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JP2013085111

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DESCRIPTION JP2013085111
Abstract: To improve the sound quality of audio output. A phase difference between frequency
phase characteristics of band division filters 113-1 and 113-2 is set to 0 degree or 180 degrees.
An impulse signal is input without the correction filter 112 being added to the band division
filters 113-1 and 113-2, the amplification units 114-1 and 114-2, and the speakers 115-1 and
115-2 set in this manner. The voice output from the microphone is picked up by the microphone,
and the inverse filter when this result is used as the impulse response is taken as the correction
filter 112. As a result, since the correction filter 112 can simultaneously correct the audio signals
of both bands to be divided at the front stage of the band division filters 113-1 and 113-2, the
frequency of the sound output from the output unit 101 The amplitude characteristic is flat as a
whole, and the sound output is improved. The present technology can be applied to audio
players. [Selected figure] Figure 5
Voice processing apparatus and voice processing method, recording medium, and program
[0001]
The present technology relates to an audio processing device, an audio processing method, a
recording medium, and a program, and more particularly, to an audio processing device, an audio
processing method, a recording medium, and a program that can enhance audio output.
[0002]
In designing an acoustic device such as a multi-way speaker that outputs voice for each of a
plurality of bands, technology for measuring in advance the acoustic characteristics of the entire
acoustic device and enhancing the sound quality of voice output by inverse filter or equalizing
has become widespread ing.
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1
[0003]
It is known that the sound quality is degraded when the frequency amplitude characteristics and
the frequency phase characteristics of a plurality of speakers are broadened and reproduced in a
state of being respectively disturbed.
Therefore, it is considered possible to achieve high sound quality by correcting the frequency
amplitude characteristic and the frequency phase characteristic for each speaker.
However, when configuring DSP (Digital Signal Processor) using limited computing resources and
achieving high sound quality, correcting the audio output of each speaker is the limit of
computational resources and the limit of high sound quality. Become.
[0004]
Therefore, a technique has been proposed in which the audio signal is corrected by the
correction filter over the entire band before the band division, and then the band is divided and
output (see Patent Document 1).
[0005]
JP 2005-184040 A
[0006]
However, when a correction is applied to an audio signal including all bands before dividing the
band, the sound quality may be strange in the band near the crossover of each band divided by
the band dividing filter. It is done.
In order to cope with such incongruity, in order to improve the frequency amplitude
characteristic of the band near the crossover, a technique has been proposed in which a filter
whose gain is increased is configured for the band near the crossover. Not enough effect.
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[0007]
First of all, when a 2-way or 3-way speaker system intended for wide-band reproduction, or a 2.1
ch or 5.1 ch reproduction system is designed, a band division filter is configured from the
reproduction capability of each speaker unit, and the propagation delay of each speaker unit Are
corrected, and further, the level balance of the high band, the mid band, the low band, etc. is
corrected.
[0008]
However, after that, it is not considered to perform correction by signal processing using an
inverse filter in consideration of the characteristics of the speaker unit.
[0009]
For this reason, even if a speaker system using a plurality of speaker units is configured and
good characteristics are obtained to some extent, it may cause discomfort when the band near
the crossover is adjusted by signal processing.
[0010]
The present technology has been made in view of such a situation, and in particular, improves
the sound quality of the audio output by adjusting the frequency phase characteristic of the band
division filter instead of correcting the frequency amplitude characteristic. is there.
[0011]
An audio processing device according to one aspect of the present technology includes: a
plurality of speakers for outputting audio in each band; a correction filter for correcting an audio
signal including a plurality of bands according to the characteristics of the plurality of speakers;
And a plurality of band division filters for dividing the audio signal corrected by the plurality of
bands into the band of the speaker such that the phase difference between the respective phase
characteristics becomes approximately 0 degrees or approximately 180 degrees, and the
correction filter It is an inverse filter which is set by an impulse response based on voice output
for each band from the plurality of speakers via the plurality of band division filters.
[0012]
In the plurality of band division filters, only the predetermined frequency band among the audio
signals corrected by the correction filter is such that the phase difference of the respective phase
characteristics is approximately 0 degrees or approximately 180 degrees. It can be made to
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divide into the band of a speaker.
[0013]
An amplification unit for amplifying the audio signal may be further included, and the
amplification unit may be one amplification unit for amplifying the audio signal before being
divided by the band division filter, or A plurality of amplification units may be provided to
respectively amplify the audio signals of each band divided by the band division filter.
[0014]
The audio signal may further include an additional filter for adding the audio characteristic of
another audio processing apparatus, and the audio characteristic of the other audio processing
apparatus may be downloaded from a library connected by a network. Can be
[0015]
The additional filter may be one additional filter that adds the acoustic characteristic of the other
voice processing apparatus to the voice signal before being split by the band splitting filter, or
may be split by the band splitting filter A plurality of additional filters may be provided to add
the acoustic characteristics of the other voice processing apparatus for each band.
[0016]
The input audio signal is a multi-channel audio signal, which is a composite of audio signals
whose sound images are localized by a head related transfer function, and comprises the audio
processing device according to any one of claims 1 to 5. It can be an earphone.
[0017]
An audio processing method according to an aspect of the present technology is an audio
processing method of an audio processing apparatus including a plurality of speakers for
outputting audio in each band, and an audio signal including a plurality of bands is characterized
by the characteristics of the plurality of speakers. Correction filter processing for correcting in
response, and a plurality of audio signals corrected by the correction filter processing are divided
into the band of the speaker so that the phase difference of each phase characteristic becomes
approximately 0 degree or approximately 180 degrees The band division filter processing is
performed, and the correction filter is an inverse filter set by an impulse response based on voice
output for each band from the plurality of speakers via the plurality of band division filters.
