JP5663112B1 - Sound signal processing apparatus and hearing aid using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound signal processing device capable of stably suppressing wind noise and a hearing aid using the same. Converters 31R and 31L convert sound signals output from a pair of microphones 10R and 10L into sound component signals for each frequency band. The calculation unit calculates a phase difference between one sound component signal and the other sound component signal for each frequency band for the sound component signal on the low frequency side, and one sound component signal for the sound component signal on the high frequency side. A sound pressure difference with the other sound component signal is calculated for each frequency band. The memory 40 stores a phase difference and an upper limit value and a lower limit value of a sound pressure difference when sound is input from a point sound source for each frequency band. The determination unit 33 counts the number of frequency bands in which the ratio of the phase difference and sound pressure difference obtained by the calculation unit to the phase difference and sound pressure difference stored in the memory is greater than a predetermined value. When the counted value is larger than the predetermined value, the filter unit 34 performs a filtering process on the sound component signal in the counted frequency band. [Selection] Figure 1

Description

  The present invention relates to a sound signal processing apparatus, and is particularly suitable for suppressing wind noise.

  As a hearing aid, a device that processes a sound signal input from a microphone to reduce wind noise is known. A technique for determining the presence or absence of wind noise based on the magnitude of a component of a predetermined frequency of an input sound signal is known. Further, in Patent Document 1 below, there is a technique that utilizes a high correlation between auditory sounds such as speech input to two microphones, but a low correlation between wind noises input to two microphones. It is disclosed. Specifically, filtering is performed for each frequency band using a least mean square algorithm or the like.

Special table 2012-533244 gazette

  In the sound signal processing described in Patent Document 1, a sound signal is processed using the same method for each frequency band. However, it was found that the wind noise can be suppressed more stably by using different methods depending on the frequency band.

  Therefore, an object of the present invention is to provide a sound signal processing apparatus capable of stably suppressing wind noise and a hearing aid using the sound signal processing apparatus.

The sound signal processing device of the present invention includes a conversion unit, a calculation unit, a memory, a determination unit, and a filter unit.
The conversion unit converts each sound signal output from the pair of microphones into a sound component signal decomposed for each predetermined frequency band.
The calculation unit calculates a phase difference between a sound component signal based on the sound signal from one microphone and a sound component signal based on the sound signal from the other microphone for a sound component signal lower than a specific frequency at a predetermined frequency. Calculate for each band. Further, the calculation unit calculates a sound pressure difference between a sound component signal based on the sound signal from one microphone and a sound component signal based on the sound signal from the other microphone for a sound component signal on a higher frequency side than a specific frequency. Calculate for each frequency band.
In the memory, when the sound from the point sound source is input to the pair of microphones, the upper limit value and the lower limit value of the phase difference based on the sound from the point sound source have a predetermined frequency band on the lower frequency side than the specific frequency. It is memorized every time. In addition, the upper limit value and the lower limit value of the sound pressure difference based on the sound from the point sound source are previously stored in the memory for each predetermined frequency band on the higher frequency side than the specific frequency.
The determination unit is closer to the phase difference obtained by the calculation unit among the phase difference obtained by the calculation unit and the upper limit value and lower limit value of the phase difference stored in the memory on the lower frequency side than the specific frequency. And the number of frequency bands in which this ratio is greater than the first predetermined value is counted. Further, the determination unit is closer to the sound pressure difference obtained by the calculation unit between the sound pressure difference obtained by the calculation unit and the upper limit value and lower limit value of the sound pressure difference stored in the memory on the higher frequency side than the specific frequency. And the number of frequency bands in which this ratio is greater than the second predetermined value is counted.
When the number of frequency bands counted by the determination unit is larger than the third predetermined value, the filter unit performs a filtering process on the sound component signal of at least the frequency band counted by the determination unit.

