be described with reference to FIG.
[0017]
As an example of the audio signal processing device 100, various devices that are connected to
the headphone 50 and can supply an audio signal to the connected headphone 50 correspond.
Specifically, it is a stationary or portable audio device, an information terminal or the like.
[0018]
FIG. 1 shows an example of the configuration of an audio signal processing apparatus 100. The
audio signal processing apparatus 100 includes an input unit 10, a central processing unit (CPU)
20, a digital signal processor (DSP) 30, and an output unit 40. . The audio signal processed by the
audio signal processing apparatus 100 is input to the headphone 50 from the output unit 40. In
the case of stereo headphones, the headphone 50 includes an audio signal output unit 51L for
the left channel and an audio signal output unit 51R for the right channel.
[0019]
The processing according to the present invention is realized by the processing by the CPU 20
and the DSP 30 that constitute the audio signal processing device 100. Therefore, the audio
signal processing apparatus 100 may be realized by installing a program for operating the audio
signal processing apparatus 100 in various information terminals in addition to a dedicated
apparatus. In the processing of the CPU 20 and the DSP 30, program data or the like recorded on
a random access memory (RAM) or a read only memory (ROM) and further on another recording
medium is used as appropriate. Further, each component constituting the audio signal processing
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device 100 operates under the control of the CPU 20 based on a predetermined program.
[0020]
The input unit 10 is an interface or various recording media to which an audio signal is input. An
audio signal input here is, for example, a stereo signal composed of left and right channel signals.
The input unit 10 is an interface through which an audio signal reproduced by an external device
is input, and audio data recorded in various recording media readable by the audio signal
processing device 100 is processed by the CPU 20 or the DSP 30. You may have the function to
reproduce | regenerate.
[0021]
The CPU 20 operates as the headphone characteristic acquisition unit 21, the inverse filter
generation unit 22, and the phase correction processing unit 23 according to the operating
program.
[0022]
The headphone characteristic acquisition unit 21 acquires, as headphone characteristics, the
headphone 50 connected to the audio signal processing apparatus 100 and the impulse
characteristic up to an arbitrary point of the ear canal 81 of the user wearing the headphone 50.
The headphone characteristics acquired by the headphone characteristics acquisition unit 21
acquire the characteristics for each of the left and right channels when the audio signal is
configured by the left and right channels.
[0023]
The inverse filter generation unit 22 generates inverse filters (HL, HR) for the headphone
characteristics (HpLe, HpRe) acquired by the headphone characteristic acquisition unit 21. The
generation of the inverse filter by the inverse filter generation unit 221 is based on the existing
least squares method or the like.
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[0024]
The phase correction processing unit 23 causes the phase characteristics of the inverse filter to
be linear phase characteristics in the audio signal output unit 51 included in the headphone 50
with respect to the inverse filters (HL and HR) generated by the inverse filter generation unit 22.
Perform processing to correct. Let (H <'> L, H <'> R) be the inverse filters subjected to the phase
correction. In this case, the position of the linear phase is a sound emission surface or sound
emission point such as a diaphragm provided in the audio signal output unit 51.
[0025]
The convolution processing unit 31 performs processing of convoluting an inverse filter (H <'> L,
H <'> R) phase-corrected in the phase correction processing unit 23 with the audio signal input
from the input unit 10.
[0026]
The output unit 40 outputs the audio signal in which the inverse filters (H <'> L, H <'> R) are
convoluted in the convolution processing unit 31 to the headphone 50.
The output unit 40 is various interfaces for outputting an audio signal to the headphone 50, and
may include an amplification function for amplifying the audio signal output from the
convolution processing unit 31.
[0027]
The configuration of the audio signal processing apparatus 100 includes, in addition to the
components shown in FIG. 1, for example, various necessary components and control functions
not shown other than the power supply function for operating each part of the apparatus.
[0028]
Next, processing by the audio signal processing device 100 according to the first embodiment of
the present invention will be described using FIGS. 2 to 4.
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The following processing is described as an audio signal being a stereo signal consisting of a left
channel and a right channel. In addition, each process may execute processes for the left channel
and the right channel, respectively, or may simultaneously process in parallel.
[0029]
Based on FIG. 2, first, as described above, the headphone characteristic acquisition unit 21 sets
the headphone 50 connected to the audio signal processing apparatus 100 and the impulse
characteristic up to an arbitrary point in the ear canal 81 of the user wearing the headphone 50
to headphones. It acquires as a characteristic (step S10).
[0030]
As an example of acquisition of headphone characteristics in step S10, acquisition of headphone
characteristics by measurement will be described using FIG.
FIG. 3 schematically shows a state in which the headphone 50 is attached to the ear 80 of the
user or the dummy head, and for convenience, only one of the right and the left is displayed.