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[0018]
A program according to one aspect of the present technology corrects a computer for controlling
an audio processing device including a plurality of speakers for outputting audio in each band, an
audio signal including a plurality of bands according to the characteristics of the plurality of
speakers Function as a correction filter and a plurality of band division filters for dividing the
audio signal corrected by the correction filter into the band of the speaker so that the phase
difference of each phase characteristic becomes approximately 0 degree or approximately 180
degrees The correction filter is an inverse filter that is set by an impulse response based on voice
output for each band from the plurality of speakers via the plurality of band division filters.
[0019]
A recording medium according to one aspect of the present technology has the program
according to claim 8 recorded thereon.
[0020]
In one aspect of the present technology, audio is output for each band by a plurality of speakers,
an audio signal including a plurality of bands is corrected according to the characteristics of the
plurality of speakers, and the corrected audio signal is The audio signal including the plurality of
bands is divided into the plurality of bands so that the phase difference of the phase
characteristics is approximately 0 degrees or approximately 180 degrees, and the audio signal
including the plurality of bands is divided from the plurality of speakers It is corrected by the
inverse filter set by the impulse response based on the voice output for each band.
[0021]
The audio processing device of the present technology may be an independent device or a block
that performs audio processing.
[0022]
According to the present technology, it is possible to improve the sound output of audio.
[0023]
It is a figure which shows the structural example of the output part to which the conventional
speech processing apparatus is applied.
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It is a figure explaining the frequency amplitude characteristic for every zone | band by the band
division filter of the output part of FIG.
It is a figure explaining the frequency phase characteristic for every zone | band by the band
division filter of the output part of FIG.
It is a figure explaining the frequency amplitude characteristic before amendment of an output
part of Drawing 1, and after amendment.
It is a figure showing an example of composition of a 1st embodiment of an output part to which
a voice processing device of this art is applied.
It is a figure explaining the correction filter which consists of an impulse response and an inverse
filter of an output part of FIG.
It is a figure explaining the frequency amplitude characteristic for every zone | band by the band
division filter of the output part of FIG.
It is a figure explaining the frequency phase characteristic for every zone | band by the band
division filter of the output part of FIG.
It is a figure explaining the ideal frequency amplitude characteristic of the output part of FIG.
It is a flowchart explaining the output processing by the output part of FIG.
It is a figure explaining the other example of the frequency phase characteristic for every zone |
band by the band division filter of the output part of FIG.
It is a figure showing the example of composition of the 1st modification of the output part to
which the speech processing unit of this art is applied.
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It is a flowchart explaining the output processing by the output part of FIG.
It is a figure showing the example of composition of the 2nd modification of the output part to
which the speech processing unit of this art is applied.
It is a flowchart explaining the output processing by the output part of FIG.
It is a figure showing the example of composition of the 3rd modification of the output part to
which the speech processing unit of this art is applied.
It is a flowchart explaining the output processing by the output part of FIG.
It is a figure which shows the structural example of the 4th modification of the output part to
which the speech processing unit of this art is applied. It is a flowchart explaining the virtual
reproduction | regeneration processing by the output part of FIG. It is a figure explaining the
example of composition of a general purpose personal computer.
[0024]
Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will
be described. The description will be made in the following order. 1. First Embodiment First
Modification 3. Second Modified Example Third Modified Example Fourth modification
[0025]
<1. First embodiment> [Configuration example of output unit to which conventional voice
processing apparatus is applied] In describing an output unit to which a voice processing
apparatus according to the present technology is applied, a configuration of an output unit to
which a conventional voice processing apparatus is applied Explain. FIG. 1 is a diagram for
explaining a configuration example of an output unit to which a conventional voice processing
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device is applied. The output unit in FIG. 1 outputs high quality sound based on the input audio
signal and outputs the audio.
[0026]
The output unit 1 outputs high quality sound based on the input audio signal consisting of an
analog signal and outputs audio. The output unit 1 includes an ADC (Analog Digital Converter)
11, a correction filter 12, band division filters 13-1 and 13-2, amplification units 14-1 and 14-2,
and speakers 15-1 and 15-2. ing.
[0027]
The ADC 11 converts an audio signal composed of an analog signal into a digital audio signal and
supplies the digital audio signal to the correction filter 12. The correction filter 12 measures the
sound signal output from the speakers 15-1 and 15-2 by the microphone when the impulse is
input without the filter, that is, without correction. It is an inverse filter obtained based on an
impulse response. Thereby, the sound output from the speakers 15-1 and 15-2 is corrected.
[0028]
The band division filters 13-1 and 13-2 are digital filters including, for example, Infinite impulse
response (IIR) filters, etc., and the audio signal corrected by the correction filter 12 is divided for
each band and amplified. It outputs to the sections 14-1 and 14-2. In FIG. 1, in the band division
filters 13-1 and 13-2, the band division filter 13-1 extracts an audio signal of a high frequency
band, and the band division filter 113-2 extracts an audio signal of a low frequency band. . The
amplification units 14-1 and 14-2 amplify audio signals in predetermined bands, respectively,
and output the amplified audio signals from the speakers 15-1 and 15-2. The speakers 15-1 and
15-2 have different frequency bands of the sound to be output, and in the example of FIG. 1, the
speaker 15-1 outputs an audio signal of a high frequency band, and the speaker 15-2 Outputs an
audio signal in a low frequency band. In FIG. 1, the amplification units 14-1 and 14-2 perform
digital signal amplification processing for amplifying digital audio signals, convert the signals
into analog signals, and output the analog signals to the speakers 15-1 and 15-2. However,
analog signal amplification processing may be performed after converting the digital audio signal
to analog.