  It has been found that the phase difference and the sound pressure difference for each frequency of sound emitted from a point sound source such as voice and input to a pair of microphones have the characteristics shown in FIGS. 2 and 3 with respect to the horizontal angle. Further, it was found that the absolute value of the phase difference and sound pressure difference for each frequency of wind noise input to the pair of microphones is sufficiently larger than the phase difference and sound pressure difference of the sound emitted by the point sound source. By utilizing this fact, it becomes possible to detect wind noise with high accuracy. Therefore, in the present invention, as described above, the determination unit is configured to input the phase difference and sound pressure difference of the input sound based on the database of the upper and lower limit values of the phase difference and the sound pressure difference for each frequency band in the case of a point sound source. Compared with, a frequency band in which wind noise is dominant can be extracted. By determining the wind noise in this way, it is possible to easily detect the wind noise and effectively suppress the wind noise. Note that a filter gain for suppressing wind noise may be determined based on the magnitude of the ratio between the phase difference / sound pressure difference in the database and the phase difference / sound pressure difference of the input sound.

  Moreover, the phase difference between the sound component signals based on the sound signals input to the pair of microphones is calculated on the lower frequency side than the specific frequency. Since the wavelength of the sound is long on the low frequency side, the phase difference of the sound input to the pair of microphones is difficult to be more than ± π radians. Therefore, by using the phase difference on the low frequency side, it is possible to stably extract the frequency band in which the wind noise is dominant. Further, on the higher frequency side than the specific frequency, the sound pressure difference of the sound component signal based on the sound signal input to the pair of microphones is calculated. Since the diffraction of sound is small on the high frequency side, it is easy to produce a sound pressure difference between sounds input to each microphone. Therefore, by using the sound pressure difference on the high frequency side, it is possible to stably extract a frequency band in which wind noise is dominant. Thus, in the sound signal processing device of the present invention, the frequency band to be filtered is calculated based on the phase difference or the sound pressure difference in accordance with the frequency band, so that wind noise can be effectively suppressed.

  Moreover, the hearing aid of the present invention includes the above-described sound signal processing device, and a pair of microphones are attached to the left and right ears.

  Since such a hearing aid can stably suppress wind noise in the sound signal processing device, it can be used satisfactorily even in windy environments.

  As described above, according to the present invention, a sound signal processing device capable of stably suppressing wind noise and a hearing aid using the sound signal processing device are provided.

It is a block diagram which shows the hearing aid which concerns on embodiment of this invention. It is the figure which graphed the phase difference information for every frequency of the sound input into a pair of microphone from the point sound source in the low frequency side from a specific frequency. It is the figure which graphed the sound pressure difference information for every frequency of the sound input into a pair of microphone from the point sound source in the high frequency side from a specific frequency. It is a figure which shows the sound signal input into DSP of FIG. 1 in simulation. It is a figure which shows a mode that the wind noise was removed in FIG. 4, and only the audio | voice signal was extracted. It is a figure which shows the audio | voice signal output from DSP as a result of simulation.

  Hereinafter, preferred embodiments of a sound signal processing apparatus according to the present invention and a hearing aid using the same will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a pocket type earphone in which earphones with microphones are attached to both ears. As shown in FIG. 1, the hearing aid of the present embodiment includes a pair of microphones 10R, 10L, a pair of A / D (analog / digital) converters 20R, 20L, a DSP (Digital Signal Processor) 30, and a DSP 30. , A pair of D / A (digital / analog) converters 50R and 50L, and a pair of earphones 60R and 60L. In the present embodiment, the DSP 30 and the memory 40 constitute an audio signal processing device, and the DSP 30 includes a pair of conversion units 31R and 31L, a calculation unit 32, a determination unit 33, a filter unit 34, and hearing aid processing. A unit 35 and a pair of inverse conversion units 36R and 36L are provided.

  Each of the microphones 10R and 10L outputs a sound signal corresponding to the input sound. Although not particularly illustrated, one microphone 10R and earphone 60R are provided in a housing attached to the right ear, and the other microphone 10L and earphone 60L are provided in a housing attached to the left ear. ing. The earphone portion with microphone and the main body portion in which the audio signal processing device is housed may be connected by wireless communication. In the case of an ear-hearing type hearing aid, the sound signal processing device may be provided on one side of the hearing aid, and the hearing aids may be connected to each other by wireless communication. When wireless communication is used, a transmission / reception unit (not shown) is provided.

  The sound signal from the microphone 10R input to the A / D converter 20R and the sound signal from the microphone 10L input to the A / D converter 20L are converted from analog signals to digital signals and output. The sound signal of the digital signal output from the A / D converters 20R and 20L is input to the DSP 30.

