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JP2000148161

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DESCRIPTION JP2000148161
[0001]
The present invention relates to a sound source signal according to a noise signal, if there is an
unnecessary noise, in addition to a sound source signal to be reproduced, in a sound field such as
a passenger compartment, a listening room or a public space. The present invention relates to an
automatic sound quality control method and apparatus used to control frequency characteristics
and sound volume of
[0002]
2. Description of the Related Art Heretofore, as a control device of this type, there has been one
as disclosed in JP-A-10-178695. FIG. 8 shows a configuration example of a conventional
automatic tone volume control apparatus. In FIG. 8, 801 is a sensor for detecting ambient noise
such as a microphone, 802 is a source signal input terminal for music or voice, 803 is a sensor
signal frequency analysis means for frequency analysis of the sensor signal, 804 is frequency
analysis of the source signal Source signal frequency analysis means for performing the process,
noise signal calculation means for calculating the noise signal from the sensor signal analysis
result and the source signal analysis result, 806 is masking amount calculation means for
calculating the masking amount due to ambient noise of the source signal, Compensation amount
setting means for setting the frequency characteristic control amount and volume control
amount from the calculated masking amount, 808 is frequency characteristic control means for
controlling the frequency characteristic of the source signal such as an equalizer, 809 is control
the volume of the source signal such as a volume Volume control means 810 for emitting source
signals into space It is.
08-05-2019
1
[0003]
Next, the operation of the above conventional example will be described. In FIG. 8, the frequency
characteristic control means 808 such as an equalizer changes the frequency characteristic of a
source signal such as music or voice input to the source signal input terminal 802, and the
volume is adjusted by a volume control means 809 such as a volume. It is radiated into space by
the speaker 810. The signal input to the source signal input terminal 802 is also input to the
source signal frequency analysis means 804, where source signal levels of one or more
frequency bands are analyzed at fixed time intervals, the noise signal calculation means 805 and
the masking amount This is one input to the calculation means 806.
[0004]
The sensor 801 is, for example, a microphone, and is installed near the place where the sound
output by the speaker 810 is heard or in a place where the noise highly correlated with the
ambient noise can be detected in the space where the speaker 810 is installed. It will be done.
The sensor 801 may be a transmitting microphone in a telephone or the like. The sensor 801
may be a sensor other than a microphone such as an acceleration sensor that can detect a signal
highly correlated with ambient noise. A signal detected by the sensor 801 is analyzed at
predetermined time intervals by the sensor signal frequency analysis means 803 at signal levels
of one or more frequency bands, and becomes another input of the noise signal calculation
means 805. The signals detected by the sensor 801 include not only the ambient noise signal but
also the source signal output by the speaker 810. Therefore, the noise signal calculation means
805 weights the source signal analyzed by the source signal frequency analysis means 804 to
correct the source signal characteristics at the sensor position, and then the source signal is
analyzed by the sensor signal frequency analysis means 803 Only the noise signal is calculated
by subtracting the signal for each frequency band. The weighting of the source signal is
performed taking into consideration the transfer function from the speaker 810 to the sensor
801 and also the current control state, that is, the control amount of the frequency characteristic
control means 808 and the volume control means 809.
[0005]
The masking amount calculation means 806 uses the source signal level for each frequency band
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which is the output signal of the source signal frequency analysis means 804 and the noise
signal level for each frequency band which is the output signal of the noise signal calculation
means 805. The amount by which the source signal is masked by the noise signal is calculated at
fixed time intervals. Assuming that the source signal level is S and the noise signal level is N, the
masking amount M can be expressed by the following (Expression 1). M [dB] = a (S-N) 2 + b (S-N)
+ c (Equation 1) However, a, b and c are suitable constants.
[0006]
Masking is a phenomenon in which one sound becomes difficult to hear by another sound, and
the masking amount is necessary to make the sound so hard to hear in the original sound size.
Amount of gain. Therefore, if the gain of the source signal is increased by the masking amount
calculated by the masking amount calculating means 806 for each frequency band, reproduction
can be performed with the same sound size and sound quality as when there is no noise.
[0007]
The signals analyzed at fixed time intervals by the source signal frequency analysis means 804
and the noise signal calculation means 805 have large temporal fluctuations. Therefore, the
masking amount calculated by the masking amount calculating means 806 also greatly fluctuates
temporally. If the amount is used as the control amount of the frequency characteristic control
means 808 or the volume control means 809 as it is, the fluctuation amount in a short time
becomes too large to be unnaturally audible. Therefore, the compensation amount setting unit
807 uses the integration or averaging of the output signal of the masking amount calculation
unit 806, the LPF (Low Pass Filter), or the control amount of the frequency characteristic control
unit 808 or the volume control unit 809 by other methods. It is made to be updated smoothly,
and the source signal is changed naturally for auditory sense.