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[0029]
The frequency amplitude characteristics of each of the band division filters 13-1 and 13-2 are
represented by waveforms L1 and L2 in FIG. 2, for example. That is, in the waveform shown by
the waveform L1, the frequency rises at -40 dB from around 100 Hz, and the frequency becomes
constant at about 1000 Hz to 0 dB. Further, the waveform shown by the waveform L2 is a convex
waveform whose frequency peaks near 200 Hz. Further, the crossover band of the waveforms L1
and L2 has a frequency of about 400 to 500 Hz. In FIG. 2, the horizontal axis indicates the
frequency band, and the vertical axis indicates the amplitude.
[0030]
The frequency phase characteristics of each of the band division filters 13-1 and 13-2 are shown
in FIG. That is, the waveform shown by the waveform L11 has a phase of 160 degrees at a
frequency of around 10 Hz, and the phase is gradually delayed as the frequency becomes higher,
and after being delayed to a frequency of -160 degrees at around 200 Hz, After the phase is
inverted and advanced 160 degrees, the phase gradually changes to approach 0 degrees. On the
other hand, the waveform shown by the waveform L12 has a phase of 160 degrees at a
frequency of 10 Hz, and the phase is gradually delayed as the frequency advances, after being
delayed to 0 degrees around 400 Hz, and thereafter gradually The phase changes as it
approaches 180 degrees. In FIG. 3, the horizontal axis indicates a frequency band, and the
vertical axis indicates a phase angle.
[0031]
The amplitude characteristic of the output section 1 without the correction filter 12 is an
amplitude waveform having unevenness with respect to the frequency band as shown in the
upper part of FIG. On the other hand, as shown in the lower part of FIG. 4 by the correction filter
12, the amplitude in each frequency band is made flat. However, there is a recess near 400 Hz,
which is near the crossover, and the flat amplitude characteristic is not obtained only near this
crossover. Conventionally, filter processing and equalizing processing have been performed as a
countermeasure for the recess. Incidentally, the recess in the lower part of FIG. 4 is generated in
a 2-way or 3-way speaker system, and in a system with one speaker, it becomes flat in each band
as shown in FIG. It is known to be an amplitude waveform. 4 and 9, the horizontal axis indicates
the frequency band, and the vertical axis indicates the amplitude in each frequency band.
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[0032]
[Configuration Example of First Embodiment of Output Unit to Which Speech Processing Device
of the Present Technology is Applied] Next, referring to FIG. 5, a first embodiment of an output
portion to which the speech processing device of the present technology is applied An exemplary
configuration of the form will be described. The output unit shown in FIG. 5 outputs high-quality
sound so as to have an ideal amplitude in the entire band based on the input audio signal, and
outputs audio.
[0033]
The output unit 101 outputs high quality sound based on the input audio signal including an
analog signal and outputs the audio. The output unit 101 includes an ADC (Analog Digital
Converter) 111, a correction filter 112, band division filters 113-1 and 113-2, amplification units
114-1 and 114-2, and speakers 115-1 and 115-2. ing.
[0034]
The ADC 111 is basically the same as the ADC 11, converts an audio signal composed of an
analog signal into a digital audio signal, and supplies the digital audio signal to the correction
filter 112. The correction filter 112 is basically the same as the correction filter 12, and in the
absence of this filter, that is, when an impulse is input without correction, the band division
filters 113-1 and 113- described later will be described. 2. An inverse filter obtained based on an
impulse response measured by collecting a sound signal output via the amplification units 114-1
and 114-2 and the speakers 115-1 and 115-2 by the microphone . Thereby, the sound output
from the speakers 115-1 and 115-2 is corrected.
[0035]
More specifically, when, for example, an impulse signal is input to the output unit 101, the
correction filter 112 does not have the correction filter 112 (when no correction is performed),
for example, the band division filters 113-1 and 113-2. , A waveform when the sound output
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through the amplification units 114-1 and 114-2 and the speakers 115-1 and 115-2 is collected
by the microphone, that is, an inverse filter set according to an impulse response It is. For
example, in the case of the impulse response as shown in the upper part of FIG. 6, the inverse
filter of the speaker system configured by the speakers 115-1 and 115-2 is as shown in the
middle part of FIG. That is, the correction filter 112 is an inverse filter as shown in the middle
stage of FIG. When an impulse signal is input in the state where such a correction filter 112 is
provided, the impulse response has a shaped waveform as shown in the lower part of FIG. In FIG.
6, the horizontal axis is the elapsed time (ms), and the vertical axis is the normalized amplitude.
[0036]
The band division filters 113-1 and 113-2 are digital filters made of, for example, Infinite
Impulse Response (IIR) filters, etc., and the phase difference between the frequency phase
characteristics of each band is approximately 0 degrees (or 180 degrees). The band division
filters 113-1 and 113-2 divide the audio signal corrected by the correction filter 112 for each
band and output the divided signals to the amplification units 114-1 and 114-2. In FIG. 5, in the
band division filters 113-1 and 113-2, the band division filter 113-1 extracts an audio signal of a
high frequency band, and the band division filter 113-2 is an audio signal of a low frequency
band. Extract.