[0031]
The headphone 50 includes an audio signal output unit 51 and a headphone code 53 that
supplies an audio signal to the audio signal output unit 51. The audio signal output unit 51
includes a diaphragm 52 that converts the audio signal into a sound wave. The form and driving
method of the headphones 50, the shape of the diaphragm 52, and the like are arbitrary.
[0032]
As shown in FIG. 3, the microphone 90 is disposed at an arbitrary position of the ear canal 81
with the headphones 50 attached. The microphone 90 is preferably close to the position of the
tympanic membrane, and is disposed at the tympanic position when a dummy head is used. The
microphone 90 is connected to the audio signal processing apparatus 100 by the microphone
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code 91, and the received audio signal is processed by the headphone characteristic acquisition
unit 21.
[0033]
The headphone characteristic acquisition unit 21 causes the audio signal output unit 51 to
output a measurement signal such as an impulse signal based on data stored in the ROM or the
like or a waveform generated by the DSP 30. The output measurement signal is received by the
microphone 90 via the space formed by the headphone 50 and the outer ear. The measurement
signal received by the microphone 90 is acquired as headphone characteristics (HpLe, HpRe)
including a delay or the like for each frequency component with respect to the original impulse
signal. The headphone characteristic is obtained as the headphone characteristic HpLe of the left
channel and the headphone characteristic HpRe of the right channel.
[0034]
Moreover, as another example of acquisition of the headphone characteristic in step S10, the
headphone characteristic measured in advance is acquired by reading out from any storage
medium which can be read by the audio signal processing apparatus 100. The headphone
characteristics acquired in this manner enable acquisition of different headphone characteristics
depending on the type of headphones connected to the audio signal processing apparatus 100.
In addition, headphone characteristics based on actual measurement of the user and the
headphone may be acquired.
[0035]
Returning to FIG. 2, after the headphone characteristics are acquired in step S10, the inverse
filter generation unit 22 generates inverse filters (HL, HR) with respect to the headphone
characteristics (HpLe, HpRe) acquired in step S10 (step S11). Here, HL is an inverse filter of
HpLe, and HR is an inverse filter of HpRe.
[0036]
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10
The inverse filter generation process in step S11 will be described. Based on the headphone
characteristics HpLe and HpRe acquired in step S10, the signal processing algorithm for
generating the inverse filter of the linear filter is used to generate the coefficient filters HL and
HR having the inverse characteristic to the original signal. There are various algorithms such as
the least squares method and the minimum phase method as an algorithm for generating the
inverse filter of the linear filter, but in the present invention, the least squares algorithm is used.
When generating the inverse filters HL and HR, the delay amount (spike point) is inserted as an
optimal delay amount so that the values of the HL and HR errors are minimized at the left and
right.
[0037]
When the inverse filters (HL and HR) generated in step S11 are convoluted into the audio signal
without performing the phase correction processing in step S12 shown below, the phase
becomes a linear phase at the position of the microphone 90 as a sound receiving point ing.
[0038]
After the inverse filters (HL, HR) are generated in step S11, the phase correction processing unit
23 sets the phase characteristics of the inverse filters to the headphones of the inverse filters
(HL, HR) generated by the inverse filter generation unit 22 as headphones. The audio signal
output unit 51 included in the F.50 performs correction processing so as to have linear phase
characteristics (step S12).
[0039]
The phase correction process in step S12 will be described with reference to FIG.
First, the phase correction processing unit 23 performs discrete Fourier transform on the inverse
filters (HL, HR) generated by the inverse filter generation unit 22 to calculate frequency
amplitude characteristics (step S121).
The frequency amplitude characteristic is calculated using Equation 1 and Equation 2.
[0040]
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11
[0041]
[0042]
Next, linear phase conversion processing is performed on the frequency amplitude characteristic
calculated in step S121 to form a linear phase filter in which the group delay characteristic is
constant and the phase characteristic is zero without changing the frequency characteristic (step
S122).
[0043]
The linear phase conversion in step S122 is performed using Equation 3 and Equation 4.
[0044]
[0045]
[0046]
Next, inverse discrete Fourier transform is performed at arbitrary N points using the results r ′
(ω) and i ′ (ω) resulting from linear phase transformation according to Equation 3 and
Equation 4 to restore the time axis waveform (step S123).
Next, group delay time exchange processing is performed on the time axis waveform of N points
obtained by the processing of step S123 (step S124).
[0047]
An example of the group delay time exchange process in step S124 is a process of exchanging
waveforms before and after the N / 2 point in the time axis waveform of N points, and Equations
5 and 6 are used.
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Equations 5 and 6 describe the processing for the right channel signal as an example, but the
processing is the same for the left channel.