[0008]
As described above, even in the above-described conventional automatic sound volume control,
even if ambient noise exists, the frequency characteristics and volume of the source signal are
changed according to the characteristics of the detected source signal and the characteristics of
the ambient noise. Even if the characteristics of the noise change, it can be reproduced so that it
can be heard with the same loudness and sound quality as when there is no ambient noise.
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[0009]
However, in the above-described conventional automatic tone volume control apparatus, the
amount of computation is large and the hardware scale is large because the frequency analysis of
the source signal and the sensor signal in all frequency bands is performed. There was a problem
of
[0010]
The present invention is intended to solve such conventional problems, and an object thereof is
to provide an excellent automatic tone volume control method and apparatus with a small
amount of calculation and small hardware scale.
[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is
provided with sub-band dividing means and sub-band combining means, analyzes noise signals
and source signals, calculates control amounts, and controls source signals. Is performed after
division into sub-bands.
Therefore, according to the present invention, sub-band division and synthesis can be calculated
at high speed using a polyphase filter bank, and analysis of noise and source signals at low
sampling frequency after division into sub-bands, Since the control amount is calculated and the
source signal is controlled, it is possible to obtain an automatic tone volume control method and
apparatus with a small amount of calculation and a small hardware scale.
[0012]
The invention according to claim 1 of the present invention is to divide a noise signal and a
source signal into a plurality of frequency bands, lower a sampling frequency, and then perform
frequency analysis and control amount calculation processing. This is an automatic sound quality
control method characterized by small amount of calculation and an effect that the hardware
scale can be reduced.
[0013]
The invention according to claim 2 of the present invention is a sensor for detecting an ambient
noise, a sub-band dividing means for splitting a noise signal detected by the sensor into one or
more frequency bands, and a noise due to the ambient noise. Control amount calculating means
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for calculating at least one control amount of at least one of frequency characteristics and
volume for making it easy to hear the source signal, and controlling frequency characteristics
and / or volume of the source signal based on the calculated control amount An automatic sound
volume control apparatus comprising: at least one control means, and calculating the control
amount from the noise signal divided into the sub-bands and the input source signal, wherein the
control unit is divided into sub-bands. The frequency analysis of the noise signal can be
calculated at high speed to calculate the control amount from the noise signal and the input
source signal, and the hardware scale An effect that can be reduced.
[0014]
The invention according to claim 3 of the present invention is a sensor for detecting ambient
noise, sub-band splitting means for splitting a source signal into one or more frequency bands,
and easy to hear a source signal that is difficult to hear due to ambient noise. Control amount
calculating means for calculating at least one control amount of frequency characteristics and
sound volume, and at least one control means for controlling frequency characteristics and / or
sound volume of the source signal based on the calculated control amount An automatic sound
volume control apparatus characterized in that the control amount is calculated from a noise
signal detected by the sensor and a source signal divided into sub-bands, and the noise signal and
sub-band detected by the sensor Frequency analysis of the source signal can be calculated at
high speed to calculate the control amount from the source signal divided into An effect that
mimics the can be reduced.
[0015]
The invention according to claim 4 of the present invention comprises sub-band division means
for dividing a noise signal detected by a sensor into one or more frequency bands, and the
control from the noise signal and source signal divided into sub-bands. The automatic sound
volume control apparatus according to claim 3, characterized in that: the frequency analysis of
the noise signal and the source signal is performed to calculate the control amount from the
noise signal and the source signal divided into sub-bands. Can be calculated at high speed, and
the hardware scale can be reduced.
[0016]
The invention according to claim 5 of the present invention calculates a control amount of at
least one of a sensor for detecting ambient noise, and frequency characteristics and volume for
making it easy to hear a source signal that has become difficult to hear due to ambient noise. The
control amount calculating means, the sub-band dividing means for dividing the source signal
into one or more frequency bands, the sub-band combining means for synthesizing the source
signal divided into the sub-bands, and the calculated control amount And at least one control
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means for controlling the frequency characteristic and / or the volume of the source signal,
wherein the control amount is calculated from the noise signal detected by the sensor and the
source signal divided into subbands, and the subbands An automatic tone volume control
apparatus characterized by controlling frequency characteristics and / or volume using a source
signal divided into Analysis and control of the source signal to calculate the control amount from
the noise signal detected by and the source signal divided into subbands, and to control the
frequency characteristics or the volume using the source signal divided into subbands Can be
calculated at high speed, and the hardware scale can be reduced.