[0037]
The amplification units 114-1 and 114-2 are basically the same as the amplification units 14-1
and 14-2, but respectively amplify audio signals of predetermined bands to obtain speakers 1151 and 115-. Output from 2 as voice. The speakers 115-1 and 115-2 are basically the same as the
speakers 15-1 and 15-2, and the frequency bands of the sounds to be output are different from
each other, and in the example of FIG. The speaker 115-1 outputs an audio signal of a high
frequency band, and the speaker 115-2 outputs an audio signal of a low frequency band. Also in
FIG. 5, the amplification units 114-1 and 114-2 perform digital signal amplification processing
for amplifying digital audio signals, convert the signals into analog signals, and output the analog
signals to the speakers 115-1 and 115-2. However, analog signal amplification processing may
be performed after converting the digital audio signal to analog.
[0038]
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The frequency amplitude characteristics of each of the band division filters 113-1 and 113-2 are
represented by, for example, waveforms L101 and L102 in FIG. 7, and the band division filters
13-1 and 13-2 described with reference to FIG. It is almost the same. That is, in the waveform
shown by the waveform L101, the frequency rises at 100 Hz to -40 dB, and the frequency
becomes constant at about 1000 Hz to 0 dB. Also, the waveform shown by the waveform L102 is
a convex curve that peaks near 200 Hz. The crossover band of the waveforms L101 and L102 is
around 300 to 400 Hz. In FIG. 7, the horizontal axis indicates the frequency band and the vertical
axis indicates the amplitude.
[0039]
Also, the frequency phase characteristics of each of the band division filters 113-1 and 113-2 are
different from the band division filters 13-1 and 13-2 illustrated in FIG. 8 and described with
reference to FIG. That is, the respective phase waveforms shown by the waveforms L111 and
L112 are completely coincident, that is, both phase differences are 0, the phase is 150 degrees in
the vicinity of 10 Hz, and gradually increases as the frequency increases. The phase is delayed
for the first time, and after the frequency is delayed to -160 degrees around 200 Hz, the phase is
inverted and advanced 160 degrees, and thereafter the phase gradually changes to approach 180 degrees. In FIG. 8, the horizontal axis indicates the frequency band and the vertical axis
indicates the phase angle.
[0040]
As a result, the amplitude for each frequency band of the audio signal output from the speakers
115-1 and 115-2 has a waveform that rises from -20 dB around 20 Hz and converges to 0 dB
around 200 Hz, as shown in FIG. Become.
[0041]
[Output Process by Output Unit of FIG. 5] Next, the output process by the output unit 101 of FIG.
5 will be described with reference to the flowchart of FIG.
[0042]
In step S1, the ADC 111 acquires the input analog audio signal.
[0043]
In step S2, the ADC 111 analog-to-digital converts the acquired analog audio signal into a digital
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audio signal, and supplies the digital audio signal to the correction filter 112.
[0044]
In step S3, the correction filter 112 performs correction filter processing on the supplied digital
audio signal, and supplies it to the band division filters 113-1 and 113-2.
[0045]
In step S4, the band division filters 113-1 and 113-2 extract voice signals in the high frequency
band and the low frequency band, respectively, and supply the voice signals to the amplification
units 114-1 and 114-2.
At this time, the band division filters 113-1 and 113-2 extract the audio signal for each
frequency band so that the phases of the divided audio signals coincide with each other
according to, for example, the frequency phase characteristic of FIG.
[0046]
In step S5, the amplification units 114-1 and 114-2 amplify the high frequency band audio signal
and the low frequency band audio signal supplied from the band division filters 113-1 and 1132, respectively. It converts into an analog signal and outputs it to the speakers 115-1 and 115-2.
[0047]
In step S6, the speakers 115-1 and 115-2 output voices in the high frequency band and voices in
the low frequency band, respectively.
[0048]
That is, in the band division filters 113-1 and 113-2, the phase difference between the audio
signals extracted for each band is approximately 0 degrees as indicated by the frequency phase
characteristic of FIG. 8.
Therefore, the correction filter 112 is configured to transmit the amplification units 114-1 and
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114-2, via the band division filters 113-1 and 113-2 in which the phase difference between the
audio signals becomes approximately 0 degrees for each of the extracted bands. It is an inverse
filter obtained based on an impulse response measured by collecting the sound signals output
from the speakers 115-1 and 115-2 by the microphone.
For this reason, the audio signal output from the speaker 115-1 in the high frequency band and
the audio signal output from the speaker 115-2 in the low frequency band are simultaneously
corrected by the correction filter 112 at a stage prior to the band division. As a result, it becomes
possible to obtain ideal frequency amplitude characteristics.
[0049]
As a result, since the frequency amplitude characteristic and the frequency phase characteristic
as the whole of the output unit 101 including the speakers 115-1 and 15-2 are improved, the
sound quality is improved in the wide band and the tone balance. It is possible to output the
voiced voice.
[0050]
In the above, as shown in FIG. 8, an example in which the phase difference between the audio
signals in all frequency bands of the band division filters 113-1 and 113-2 is substantially zero
has been described. It is sufficient if the phase difference of the audio signal in the frequency
band of the part is approximately zero.
That is, when it is desired to flatten the frequency band only around 200 Hz, as shown in the
upper part of FIG. 11, the waveform L121 indicating the phase of the first frequency band
divided and the phase of the second frequency band are indicated. As shown by the waveform
L122, the phase difference may be set to be approximately 0 degrees in the vicinity of 200 Hz.