  The converting unit 31R decomposes the sound signal from the A / D converter 20R input to the DSP 30 into sound component signals for each predetermined frequency band using fast Fourier transform (FFT), and the converting unit 31L inputs to the DSP 30. The sound signal from the A / D converter 20L is decomposed into sound component signals for each predetermined frequency band using fast Fourier transform. Accordingly, a sound component signal based on the sound signal from the microphone 10R decomposed for each predetermined frequency band is output from the converter 31R, and the sound from the microphone 10L decomposed for each predetermined frequency band is output from the converter 31L. A sound component signal based on the signal is output. Note that the conversion unit 31R and the conversion unit 31L decompose the sound signal into sound component signals in the same frequency band.

  The calculation unit 32 performs the following calculation using the sound component signals of the respective frequency bands output from the conversion unit 31R and the conversion unit 31L. That is, the calculation unit 32 calculates the phase difference between the sound component signal from one conversion unit 31R and the sound component signal from the other conversion unit 31L for the sound component signal on the lower frequency side than the specific frequency. Further, the calculation unit 32 calculates the sound pressure difference between the sound component signal from one conversion unit 31R and the sound component signal from the other conversion unit 31L for a sound component signal on the higher frequency side than the specific frequency. The calculation of the phase difference and the sound pressure difference is performed for each predetermined frequency band. The specific frequency can be set as appropriate depending on the distance between the pair of microphones 10R and 10L, and is preferably a frequency at which the phase difference does not exceed ± π radians. When one microphone 10R is attached to the user's right ear and the other microphone 10L is attached to the user's left ear as in the present embodiment, the specific frequency is, for example, 1000 Hz.

  Here, the memory 40 will be described in order to explain the operation of the determination unit 33. The phase difference and sound pressure difference between the sounds emitted from the point sound source and input to the pair of microphones 10R and 10L vary depending on the angle indicating the direction of the point sound source and the frequency of the sound from the point sound source.

Specifically, when sound from a point sound source (not shown) is input to the pair of microphones 10R and 10L on the lower frequency side than the specific frequency, an angle indicating the direction of the point sound source and the calculation unit 32 output the sound. The relationship with the phase difference is as shown in FIG. Therefore, the upper limit value and the lower limit value of the phase difference output from the calculation unit 32 are stored in advance in the memory 40 for each center frequency of the predetermined frequency band. Table 1 shows this relationship. The angle indicating the direction of the point sound source in the present embodiment refers to a straight line connecting the midpoint of the pair of microphones 10R and 10L and the point sound source, and a vertical bisector of a straight line connecting the pair of microphones 10R and 10L. Means the angle formed by. In the present embodiment, the upper limit value and the lower limit value of the phase difference are stored for each center frequency with respect to each of the frequency bands of 125 Hz, 125 Hz, 250 Hz, 375 Hz, 500 Hz, 625 Hz, and 750 Hz. For example, referring to a table having a center frequency of 750 Hz in the memory 40 of the present embodiment, the upper limit value is 3.1 radians and the lower limit value is −3.1 radians.

Further, when the sound from the point sound source is input to the pair of microphones 10R and 10L on the higher frequency side than the specific frequency, there is a relationship between the angle indicating the direction of the point sound source and the sound pressure difference output from the calculation unit 32. As shown in FIG. Therefore, the memory 40 stores in advance an upper limit value and a lower limit value of the sound pressure difference output from the calculation unit 32 for each center frequency of the predetermined frequency band. Table 2 shows this relationship. In the present embodiment, the upper limit value and the lower limit value of the sound pressure difference are stored for each of the frequencies having a bandwidth of about 500 Hz and center frequencies of 1250 Hz, 1750 Hz, 2250 Hz, 2750 Hz, 3250 Hz, and 3750 Hz. For example, referring to a frequency band table with a center frequency of 2250 Hz in the memory 40 of the present embodiment, the upper limit value is 18 dB and the lower limit value is −19 dB.