[0017]
The invention according to claim 6 of the present invention comprises sub-band division means
for dividing a noise signal detected by a sensor into one or more frequency bands, wherein the
noise signal and the source signal divided into the sub-bands The automatic sound volume
control apparatus according to claim 5, wherein the control amount is calculated, and the
frequency of the noise signal and the source signal is calculated to calculate the control amount
from the noise signal and the source signal divided into sub-bands. The analysis and control of
the source signal can be calculated at high speed, and the hardware scale can be reduced.
[0018]
The invention according to claim 7 of the present invention comprises one or more band pass
filters and one or more down sampling means instead of the subband dividing means for dividing
a noise signal into one or more frequency bands. 7. The automatic tone volume control apparatus
according to claim 2, wherein the frequency analysis of the noise signal and the source signal,
and the control of the source signal can be calculated at high speed. The effect is that the
hardware scale can be reduced.
[0019]
The invention according to claim 8 of the present invention comprises one or more band pass
filters and one or more down sampling means instead of the subband dividing means for dividing
the source signal into one or more frequency bands. The automatic sound volume control
apparatus according to claim 3, 4 or 5, characterized in that frequency analysis of noise signals
and source signals can be calculated at high speed, and the hardware scale can be reduced. Have
the effect.
[0020]
The invention according to claim 9 of the present invention calculates a control amount of at
least one of a sensor for detecting ambient noise, and a frequency characteristic and a volume for
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making it easy to hear a source signal that has become difficult to hear due to ambient noise.
Control amount calculating means, at least one control means for controlling the frequency
characteristic and / or volume of the source signal based on the calculated control amount, code
of information closely related to subband coding or amplitude frequency characteristics of the
signal And means for decoding the bit stream of the encoded source signal, the noise signal
detected by the sensor and the level or amplitude of each subband of the source contained in the
bit stream An automatic sound volume control apparatus characterized in that the control
amount is calculated from information, and a noise signal detected by a sensor In order to
calculate the amount of control from the level or amplitude information of each sub-band of the
source included in the bit stream and the bit stream, frequency analysis such as sub-band
analysis of the source signal is not necessary and the hardware scale can be reduced .
[0021]
The invention according to claim 10 of the present invention calculates a control amount of at
least one of a sensor for detecting an ambient noise and a frequency characteristic and a volume
for making it easy to hear a source signal that has become difficult to hear due to the ambient
noise. Control amount calculating means, at least one control means for controlling the frequency
characteristic and / or volume of the source signal based on the calculated control amount, code
of information closely related to subband coding or amplitude frequency characteristics of the
signal Calculating means for calculating the control amount from the noise signal detected by the
sensor and the sub-band signal decoded by the decoding means; Automatic sound volume control
device characterized in that the noise signal detected by the sensor and decoded by the decoder
In order to calculate the control amount from the subband signal has the effect of sub-band
analysis without the need for a source signal, the hardware scale can be reduced.
[0022]
The invention according to claim 11 of the present invention calculates a control amount of at
least one of a sensor for detecting ambient noise and a frequency characteristic and a volume for
making it easy to hear a source signal that has become difficult to hear due to ambient noise. The
sensor includes control amount calculating means, encoding means for encoding information
closely related to subband encoding or signal amplitude frequency characteristics, and decoding
means for decoding a bit stream of the encoded source signal, The control amount is calculated
from the noise signal detected by and the level or amplitude information of each sub-band of the
source included in the bit stream, and the level or amplitude information of each sub-band is
changed to change the frequency of the source signal. Automatic sound volume control
characterized by controlling characteristics and / or volume, and noise detected by a sensor To
control the frequency characteristics and / or volume of the source signal by calculating the
controlled variable from the level or amplitude information of each sub-band of the source
contained in the signal and the bit stream and changing the level or amplitude information of
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each sub-band In addition, the frequency analysis and control of the source signal can be
calculated at high speed, and the hardware scale can be reduced.
[0023]
The invention according to claim 12 of the present invention comprises sub-band division means
for dividing a noise signal detected by a sensor into one or more frequency bands, and the
control using the noise signal divided into the sub-bands. The automatic sound volume control
apparatus according to claim 9, 10, or 11, wherein the amount of noise is calculated to calculate
the amount of control using a noise signal divided into subbands. The frequency analysis of the
signal and the source signal and the control of the source signal can be calculated at high speed,
and the hardware scale can be reduced.