Further, when it is desired to flatten the frequency band of only the band of 100 Hz or more, as
shown in the lower part of FIG. 11, waveform L131 indicating the phase of the first frequency
band and waveform L132 indicating the phase of the second frequency band. The phase
difference may be approximately 0 degrees in the range of 100 Hz or more, as shown in FIG.
[0051]
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14
Also, it is empirically understood that if the phase difference of the frequency phase
characteristic in the band division filter is in the range of about 0 degree to about 90 degree, the
frequency amplitude characteristic can be made substantially flat for the corresponding
frequency band. ing.
Furthermore, even if the phase difference of the frequency phase characteristic in the band
division filter is set to about 180 degrees, it is known that there may be cases where the
frequency amplitude characteristic can be made substantially flat for the corresponding
frequency band. There is.
In this case, it is known that if the phase difference of the frequency phase characteristics in the
band division filter is in the range of about 90 degrees to about 180 degrees, the frequency
amplitude characteristics can be made substantially flat even in the corresponding frequency
band. .
Therefore, the frequency amplitude characteristic may be made substantially flat by setting the
phase difference of the frequency phase characteristic in the band division filter to approximately
0 degrees or approximately 180 degrees.
[0052]
<2. First Modified Example> [Configuration Example of Output Unit Where Amplifier is
Provided at the Front Stage of Band Division Filter] In the above, the amplifier 114-1 is provided
at the rear stage of the band division filters 113-1 and 113-2. , 114-2 have been described, but
they may be provided in front of the band division filters 113-1 and 113-2.
[0053]
FIG. 12 shows a configuration example of the output unit 101 in which the amplification unit is
provided at the front stage of the band division filter. In FIG. 12, the same name and the same
reference numeral are attached to the configuration having the same function as the
configuration of FIG. 5, and the description thereof will be appropriately omitted. That is, the
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output unit 101 of FIG. 12 differs from the output unit 101 of FIG. 5 in that the amplification unit
121, instead of the band division filters 113-1 and 113-2 and the amplification units 114-1 and
114-2. And band division filters 122-1 and 122-2. Since the basic functions are the same, the
description thereof is omitted, but in the output unit 101 of FIG. 12, the amplification unit 121 is
provided in the front stage of the band division filters 122-1 and 122-2. Therefore, for example,
when the amplification unit 121 is an analog amplification unit including an analog-to-digital
conversion unit, the band division filters 122-1 and 122-2 need to be configured as analog filters.
[0054]
[Output Process by Output Unit of FIG. 12] Next, the output process by the output unit 101 of
FIG. 12 will be described with reference to the flowchart of FIG. The processes of steps S11 to
S13 and S16 in the flowchart of FIG. 13 are the same as the processes of steps S1 to S3 and S6
described with reference to the flowchart of FIG. That is, in FIG. 13, in steps S11 to S13, an audio
signal is acquired, analog-to-digital conversion is performed, and a correction filter is applied.
[0055]
Then, in step S14, the amplification unit 121 amplifies the audio signal including all the bands
and supplies the amplified signal to each of the band division filters 122-1 and 122-2.
[0056]
In step S15, the band division filters 122-1 and 122-2 divide the audio signal supplied from the
amplification unit 121 into each band, extract it, and extract the audio signal composed of the
extracted band signals. Are supplied to the speakers 115-1 and 115-2.
Thereby, in step S16, the speakers 115-1 and 115-2 output as sound.
[0057]
By the above processing, it is possible to obtain the same operation and effect as the output unit
101 of FIG. 1, and as a result, it is possible to improve the sound quality of the audio output.
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[0058]
<3.
Second Modified Example> [Configuration Example of Output Unit for Applying Loudspeaker
Simulated Filter to Band-Divided Audio Signal] In the above, it is possible to faithfully reproduce
the original sound by making the frequency amplitude characteristic flat. Although it has been
described that the sound quality is to be made, there is a preference for the sound quality, and
for example, there is also a case where it is not preferred to be flat. In such a case, the correction
filter 112 may be responded by adding a target frequency characteristic. In addition, a filter may
be provided to apply various speaker characteristics to the audio signal divided for each band by
the band division filter.
[0059]
FIG. 14 shows a configuration example of the output unit 101 provided with a filter for applying
various speaker characteristics to audio signals divided into bands by band division filters. In the
output unit 101 of FIG. 14, the components having the same functions as those of the output unit
101 of FIG. 5 have the same names and the same reference numerals, and the description thereof
will be omitted as appropriate. . That is, the output unit 101 of FIG. 14 differs from the output
unit 101 of FIG. 5 in that the speaker simulation filter 131 is disposed between the band division
filters 113-1 and 113-2 and the amplification units 114-1 and 114-2. -1, 131-2 are provided
respectively. The speaker simulated filters 131-1 and 131-2 are filters to which various speaker
characteristics are added, respectively. By this processing, do the speakers 115-1 and 115-2 have
the acoustic characteristics of various speakers? It is possible to output sound with a high sound
quality like.
[0060]
[Output Process by Output Unit of FIG. 14] Next, the output process by the output unit 101 of
FIG. 14 will be described with reference to the flowchart of FIG. The processes of steps S31 to
S34, S36, and S37 in the flowchart of FIG. 15 are the same as the processes of steps S1 to S6
described with reference to the flowchart of FIG. That is, in FIG. 13, in steps S31 to S34, an audio
signal is acquired, analog-to-digital conversion is performed, a correction filter is applied, and the
audio signal is divided for each band.
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[0061]
Then, in step S35, the speaker simulation filters 131-1 and 131-2 add the speaker characteristics
specified by the filters to the audio signals of the respective frequency bands, and the
amplification units 114-1 and 114-2 are added. Supply.