[0048]
[0049]
[0050]
Returning to FIG. 2, the convolution processing unit 31 performs a process of convoluting the
inverse filter (H <'> L, H <'> R) phase-corrected in step S12 into the audio signal input from the
input unit 10 (step S13).
[0051]
The convolution process in step S13 will be described.
The inverse filters H <'> L and H <'> R phase-corrected in step S12 are subjected to a convolution
operation on the audio signal data input from the input unit 10 on the time axis or the frequency
axis.
The convolution operation may be performed on audio signal data in advance or may be
performed on an audio input signal subjected to reproduction buffering in real time.
When the convolution operation is performed in real time during playback, it is possible to
switch and present valid / invalid of the convolution processing during playback.
[0052]
Next, the configuration of an audio signal processing device 200 according to a second
embodiment of the present invention will be described with reference to FIG.
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The configuration of the audio signal processing device 200 is the inverse filter acquisition unit
25 instead of the headphone characteristic acquisition unit 21, the inverse filter generation unit
22, and the phase correction processing unit 23 which are realized by the processing of the CPU
20 for the audio signal processing device 100. The other configurations are the same.
[0053]
In the audio signal processing device 200, the phase-corrected inverse filters (H <'> L, H <'> R)
obtained by the processing from step S10 to step S12 in the first embodiment are audio signal
processing. It is premised that the information is recorded in various recording media that can be
read by the device 200.
[0054]
The inverse filter acquisition unit 25 performs processing for acquiring phase-corrected inverse
filters (H <'> L, H <'> R) recorded in various recording media.
[0055]
Next, processing by the audio signal processing device 200 according to the second embodiment
of the present invention will be described using FIG.
[0056]
First, the reverse filter acquisition unit 25 acquires reverse filters (H <'> L, H <'> R) that have
been phase-corrected in advance, which are recorded in an arbitrary recording medium such as a
ROM or a memory card. (Step S20).
The inverse filter acquired here is also an inverse filter based on the headphone characteristic
measured for each headphone using the user and the dummy head as in the first embodiment.
[0057]
It is preferable that the reverse filter acquired in step S20 be a reverse filter based on headphone
characteristics measured by headphones actually used by the user.
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In addition, even if the headphone characteristic is not the headphone characteristic measured by
the user but the headphone characteristic of the dummy head or another person, the user may
select the characteristic closest to the own headphone characteristic from among a plurality of
headphone characteristics.
Furthermore, the headphone characteristics of the dummy head and others may be adjusted to
be close to the headphone characteristics of the user, and the headphone characteristics may be
optimized.
In addition, the inverse filter (H <'> L, H <'> R) calculated in the audio signal processing apparatus
100 according to the first embodiment is stored in any storage medium, and the audio signal
according to the second embodiment is stored. It may be operated as the processing device 200.
[0058]
Next, the convolution processing unit 31 applies the inverse filters (H <'> L, H <'> R) acquired in
step S20 to the audio signal input from the input unit 10 as in the first embodiment. A folding
process is performed (step S21).
[0059]
Next, the configuration of a headphone 500 according to a third embodiment of the present
invention will be described with reference to FIG.
The headphone 500 has a configuration in which the audio signal processing device 100
according to the first embodiment is incorporated in the headphone 500.
[0060]
Therefore, the configuration of the headphone 500 corresponds to the configuration of the audio
signal processing device 100 shown in FIG.
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15
Further, the processing in each component constituting the headphone 500 also corresponds to
the processing of the audio signal processing device 100 shown in FIGS. 2 to 4.
The difference is that the output unit 540 outputs, to the audio signal output unit 551, the audio
signal in which the inverse filters (H <'> L, H <'> R) are convoluted in the convolution processing
unit 531. The output unit 540 may include an amplification function of amplifying the audio
signal output from the convolution processing unit 531.
[0061]
Next, the configuration of a headphone 600 according to a fourth embodiment of the present
invention will be described with reference to FIG. The headphone 600 has a configuration in
which the audio signal processing device 200 according to the second embodiment is
incorporated in the headphone 600.
[0062]
Therefore, the configuration of the headphone 600 corresponds to the configuration of the audio
signal processing device 200 shown in FIG. Further, the processing in each component
constituting the headphone 600 also corresponds to the processing of the audio signal
processing device 200 shown in FIG. The difference is that the output unit 540 outputs, to the
audio signal output unit 551, the audio signal in which the inverse filters (H <'> L, H <'> R) are
convoluted in the convolution processing unit 531. The output unit 540 may include an
amplification function of amplifying the audio signal output from the convolution processing unit
531.
[0063]
Next, the effect of each device according to each embodiment described above is verified. In the
following description, although it demonstrates based on 1st Embodiment, the same effect is
acquired also in another embodiment.