[0024]
The invention according to claim 13 of the present invention comprises one or more BPFs and
one or more downsampling means, instead of the sub-band dividing means for dividing a noise
signal into one or more frequency bands. 13. The automatic sound volume control apparatus
according to claim 12, characterized in that frequency analysis of noise signals and source
signals and control of source signals can be calculated at high speed, and the hardware scale can
be reduced.
[0025]
The invention according to claim 14 of the present invention is the automatic tone volume
control apparatus according to any one of claims 8 to 12, wherein the decoder deconstructs the
input bit stream into each information amount, and And inverse quantization / decoding means
for decoding each information amount, and subband synthesis means for synthesizing subband
signals, and high-speed computation of noise signal analysis, source signal analysis, and source
signal control And the hardware scale can be reduced.
[0026]
According to a fifteenth aspect of the present invention, in the decoding means, a frame
decomposition processing means for decomposing an input bit stream into each information
amount, an inverse quantization decoding processing means for decoding each information
amount, and a subband The automatic tone volume control apparatus according to any one of
claims 9 to 13, comprising subband combining means for combining signals, wherein calculation
of noise signals, analysis of source signals and control of source signals are performed at high
speed. And the hardware scale can be reduced.
08-05-2019
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[0027]
In the invention according to claim 16 of the present invention, the control amount calculating
means comprises: a sensor signal analyzing means for analyzing a signal detected by the sensor;
a source signal analyzing means for analyzing a source signal; Noise signal calculation means for
calculating the noise signal by subtracting the signal analysis result, masking amount calculation
means for calculating the masking amount of the source due to noise using the noise signal and
the sensor signal, Smoothly from the calculated masking amount The automatic sound volume
control apparatus according to any one of claims 2 to 14, further comprising compensation
amount setting means for setting a control characteristic for updating the frequency
characteristic and / or the volume control amount. The frequency analysis and control of the
source signal can be calculated at high speed, and the hardware scale can be reduced.
[0028]
The invention according to claim 17 of the present invention is an audio apparatus including the
automatic tone volume control apparatus according to any one of claims 2 to 16, wherein
frequency analysis of noise signals and source signals and control of source signals are
performed. Can be calculated at high speed, and the hardware scale can be reduced.
[0029]
The invention according to claim 18 of the present invention is a communication terminal
apparatus including the automatic tone volume control apparatus according to any one of claims
2 to 16, which comprises: frequency analysis of noise signals and source signals; The control can
be calculated at high speed, and the hardware scale can be reduced.
[0030]
The invention according to a nineteenth aspect of the present invention is an information
terminal apparatus including the automatic sound quality control apparatus according to any one
of the second to sixteenth aspects, wherein high-speed frequency analysis of noise signals and
source signals and control of source signals are provided. It has the effect that it can be
calculated and the hardware scale can be reduced.
[0031]
The invention according to claim 20 of the present invention is an automatic sound quality
control apparatus in which processing means other than the sensors in the automatic sound
quality control apparatus according to claims 2 to 16 are realized by software, noise signal and
source It has the effect that the analysis of the signal and the control of the source signal can be
08-05-2019
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calculated at high speed.
[0032]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to
7.
(First Embodiment) FIG. 1 is a block diagram showing the configuration of the first embodiment
of the present invention, and 101 is a sensor such as a microphone or an acceleration sensor for
detecting a signal highly correlated with ambient noise or ambient noise; Is a source signal input
terminal such as music and voice; 103 is a subband dividing means for dividing a sensor input
signal into a plurality of subband signals; 104 is a subband dividing means for dividing a source
signal into a plurality of subband signals; Control amount calculation means for calculating the
control amount of the source signal from the sensor input signal and the source signal, 106 is a
sensor signal analysis means for analyzing the sensor signal divided into subbands, and 107 is a
source signal divided into subbands Source signal analysis means for analyzing, noise signal
calculation means for calculating noise signal from sensor signal analysis result and source signal
analysis result, 1 9 is a masking amount calculation means for calculating a masking amount due
to ambient noise of the source signal, 110 is a compensation amount setting means for
calculating and setting a frequency characteristic control amount and a volume control amount
of the source signal from the calculated masking amount Frequency characteristic control means
for controlling the frequency characteristic of the signal, 112 is a subband combining means for
combining the source signal divided into a plurality of subbands, 113 is volume control means
for controlling the volume of the source signal, 114 is a source signal It is a speaker that radiates
into space.