[0062]
Then, in steps S36 and S37, the signal is amplified and output from the speakers 115-1 and 1152.
[0063]
By the above-described processing, it is possible to obtain the same effects as those of the output
unit 101 of FIG. 1 and to add various speaker characteristics.
For this reason, for example, by applying the characteristic of a speaker called a master to the
speaker simulated filters 131-1 and 131-2, it becomes possible to reproduce an audio output
outputted by a speaker called a master.
As a result, it is possible to improve the sound quality of the audio output.
[0064]
<4. Third Modified Example> [Configuration Example of Output Unit for Applying Speaker
Simulated Filter to Audio Signal Including All Bands] In the above, an example of providing a
speaker simulated filter for adding a speaker characteristic to the subsequent stage of the band
division filter will be described. However, it may be provided in the previous stage of the band
division filter to apply the filtering process to the audio signal of the entire band.
[0065]
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FIG. 16 shows an output unit 101 in which a speaker simulation filter is provided in front of a
band division filter. The configuration having the same function as the output unit 101 in FIG. 5
in the output unit 101 in FIG. 16 is given the same name and the same reference numeral, and
the description thereof will be omitted as appropriate. That is, the output unit 101 of FIG. 16
differs from the output unit 101 of FIG. 5 in that a speaker simulation filter 151 is added
between the ADC 111 and the correction filter 112. Furthermore, the speaker characteristics
added by the speaker simulation filter 151 are set by the filter control unit 152. The filter control
unit 152 downloads the acoustic characteristics of various speakers stored in the speaker
simulation filter library 162 that can communicate with each other via the network 161, and sets
the acoustic characteristics in the speaker simulation filter 151. For this reason, it becomes
possible to switch and add the acoustic characteristic added by the speaker simulation filter 151
to various things.
[0066]
[Output Process by Output Unit of FIG. 16] Next, the output process by the output unit 101 of
FIG. 16 will be described with reference to the flowchart of FIG. The processes of steps S54, S55,
and S57 to S60 in the flowchart of FIG. 17 are the same as the processes of steps S1 to S6
described with reference to the flowchart of FIG.
[0067]
In step S51, the filter control unit 152 displays a list of downloadable and available speaker
simulation filters stored in the speaker simulation filter library 162 via the network 161 on a
display unit (not shown) or the like. And also displays an image prompting you to select one.
[0068]
In step S52, the filter control unit 152 determines whether the user operates the operation unit
(not shown) to select any one of the speaker simulated filters, and repeats the same process until
it is selected.
If it is determined in step S52 that, for example, one of the speaker simulated filters has been
selected, the process proceeds to step S53.
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[0069]
In step S53, the filter control unit 152 downloads data of the selected speaker simulated filter
among the data of the speaker simulated filter stored in the speaker simulated filter library 162
via the network 161. Then, the filter control unit 152 sets the downloaded data of the speaker
simulation filter in the speaker simulation filter 151.
[0070]
When audio signals are acquired and analog-to-digital converted by the processes of steps S54
and S55, the speaker simulation filter 151 is set to the speaker simulation filter 151 set by the
filter control unit 152 in step S56. By applying the filter processing as described above, acoustic
characteristics are added to the audio signal.
[0071]
In the processes of steps S57 to S60, the audio signal is subjected to a correction filter, divided
into bands, amplified for each band, and output as audio from the speakers 115-1 and 115-2.
[0072]
By the above process, it becomes possible to obtain the same function and effect as the output
unit 101 of FIG. 1, and it becomes possible to switch and add various speaker characteristics. By
switching and applying to the speaker simulation filter 151, it becomes possible to reproduce an
audio output as if a speaker called a master is switched.
As a result, it is possible to improve the sound quality of the audio output.
[0073]
<4.
Fourth Modified Example> [Configuration Example where Output Unit is Applied to Earphone] In
the above, an example in which the output unit 101 is configured as a speaker has been
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described. Because of the existence, the configuration of the output unit 101 described above
may be applied to the earphone. Furthermore, the effect of sound image localization may be
further enhanced by virtual reproduction with earphones or the like.
[0074]
FIG. 18 shows a configuration example for explaining an example in which the output unit 101 is
applied to the earphone 171 and virtual reproduction is realized using a head-related transfer
function (HRTF).
[0075]
As shown in the left part and the right part of FIG. 18, in the earphone 171, the parts used by the
left and right ears are configured by the output parts 101-1 and 101-2.
The audio output reproduced by the earphone 171 is, as shown in the left part of FIG. 18, the
speakers Lv, Cv, Rv in the order of left front, front front, right front as viewed from the user H
wearing the earphone 171. Create a state of virtually outputting voice. Furthermore, the speakers
Lv, Cv and Rv output so-called virtual voices to the user H as if virtual localization (sound image
localization) (not shown) other than the user H exists. Realize playback.
[0076]
More specifically, as shown in the right part of FIG. 18, the earphone 171 is configured by the
output units 101- and 101-2. In the right view of FIG. 18, the output unit 101-1 of the earphone
171 outputs the sound of the left channel L, and the output unit 101-2 outputs the sound of the
right channel R. Further, among the audio signals Lv, Cv and Rv having the speakers Lv, Cv and
Rv as sound sources, the audio signals reaching the left ear of the user H as the left channel L
have head transfer functions of FIG. When represented by the head related transfer functions LL,
CL, RL shown in the right part of FIG. 18 corresponding to the respective paths LL, CL, RL shown
in the left part, the voice signals Lv × LL, Cv ×, respectively. It becomes CL, Rv × RL. Similarly,
among the audio signals Lv, Cv and Rv using the speakers Lv, Cv and Rv as the sound sources,
the audio signals reaching the right ear of the user H as the right channel R have their head
related transfer functions as shown in FIG. When expressed by the head related transfer
functions LR, CR, RR shown in the right part of FIG. 18 corresponding to the respective paths LR,
CR, RR shown in the left part of FIG. X CR, Rv x RR.