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[0064]
First, FIG. 9 shows an example of frequency characteristics when an audio signal is convoluted
with an inverse filter (HL, HR) for which the phase correction processing (step S12) is not
performed by the phase correction processing unit 23 and the headphones are redone. FIG. 9
shows the frequency characteristics with respect to the output of the audio signal output unit
51L that outputs the audio signal of the left channel every time the headphone is repeated ten
times.
[0065]
As shown in FIG. 9, since the inverse filters (HL and HR) are set to be appropriate at the position
of the microphone 90 at the time of acquiring the headphone characteristics, the frequency
characteristics are largely changed by the headphone replacement. I understand.
[0066]
Next, using FIG. 10 and FIG. 11 to compare the effects of the inverse filters (HL, HR) and the
inverse filters (H <'> L, H <'> R) subjected to the phase correction processing in the present
invention. explain.
For comparison, an error signal that is the difference between the original impulse signal and the
waveform when the inverse filter is convoluted with the impulse signal is used. The error signal
is a δ function in which an impulse waveform is present at the delay position when the inverse
filter is ideal. In the error signal of this comparative example, the maximum value of the impulse
waveform and the delay of the impulse waveform is replaced with 0.
[0067]
FIG. 10 shows measured values of error signals by inverse filters (HL, HR) not subjected to phase
correction, and the error signals in the case where the waveform before headphone replacement
is doubled again are respectively represented by the left channel and The right channel is shown.
[0068]
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17
In FIG. 10, the error signal before the replacement of the headphone is an error signal obtained
when the headphone characteristic acquisition unit measures and acquires the headphone
characteristic using the microphone 90.
On the other hand, when the headphones are re-hooked, the value of the error signal is larger
than before the re-hanging of the headphones for both re-hanging twice, the error due to the rehanging of the headphones is large, and every wearing of the headphones Measurement of
headphone characteristics using the microphone 90 is not appropriate for headphones that are
not realistic.
[0069]
FIG. 11 shows measured values of error signals by the inverse filters (H <'> L, H <'> R) subjected
to the phase correction processing according to the present invention, and the waveform before
headphone replacement is double repeated The left and right channels are shown for the error
signal in the case of FIG.
[0070]
In FIG. 11, the error signal before the headphone replacement is larger than the error signal
before the headphone replacement in FIG. 10, but the difference due to the headphone
replacement is small.
Therefore, by applying the present invention, it is possible to obtain natural sound image
localization with almost no sense of discomfort due to re-insertion of headphones.
[0071]
Further, the position at which the δ function is maximum when the inverse filter is convoluted
into the original impulse signal can represent the delay amount of the δ function as a spike
point, but when the present invention is applied, the group in step S124 By performing the delay
time switching process, the center of the total number of taps constituting the inverse filter is set
as the maximum value, and thus the coefficients are symmetrical. Further, the process of step
S124 is simultaneously performed on the left and right channels. For this reason, when the spike
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points in each channel coincide with each other, the delays in each channel coincide with each
other, and the left / right bias of the sound image can be eliminated.
[0072]
Further, in the present invention, since the phase is matched at the sound emitting surface or the
sound emitting point of the diaphragm or the like provided in the audio signal output unit 51, it
is possible to prevent the sound image from being biased to the left or right due to the
replacement of the headphones.
[0073]
As an application example of the present invention, it is possible to reproduce a sound field close
to the sound field at the recording position, for example, by inputting an audio signal by binaural
recording.
In addition, application to external localization headphones where the sound image is localized
outside the head of the user by convoluting the transfer characteristics from the sound source
position outside the user such as a speaker or the like to the headphone position worn by the
user or the user's ear It is possible. In addition, even in the case of input of audio data such as
ordinary stereo, headphone characteristics are appropriately canceled by the application of the
present invention.
[0074]
The embodiment of the present invention can be variously modified without departing from the
scope of the invention. For example, the phase correction processing in the phase correction
processing unit 23 or 523 may use another method as long as it is processing to switch the front
and back of an arbitrary N point time axis waveform. Similarly, other methods may be applied as
processing for the same purpose in other processing. In each of the above embodiments, the
audio signal of two channels consisting of the left channel and the right channel has been
described, but application to multi-channel is also possible.
[0075]
100, 200: audio signal processing apparatus 10, 510: input unit 20, 520: CPU 21, 521:
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headphone characteristic acquisition unit 22, 522: inverse filter generation unit 23, 523: phase
correction processing unit 25, 525: inverse filter acquisition Unit 30, 530: DSP 31, 531:
convolution processing unit 40, 540: output unit 50, 500, 600: headphones 51, 551: audio signal
output unit 52: diaphragm 81: ear canal 90: microphone
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