  The determination unit 33 is a calculation unit among the upper limit value and lower limit value of the phase difference for each frequency obtained by the calculation unit 32 and the phase difference for each frequency stored in the memory 40 on the lower frequency side than the specific frequency. The ratio with the one closer to the phase difference obtained in 32 is calculated. A frequency at which this ratio is greater than a predetermined value is counted as a frequency that is wind noise. Further, the determination unit 33 obtains the calculation unit 32 among the sound pressure difference for each frequency obtained by the calculation unit 32 and the sound pressure difference upper limit value and lower limit value stored in the memory 40 on the higher frequency side than the specific frequency. Calculate the ratio with the one closer to the sound pressure difference. A frequency at which this ratio is greater than a predetermined value is counted as a frequency that is wind noise. When wind noise enters the microphones 10R and 10L, the phase difference and sound pressure difference of the sound component signal in the frequency band of the sound are the absolute values of the upper and lower limits of the phase difference and sound pressure difference stored in the memory 40. Compared to it, it becomes large enough. Therefore, the frequency band of wind noise input to the microphones 10R and 10L can be extracted by the above determination. The frequency band extracted here can be considered as a frequency band in which wind noise is dominant. Specifically, the determination unit 33 extracts the frequency band as follows.

  The determination unit 33 first determines the upper limit value or lower limit value of the phase difference stored in advance in the memory 40 and the phase difference output from the calculation unit 32 for each frequency on the lower frequency side than the specific frequency. Calculate the ratio. When the phase difference output from the calculation unit 32 is positive, the ratio with the upper limit value stored in the memory 40 is calculated. When the phase difference output from the calculation unit 32 is negative, the ratio is stored in the memory 40. The ratio to the lower limit value is calculated. Then, the determination unit 33 counts the number of frequency bands in which the obtained ratio is greater than the first predetermined value on the lower frequency side than the specific frequency. The first predetermined value is 1.4, for example. For example, in the frequency band with a center frequency of 500 Hz, when the phase difference obtained by the calculation unit 32 is −5 radians, the lower limit value of the phase difference stored in the memory 40 is −2.2 radians. The ratio is about 2.3, which is larger than the first predetermined value. Therefore, in this case, the frequency band having a center frequency of 125 Hz is counted as wind noise.

  Further, the determination unit 33 is configured such that, on the higher frequency side than the specific frequency, the ratio between the upper limit value or lower limit value of the sound pressure difference stored in advance in the memory 40 and the sound pressure difference output from the calculation unit 32 for each frequency. Is calculated. When the sound pressure difference output from the calculation unit 32 is positive, the ratio with the upper limit value stored in the memory 40 is calculated. When the sound pressure difference output from the calculation unit 32 is negative, the ratio is stored in the memory 40. The ratio with the lower limit value is calculated. Then, the determination unit 33 counts the number of frequency bands in which the obtained ratio is greater than the second predetermined value on the higher frequency side than the specific frequency. When the unit is decibels, in order to obtain the ratio, the difference between the upper limit value or lower limit value of the sound pressure difference stored in the memory 40 and the sound pressure difference output from the calculation unit 32 is the ratio. This second predetermined value is, for example, 20 dB. For example, when the sound pressure difference obtained by the calculation unit 32 is 50 dB in the wavelength band having a center frequency of 2250 Hz, the upper limit value of the sound pressure difference stored in the memory 40 is 18 dB, so the difference is 32 dB. And greater than the second predetermined value. Therefore, in this case, the frequency band whose center frequency is 2250 Hz is counted.

  Next, the determination unit 33 determines whether the sum of the number of frequency bands counted on the low frequency side from the specific frequency and the number of frequency bands counted on the high frequency side from the specific frequency is greater than the third predetermined number. Judge whether or not. Since the frequency band of wind noise is wide, it can be considered that there is wind noise when the total number of counted frequency bands is larger than a predetermined number. On the other hand, when the total number of frequency bands counted is equal to or less than a predetermined number, it can be considered that wind noise is negligible. The predetermined number is, for example, five when the number of frequency bands is six on the low frequency side and six on the high frequency side as described above.

  If the total number of counted frequency bands is greater than the predetermined number, the determination unit 33 calculates the filter gain as follows.

  It is considered that wind noise is dominant in the frequency band as the ratio calculated by the determination unit 33 is larger than the predetermined value. Further, it is considered that the larger the number of frequencies counted by the determination unit 33, the wider the wind noise. Further, it is considered that the wind noise continues as the total number of counts added for a predetermined time for each frequency increases. The determination unit 33 determines the filter gain of the filter unit 34 for suppressing wind noise based on the calculated ratio, and filters the sound signal component when the number of counted frequencies is greater than a predetermined value. Can be controlled.