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[0077]
The HRTFs 201 and 202 for HRTFs 201 and 202 shown in the right part of FIG. 18 perform
arithmetic processing defined by HR functions LL and LR on the audio signal Lv, and output units
101-1 respectively. , Supply to 101-2. Further, the head related transfer function processing
units HRTFs 203 and 204 perform arithmetic processing defined by the head related transfer
functions CL and CR on the audio signal Cv, and respectively supply them to the output units
101-1 and 101-2. Further, the head related transfer function processing units HRTFs 205 and
206 perform arithmetic processing defined by the head related transfer functions RL and RR on
the audio signal Rv, and respectively supply them to the output units 101-1 and 101-2.
[0078]
The adder 211-1 adds the audio signals Lv × LL, Cv × CL, and Rv × RL and adds them to an
output unit 101-1 that outputs an audio signal of the left channel L. Similarly, the adder 211-2
adds the audio signals Lv × LR, Cv × CR, and Rv × RR to combine them, and supplies the result
to the output unit 101-2 that outputs the audio signal of the right channel R.
[0079]
The output units 101-1 and 101-2 convert the audio signals using the speakers Lv, Cv, and Rv as
sound sources into high-quality sound through output processing including band division and
output the sound signals to the left and right ears. As a result, the user H can view the highquality sound while recognizing the sound field localization to be located outside the head based
on the sound output of the virtually configured speakers Lv, Cv, Rv. And virtual reproduction is
realized.
[0080]
[Virtual Reproduction Process] Next, virtual reproduction process by the earphone 171 of FIG. 18
will be described with reference to the flowchart of FIG.
[0081]
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In step S81, the head related transfer function processing units HRTFs 201 to 206 perform
arithmetic processing defined by the head related transfer functions LL, LR, CL, CR, RL, and RR
on the audio signals Lv, Cv, and Rv, It outputs to each adder 211-1 and 211-2.
[0082]
In step S82, the adder 211-1 adds the supplied audio signals Lv × LL, Cv × CL, and Rv × RL,
and outputs the result to the output unit 101-1.
Further, the adder 211-2 adds the supplied audio signals Lv × LR, Cv × CR, Rv × RR, and
outputs the result to the output unit 101-2.
[0083]
In step S 83, the output units 101-1 and 101-2 execute output processing based on the supplied
audio signals to convert the audio signals into high-quality sound and output it as audio.
The output process is the same as the process described with reference to the flowchart of FIG.
10, and thus the description thereof is omitted.
[0084]
By the above processing, the phase difference due to the frequency phase characteristic is made
approximately 0 degree or approximately 180 degree, the frequency amplitude characteristic as
a whole and the frequency phase characteristic are improved, and it is wide band and tone It is
possible to realize virtual reproduction with high-quality sound with excellent balance.
[0085]
Also, if the music is digitized on a CD (Compact Disk), the sampling rate is 44.1 kHz, and in the
case of recent DVD (Digital Versatile Disk) or Blu-ray Disk content, the sampling rate is 48 kHz
There are many.
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However, there are also high sampling rate 96 kHz and 192 kHz contents. As the sampling rate
increases, the filter length of the FIR becomes longer in order to obtain the low-pass correction
effect. In the case of simply going from 48 kHz to 96 kHz, a doubled filter length is necessary to
obtain almost the same effect. And, when reproducing a wide band of 192 kHz or more, more
speaker units may be used, and a speaker system of 3 way or more may appear. Given this
situation, the sampling rate is increased, and speaker units are increased, and this is subjected to
a band division filter as in the conventional case, and then the filter correction is performed for
each divided band, resulting in a huge amount of computation. It will be necessary. Therefore, as
described above, the band division filter is configured such that the phase difference between the
respective frequency phase characteristics is approximately 0 degrees or approximately 180
degrees, and only one correction filter is provided in front of the band division filter. With this, it
is possible to reduce operation resources.
[0086]
Furthermore, in the future, in a mobile device with a speaker (MP3 (MPEG Audio Layer-3) player,
mobile phone, notebook PC (Personal Computer), tablet PC, etc.), a wide band reproduction
environment can be obtained by combining different speaker units. Can be realized, and it is
possible to output high-quality sound even at that time.
[0087]
The above-described series of processes may be performed by hardware or software.
When the series of processes are performed by software, a program that configures the software
is installed on a computer. Here, the computer includes, for example, a general-purpose personal
computer that can execute various functions by installing a computer incorporated in dedicated
hardware and various programs.
[0088]
FIG. 20 is a block diagram showing an example of a hardware configuration of a computer that
executes the series of processes described above according to a program.
[0089]
In the computer, a central processing unit (CPU) 1001, a read only memory (ROM) 1002, and a
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random access memory (RAM) 1003 are mutually connected by a bus 1004.
[0090]
An input / output interface 1005 is further connected to the bus 1004.
An input unit 1006, an output unit 1007, a storage unit 1008, a communication unit 1009, and a
drive 1010 are connected to the input / output interface 1005.
[0091]
The input unit 1006 includes a keyboard, a mouse, a microphone and the like.