[0033]
Next, the operation of the first embodiment will be described.
In FIG. 1, a source signal such as music or voice input to a source signal input terminal 102 is
divided into a plurality of sub-band signals by the sub-band dividing means 104.
The source signal divided into sub-bands has its frequency characteristic and volume changed for
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each sub-band by the frequency characteristic control means 111 such as the equalizer and
volume for each sub-band, and is synthesized by the sub-band synthesis means 112.
The synthesized source signal is adjusted in overall volume by volume control means 113 such
as a volume, and is emitted to space by the speaker 114 to reach the listener.
The source signal divided into a plurality of sub-bands by the sub-band dividing means 104 is
also input to the source signal analysis means 107, and the level or all-pass level in each subband is calculated at fixed time intervals. It becomes one input of the masking amount calculation
means 109.
[0034]
A sensor 101 for detecting ambient noise such as a microphone is installed near the place where
the sound output by the speaker 114 is heard or where noise that is highly correlated with the
ambient noise at the listening place can be detected.
The sensor 101 may be a transmitting microphone in a communication terminal such as a
telephone set or a video conference system, or a speed sensor or an acceleration sensor highly
correlated with noise in a mobile room such as a car or a train.
The signal input to the sensor 101 is divided into a plurality of sub-band signals by the sub-band
dividing means 103, and the signal level or all-pass level in each sub-band is calculated at
predetermined time intervals by the sensor signal analysis means 106, noise signal calculation It
becomes another input of the means 108.
The noise signal calculation method by the noise signal calculation means 108, the masking
amount calculation method by the masking amount calculation means 109, and the
compensation amount setting method by the compensation amount setting means 110 are the
same as those in the conventional example.
[0035]
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11
The subband dividing means 103 and 104 and the subband synthesizing means 112 use the
polyphase filter bank to perform subband processing at high speed by a high-speed operation
method using DFT (Discrete Fourie Transform) or DCT (Discrete Cosine Transform). Analysis and
synthesis can be performed.
In addition, since the signal divided into the sub-bands has a sampling frequency lower than the
sampling frequency of the input signal, the time that can be applied to the processing of the
control amount calculating means 105 and the frequency characteristic control means 111
becomes long. The amount of computation per sample data can be small.
[0036]
As described above, according to the first embodiment, the noise signal and the source signal are
divided into subband signals by subband division processing using high-speed algorithm, and
then analysis, control amount calculation, and control processing are performed. This has the
effect that the amount of computation can be reduced and the hardware scale can be reduced.
[0037]
(Second Embodiment) FIG. 2 is a block diagram showing the configuration of the second
embodiment of the present invention. 201 is a sensor such as a microphone or an acceleration
sensor for detecting a signal highly correlated with ambient noise or ambient noise, 202 Is a
source signal input terminal for music or voice, 203 is a band pass filter (hereinafter referred to
as BPF) for dividing a sensor input signal into a plurality of frequency band signals, 204 is a BPF
for dividing a source signal into a plurality of frequency band signals, 205 is a downsampling
means for reducing the sampling frequency of the sensor signal divided into a plurality of
frequency bands, 206 is a downsampling means for lowering the sampling frequency of the
source signal divided into a plurality of frequency bands, 207 is a sensor input signal and the
source signal Control amount calculation means for calculating the control amount of the source
signal from the Sensor signal analysis means for analyzing the sensor signal divided into two,
source signal analysis means for analyzing the source signal divided into a plurality of frequency
bands, 210 noise signal from the sensor signal analysis result and the source signal analysis
result Noise signal calculating means for calculating the noise amount; 211 masking amount
calculating means for calculating the masking amount due to ambient noise of the source signal;
and 212 calculating and setting the frequency characteristic control amount and volume control
amount of the source signal from the calculated masking amount Compensation amount setting
means, frequency characteristic control means 213 for controlling the frequency characteristics
of the source signal, volume control means 214 for controlling the volume of the source signal,
and a speaker 215 for radiating the source signal into space.
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[0038]
Next, the operation of the second embodiment will be described.
In FIG. 2, the source signal input to the source signal input terminal 202 is divided into a
plurality of frequency band signals by the BPF 204, and the sampling frequency is lowered by
the downsampling unit 206.
The source signal which is the output signal of the downsampling means 206 is input to the
source signal analysis means 209, and the level or all-pass level in each frequency band is
calculated at predetermined time intervals.