  When the total number of frequency bands counted is larger than a predetermined number, the filter unit 34 filters the sound component signals output from the conversion units 31R and 31L for at least the counted frequency bands. For example, the filter unit 34 reduces the gain of a sound component signal in a frequency band in which the ratio is greater than a predetermined value. For example, the gain reduction amount of the sound component signal in the frequency band extracted by the filter unit 34 is made proportional to the magnitude of the ratio.

  On the other hand, when the total number of counted frequency bands is equal to or less than a predetermined number, the filter unit 34 does not attenuate the sound component signal for all frequency bands.

  The sound component signal output from the filter unit 34 is subjected to hearing aid processing such as gain adjustment and output restriction for each band in order to match the user's hearing with the hearing aid processing unit 35. Of the sound component signals that have been subjected to hearing aid processing by the hearing aid processing unit 35, the sound component signals of each frequency band based on the sound signal of the microphone 10R are input to the inverse conversion unit 36R, synthesized with the sound signal, and output from the filter unit 34. Of the sound component signals, the sound component signals of each frequency band based on the sound signal of the microphone 10L are input to the inverse conversion unit 36L and synthesized with the sound signal. As described above, when fast Fourier transform is used in the conversion units 31R and 31L, inverse Fourier transform (IFFT) is used in the inverse conversion units 36R and 36L. Each synthesized sound signal is output from the DSP 30.

  The sound signal output from the inverse conversion unit 36R is input to the D / A converter 50R, the sound signal output from the inverse conversion unit 36L is input to the D / A converter 50L, and each sound signal is changed from a digital signal to an analog signal. It is converted and output.

  The sound signal output from the D / A converter 50R is amplified by an amplifier (not shown) and output from the earphone 60R, and the sound signal output from the D / A converter 50L is amplified by an amplifier (not shown) and then the earphone 60L. Output from. Note that one earphone 60R is disposed in a housing in which one microphone 10R is disposed, and is attached to one ear of the user. Further, the other earphone 60L is disposed in a housing where the other microphone 10L is disposed, and is attached to the other ear of the user.

  As described above, according to the sound signal processing device of the present embodiment, the phase difference and sound pressure difference of the sound input to the microphones 10R and 10L, and the upper limit value and lower limit of the phase difference and sound pressure difference stored in the memory 40. The value is compared and the presence or absence of wind noise is determined and suppressed.

  On the lower frequency side than the specific frequency, a ratio between the phase difference of the sound input to the microphones 10R and 10L and the upper limit value or the lower limit value of the phase difference stored in the memory 40 is calculated, and the frequency is higher than the specific frequency. On the side, the ratio between the sound pressure difference of the sound input to the microphones 10R and 10L and the upper limit value or the lower limit value of the sound pressure difference stored in the memory 40 is calculated. Since the sound wavelength is long on the low frequency side and the phase difference between the sounds input to the two microphones 10R and 10L is not more than ± π radians, using the phase difference on the low frequency side makes the wind noise dominant frequency. The band can be extracted stably. On the other hand, since the diffraction of sound is small on the high frequency side and it is easy to produce the sound pressure difference of the sound input to each microphone, using the sound pressure difference on the high frequency side can stably extract the frequency band dominated by wind noise. . Thus, wind noise can be stably suppressed.

  In the sound signal processing device of this embodiment, the determination unit 33 has a predetermined value that is a ratio of the phase difference or sound pressure difference output from the calculation unit 32 to the phase difference or sound pressure difference upper limit value or lower limit value of the memory 40. When the number of larger frequency bands is larger than the predetermined number, the frequency band is filtered. On the other hand, if the difference is less than a predetermined number, no filtering is applied. Therefore, it is possible to prevent unnecessary filtering in an environment with little wind noise.

  Moreover, since the hearing aid of this embodiment can suppress a wind noise stably in a sound signal processing apparatus, it can be used favorably also in an environment with a wind.

  As mentioned above, although this invention was demonstrated to the example for embodiment, this invention is not limited to these.

  For example, in the above embodiment, the phase difference is used on the lower frequency side than the specific frequency, and the sound pressure difference is used on the higher frequency side than the specific frequency, so that the upper limit value of the phase difference or the sound pressure difference stored in the memory 40 or The ratio with the lower limit was determined. However, the present invention only needs to use the phase difference on the lower frequency side than the specific frequency and the sound pressure difference on the higher frequency side than the specific frequency, and further reduce the sound pressure difference on the lower frequency side than the specific frequency. There may be a frequency band that uses or uses a phase difference further on the high frequency side than a specific frequency.