The output unit 1007 includes a display, a speaker, and the like. The storage unit 1008 includes
a hard disk, a non-volatile memory, and the like. The communication unit 1009 includes a
network interface or the like. The drive 1010 drives removable media 1011 such as a magnetic
disk, an optical disk, a magneto-optical disk, or a semiconductor memory.
[0092]
In the computer configured as described above, for example, the CPU 1001 loads the program
stored in the storage unit 1008 into the RAM 1003 via the input / output interface 1005 and the
bus 1004, and executes the program. Processing is performed.
[0093]
The program executed by the computer (CPU 1001) can be provided by being recorded on, for
example, a removable medium 1011 as a package medium or the like.
Also, the program can be provided via a wired or wireless transmission medium such as a local
area network, the Internet, or digital satellite broadcasting.
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[0094]
In the computer, the program can be installed in the storage unit 1008 via the input / output
interface 1005 by mounting the removable media 1011 in the drive 1010. The program can be
received by the communication unit 1009 via a wired or wireless transmission medium and
installed in the storage unit 1008. In addition, the program can be installed in advance in the
ROM 1002 or the storage unit 1008.
[0095]
Note that the program executed by the computer may be a program that performs processing in
chronological order according to the order described in this specification, in parallel, or when
necessary, such as when a call is made. It may be a program to be processed.
[0096]
Further, in the present specification, a system means a set of a plurality of components (devices,
modules (parts), etc.), and it does not matter whether all the components are in the same case.
Therefore, a plurality of devices housed in separate housings and connected via a network, and
one device housing a plurality of modules in one housing are all systems. .
[0097]
Note that the embodiments of the present technology are not limited to the above-described
embodiments, and various modifications can be made without departing from the scope of the
present technology.
[0098]
For example, the present technology can have a cloud computing configuration in which one
function is shared and processed by a plurality of devices via a network.
[0099]
Further, each step described in the above-described flowchart can be executed by one device or
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in a shared manner by a plurality of devices.
[0100]
Furthermore, in the case where a plurality of processes are included in one step, the plurality of
processes included in one step can be executed by being shared by a plurality of devices in
addition to being executed by one device.
[0101]
The present technology can be configured as follows.
(1) A plurality of speakers for outputting sound in each band, a correction filter for correcting an
audio signal including a plurality of bands according to the characteristics of the plurality of
speakers, and an audio signal corrected by the correction filter And a plurality of band division
filters that divide the band of the speaker so that the phase difference between the respective
phase characteristics is approximately 0 degrees or approximately 180 degrees, and the
correction filter is configured to pass through the plurality of band division filters. And an inverse
filter that is set by an impulse response based on audio output for each band from the plurality of
speakers.
(2) In the plurality of band division filters, the phase difference between the phase characteristics
of each of the audio signals corrected by the correction filter is about 0 degrees or about 180
degrees only for a predetermined frequency band. The sound processing apparatus according to
(2), wherein the sound processing apparatus is divided into the band of the speaker.
(3) The information processing apparatus further includes an amplification unit for amplifying
the audio signal, wherein the amplification unit is one amplification unit for amplifying the audio
signal before being divided by the band division filter, or The audio processing device according
to (1) or (2), which is a plurality of amplification units that respectively amplify the divided audio
signals of each band.
(4) The information processing apparatus further includes an additional filter for adding the
sound characteristic of another sound processing apparatus to the sound signal, and the sound
characteristic of the other sound processing apparatus is downloaded from a library connected
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by a network. The voice processing device according to any one of 3). (5) The additional filter is
one additional filter that adds acoustic characteristics of the other audio processing apparatus to
the audio signal before being divided by the band division filter, or is divided by the band division
filter The voice processing device according to (4), which is a plurality of additional filters for
adding the acoustic characteristics of the other voice processing device to each band. (6) The
input audio signal is a multi-channel audio signal, which is a composite of audio signals whose
sound images are localized by a head related transfer function, and any one of (1) to (5) An
earphone consisting of a voice processing device. (7) A voice processing method of a voice
processing apparatus including a plurality of speakers for outputting voice for each band, the
correction filter processing for correcting a voice signal including a plurality of bands according
to the characteristics of the plurality of speakers. A plurality of band division filter processings of
dividing the audio signal corrected by the correction filter processing into the band of the
speaker so that the phase difference of each phase characteristic becomes approximately 0
degree or approximately 180 degrees, The correction filter is an inverse filter that is set by an
impulse response based on a sound output for each band from the plurality of speakers via the
plurality of band division filters. (8) A computer for controlling an audio processing device
including a plurality of speakers for outputting audio in each band, a correction filter for
correcting an audio signal including a plurality of bands according to the characteristics of the
plurality of speakers, The audio signal corrected by the filter is caused to function as a plurality
of band division filters for dividing into bands of the speaker so that the phase difference of each
phase characteristic becomes approximately 0 degree or approximately 180 degrees, and the
correction filter is A reverse filter set by an impulse response based on voice output for each
band from the plurality of speakers via the plurality of band division filters. (9) A recording
medium on which the program described in (8) is recorded.
[0102]
DESCRIPTION OF SYMBOLS 101 output part, 111 ADC, 112 correction filter, 113-1, 113-2 band
division | segmentation filter, 114-1, 114-2 amplifier part, 115-1, 115-2 speaker, 121 amplifier
part, 122-1, 122 -2 band division filter, 131-1, 131-2, 151 speaker simulation filter, 161
network, 162 speaker simulation filter library, 201 to 206 head related transfer function TRTF
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