Similarly, the signal input to the sensor 201 is divided into a plurality of frequency band signals
by the BPF 203, and the sampling frequency is lowered by the downsampling unit 205.
A sensor signal which is an output signal of the downsampling unit 205 is input to the sensor
signal analysis unit 208, and a level or an all-pass level in each frequency band is calculated at
predetermined time intervals.
The operations of the noise signal calculation means 210, the masking amount calculation means
211, the compensation amount setting means 212, the frequency characteristic control means
213, the volume control means 214 and the speaker 215 are the same as those of the abovedescribed conventional example.
[0039]
The sampling frequency lowered by the downsampling units 205 and 206 may be twice the
frequency of each bandwidth set by the BPFs 203 and 204.
Therefore, in the case of dividing into two equal frequency intervals by the BPFs 203 and 204,
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the sampling frequency may be 1/2 of the sampling frequency of the input.
[0040]
Also in the second embodiment, as in the first embodiment, the process of the control amount
calculating means 207 may be performed at a sampling frequency lower than the sampling
frequency of the input signal, and the amount of calculation can be small. .
[0041]
As described above, according to the second embodiment, since the noise signal and the source
signal are divided into a plurality of frequency bands, and the sampling frequency is lowered,
analysis and control amount calculation processing are performed, thereby reducing the amount
of calculation. It has the effect of being able to reduce the hardware scale.
[0042]
(Third Embodiment) FIG. 3 is a block diagram showing the configuration of the third embodiment
of the present invention. Reference numeral 301 denotes a sensor such as a microphone or an
acceleration sensor for detecting a signal highly correlated with ambient noise or ambient noise;
Is a bitstream input terminal of a source signal encoded by an encoder that encodes subband
information or information closely related to the amplitude frequency characteristic of the signal,
and 303 divides the sensor input signal into a plurality of subband signals Subband dividing
means, 304 is a control amount calculating means for calculating a control amount of a source
signal from a sensor input signal and a source signal, 305 is a sensor signal analyzing means for
analyzing a sensor signal divided into sub bands, 306 is a sensor signal Noise signal calculation
to calculate the noise signal from the analysis results and information highly correlated with the
level of each sub-band signal in the input bit stream Means 307 is a masking amount calculation
means for calculating a masking amount due to ambient noise of the source signal, 308 is a
compensation amount setting means for calculating and setting a frequency characteristic
control amount and a volume control amount of the source signal from the calculated masking
amount Is a decoder for decoding the input bit stream, 310 is a frame decomposition processing
means for decomposing the frame of the input bit stream and extracting each amount of
information, and 311 is an inverse quantum for decoding the sub-band signal according to each
information extracted Decoding / decoding means 312, subband combining means for combining
subband signals, 313 is frequency characteristic control means for controlling the frequency
characteristics of the source signal, 314 is volume control means for controlling the volume of
the source signal, and 315 is source signal Is a speaker that radiates into space.
[0043]
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FIG. 4 is a block diagram showing the configuration of the sub-band encoder, in which 401 is an
audio sample input terminal, 402 is an encoder, 403 is sub-band division processing means for
dividing an input signal into a plurality of sub-band signals, 404 Is a psychoacoustic model that
models psychoacoustic signal processing by masking the input signal itself, 405 is quantization
encoding processing means for encoding sub-band signals using the psychoacoustic model, 406
is encoding The frame formation processing means converts the received information into a bit
stream, and 407 is a bit stream output terminal.
FIG. 5 is a data structure diagram showing an example of a frame configuration in subband
coding.
[0044]
Next, the operation of the third embodiment will be described with reference to FIG. 3, FIG. 4 and
FIG.
First, subband coding processing will be described.
As shown in FIG. 5, in subband coding, a frame includes a header unit having information such as
sampling frequency and bit rate, a bit assignment information unit indicating the number of bits
allocated to each subband, and a signal in each subband It comprises a scale factor portion
indicating the maximum value, a sub-band sample portion indicating the signal of each sub-band,
and an ancillary data portion which is a spare bit.
A plurality of these frames are gathered to form a bit stream.
[0045]
In FIG. 4, the audio signal input from the audio sample input terminal 401 is divided by the subband division processing means 403 into a plurality of sub-band signals.
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The quantization coding processing means 405 uses the psycho-acoustic model 404 to code the
sub-band signal divided by the sub-band division processing means 403 into each information of
bit allocation information, scale factor and sub-band sample.