  Hereinafter, the effects of the present invention will be described more specifically with reference to simulation examples, but the present invention is not limited to the simulation examples.

  FIG. 4 is a diagram showing sound signals input to the DSP 30 in FIG. 1 in this simulation. Specifically, FIG. 4A shows a sound signal input to the conversion unit 31R, and FIG. 4B shows a sound signal input to the conversion unit 31L. This sound signal includes an audio signal emitted from a point sound source and wind noise. However, from 2.0 seconds to 3.0 seconds and from 5.0 seconds to 6.0 seconds, no wind noise is input to the conversion units 31R and 31L, and only audio signals are input.

  5 (A) and 5 (B) are diagrams showing how the wind noise is removed and only the audio signal is extracted in FIGS. 4 (A) and 4 (B) in the same manner as FIG. is there.

  6A is a diagram showing the audio signal output from the inverse conversion unit 36R in the same way as in FIG. 4, and FIG. 6B is the same method as FIG. 4 in the audio signal output from the inverse conversion unit 36L. It is a figure shown by. As apparent from FIG. 6, immediately after 0 seconds, 3.0 seconds, and 6.0 seconds when the wind noise starts to be input to the DSP 30, the signal output from the DSP 30 is affected by the wind noise. It can be seen that as time goes by, the influence of wind noise decreases and the sound signal of FIG. 5 is approached.

  From the results of this simulation, it was shown that the wind noise can be stably suppressed according to the present invention.

  As described above, according to the present invention, a sound signal processing apparatus capable of stably suppressing wind noise is provided, and can be used in the field of hearing aids, recorders, and the like using the sound signal processing apparatus.

10R, 10L ... Microphones 20R, 20L ... A / D converter 30 ... DSP
31R, 31L ... Conversion unit 32 ... Calculation unit 33 ... Determination unit 34 ... Filter unit 35 ... Hearing aid processing unit 36R, 36L ... Inverse conversion unit 40 ... Memory 50R, 50L ... D / A converters 60R, 60L ... Earphone

Claims (3)

A conversion unit that converts each sound signal output from the pair of microphones into a sound component signal decomposed for each predetermined frequency band; and
A phase difference between the sound component signal based on the sound signal from one of the microphones and the sound component signal based on the sound signal from the other microphone for the sound component signal on a lower frequency side than a specific frequency. The sound component signal is calculated for each predetermined frequency band, and the sound component signal based on the sound signal from one of the microphones and the sound signal from the other microphone of the sound component signal on the higher frequency side than the specific frequency A calculation unit for calculating a sound pressure difference with the sound component signal based on the predetermined frequency band;
When the sound from the point sound source is input to the pair of microphones in advance, the upper limit value and the lower limit value of the phase difference based on the sound from the point sound source are the predetermined frequency on the lower frequency side than the specific frequency. A memory that is stored for each band, and an upper limit value and a lower limit value of the sound pressure difference based on the sound from the point sound source are stored for each of the predetermined frequency bands on the higher frequency side than the specific frequency;
On the lower frequency side than the specific frequency, the phase difference obtained by the calculation unit among the phase difference obtained by the calculation unit and the upper limit value and the lower limit value of the phase difference stored in the memory. The frequency band whose ratio with the closer one is larger than the first predetermined value is counted, and on the higher frequency side than the specific frequency, the sound pressure difference obtained by the calculation unit and the sound pressure difference stored in the memory A determination unit that counts a frequency band having a ratio of the upper limit value and the lower limit value closer to the one close to the sound pressure difference determined by the calculation unit than a second predetermined value;
A filter unit that performs a filtering process on at least the sound component signal in the frequency band counted by the determination unit when the number of frequency bands counted by the determination unit is larger than a third predetermined value. A characteristic sound signal processing apparatus. The sound signal processing according to claim 1, wherein the filter unit reduces a gain of the filter unit based on the ratio with respect to the sound component signal in the frequency band counted by the determination unit. apparatus. The sound signal processing device according to claim 1 or 2,
A hearing aid, wherein the pair of microphones are attached to left and right ears.

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