The psycho-acoustic model 404 is a model of auditory signal processing such as a phenomenon
in which the signal masks the signal itself and a minimum audible level, and is used for
compression of quantization information.
The frame formation processing means 406 adds a header part etc. to the encoded information
to form a frame, and the formed frame information is outputted from the bit stream output
terminal 407 as a bit stream.
[0046]
Next, the operation of the third embodiment will be described using FIG.
In FIG. 3, the bit stream formed as described above is input to a bit stream input terminal 302.
The input bit stream is decomposed by the frame decomposition processing unit 310 into pieces
of information such as scale factor, bit allocation information, and subband samples.
The decomposed information is decoded into a subband signal by the inverse quantization
decoding processing unit 311 and synthesized into an audio signal by the subband synthesis unit
312.
The synthesized signal is input to the frequency characteristic control means 313.
The scale factor decomposed by the frame decomposition processing unit 310 is input to the
noise signal calculation unit 306 and the masking amount calculation unit 307 as an analysis
result of each sub-band level of the source signal. The input to the noise signal calculation unit
306 and the masking amount calculation unit 307 may be information that is not correlated with
08-05-2019
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the signal level of each sub-band, even if it is not a scale factor. When information such as scale
factor indicates information indicating the maximum value of the signal of each sub-band is
converted to information indicating the average value of each sub-band signal, noise signal
calculation means 306 and calculation of masking amount It may be input to the means 307. The
operations of the sensor 301, subband dividing means 303, sensor signal analyzing means 305,
noise signal calculating means 306, masking amount calculating means 307, compensation
amount setting means 307, frequency characteristic control means 313, volume control means
314 and speaker 315 are as follows. This is the same as the conventional example or the first
embodiment.
[0047]
As described above, according to the third embodiment, the noise signal is divided into subband
signals by subband division processing using high-speed algorithm and then analyzed, and the
source signal is encoded by the encoding unit. Since the source information is not required to
analyze the source signal, the amount of computation can be reduced and the hardware scale can
be reduced.
[0048]
(Fourth Embodiment) FIG. 6 is a block diagram showing the configuration of the fourth
embodiment of the present invention. 601 is a sensor such as a microphone or an acceleration
sensor for detecting ambient noise or a signal highly correlated with ambient noise, 602 Is a
bitstream input terminal of a source signal encoded by an encoder that encodes subband
information or information closely related to the amplitude frequency characteristic of the signal,
and 603 divides the sensor input signal into a plurality of subband signals Subband dividing
means, 604 is a control amount calculating means for calculating the control amount of the
source signal from the sensor input signal and the source signal, 605 is a sensor signal analyzing
means for analyzing the sensor signal divided into sub bands, and 606 is a source Source signal
analysis means for analyzing subband signals, 607 calculates noise signal from sensor signal
analysis result and source signal analysis result Sound signal calculating means, 608 is masking
amount calculating means for calculating masking amount by ambient noise of source signal,
609 is compensation amount setting for calculating and setting frequency characteristic control
amount and volume control amount of source signal from calculated masking amount Means:
610 is a decoder for decoding the input bit stream; 611 is a frame decomposition processing
means for decomposing the frame of the input bit stream and extracting each amount of
information; 612 is a subband signal according to each information extracted Dequantization /
decoding means for decoding, 613 for subband synthesis means for synthesizing subband
signals, 614 for frequency characteristic control means for controlling the frequency
characteristics of the source signal, 615 for volume control means for controlling the volume of
the source signal, 616 is a speaker for radiating the source signal into space.
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[0049]
Next, the operation of the fourth embodiment will be described.
In FIG. 4, the bit stream input to the bit stream input terminal 302 in the same manner as in the
third embodiment is subjected to frame decomposition by frame decomposition processing
means 611, inverse quantization decoding processing means 612, and subband synthesis means
613. , Sub-band signal generation, and synthesis are performed.
The source signal decoded into the sub-band signal by the inverse quantization decoding
processing means 612 is input to the source signal analysis means 606, and the signal level of
each sub-band is analyzed by the source signal analysis means 606 at regular time intervals. The
source signal analyzed by the source signal analysis means 606 is input to the noise signal
calculation means 607 and the masking amount calculation means 608. The operations of the
sensor 601, subband dividing means 603, sensor signal analyzing means 605, noise signal
calculating means 607, masking amount calculating means 608, compensation amount setting
means 609, frequency characteristic control means 614, volume control means 615 and speaker
616 are as follows. This embodiment is the same as the above-described conventional
embodiment or the above-described first embodiment.
[0050]
As described above, according to the fourth embodiment, the noise signal is divided into subband
signals by subband division processing using high-speed algorithm and then analyzed, and the
source signal is decoded by the decoder. Since the sub-band signals are used, the amount of
computation can be reduced and the hardware scale can be reduced.
[0051]
(Fifth Embodiment) FIG. 7 is a block diagram showing the configuration of the fifth embodiment
of the present invention, and 701 is a sensor such as a microphone or an acceleration sensor for
detecting a signal highly correlated with ambient noise or ambient noise, 702 Is a bitstream input
terminal of a source signal encoded by an encoder that encodes subband information or
information closely related to the amplitude frequency characteristic of the signal, and 703
divides the sensor input signal into a plurality of subband signals Subband division means, 704 is
a control amount calculation means for calculating the control amount of the source signal from
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the sensor input signal and the source signal, 705 is a sensor signal analysis means for analyzing
the sensor signal divided into sub bands, and 706 is a sensor signal Noise signal calculation to
calculate the noise signal from the analysis results and information highly correlated with the
level of each sub-band signal in the input bit stream Means 707 is a masking amount calculation
means for calculating a masking amount due to ambient noise of the source signal, 708 is a
compensation amount setting means for calculating and setting a frequency characteristic
control amount or a volume control amount of the source signal from the calculated masking
amount Is a decoder for decoding the input bit stream, 710 is a frame decomposition processing
means for decomposing the frame of the input bit stream and extracting each amount of
information, and 711 is an inverse quantum for decoding the sub-band signal according to each
information extracted The decoding processing means, sub-band combining means 712 for
combining sub-band signals, 713 is an amplifier for amplifying the source signal, and 714 is a
speaker for radiating the source signal into space.
[0052]
Next, the operation of the fifth embodiment will be described.
In FIG. 7, the bit stream input to the bit stream input terminal 702 in the same manner as in the
third embodiment is subjected to frame decomposition by frame decomposition processing
means 710, inverse quantization decoding processing means 711, and subband synthesis means
712. , Sub-band signal generation, and synthesis are performed.
Information highly correlated with the in-frame level of the source subband signal such as scale
factor decomposed by the frame decomposition processing unit 710 is noise signal calculation
unit 706 and masking amount calculation as an analysis result of each subband level of the
source signal The information is input to the means 707. The operations of the sensor 701, the
subband dividing means 703, the sensor signal analyzing means 705, the noise signal calculating
means 706 and the masking amount calculating means 707 are the same as those of the abovementioned conventional embodiment or the above-mentioned first embodiment. Although the
compensation amount setting means 708 also allows the control amount to be updated smoothly
using the output signal of the masking amount calculation means 707 as in the above-described
conventional embodiment, the compensation amount setting means 708 is a scale factor, etc.
Change information that is highly correlated with the intraframe level of the source subband
signal. That is, the scale factor for each sub-band is made larger or smaller by the control amount
smoothed by the compensation amount setting means 708. Or, change the scale factor to all
subbands uniformly. Information having high correlation with the intra-frame level of the source
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sub-band signal such as the scale factor changed by the compensation amount setting means
708 is input to the inverse quantization decoding process means 711. The audio synthesized by
the subband synthesis means 712 is amplified by the amplifier 713 and radiated into space by
the speaker 714.
[0053]
As described above, according to the fifth embodiment, the noise signal is divided into subband
signals by subband division processing using high-speed algorithm and then analyzed, and the
source signal is encoded by the encoding unit. The use of encoded information eliminates the
need for analysis processing of the source signal, and the control of the source signal also utilizes
encoded information, so that the amount of computation can be reduced and the hardware scale
can be reduced. Have.
[0054]
In each of the above embodiments, both of the frequency characteristic and the volume are used
as the control amount to be calculated, and both of the frequency characteristic control unit and
the volume control unit are used as the control unit. It may be alone.
[0055]
As described above, according to the present invention, there is an effect that the amount of
calculation can be reduced because the signal is divided into sub-band signals by sub-band
division processing using a high-speed algorithm.
In addition, since the processing of noise and source signal analysis, control amount calculation,
and source signal control is performed using the signal whose sampling frequency is lowered, the
amount of calculation can be reduced.
In addition, in the case of including coding means for coding information closely related to the
amplitude frequency characteristic of the signal such as subband coding, and decoding means for
decoding a bit stream of the coded source signal, In order to analyze and control the source
signal using the signal level information of each of the sub-bands, the amount of computation can
be reduced. As a result, the hardware can be made smaller.
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