JP2009260574A - Sound signal processing device, sound signal processing method and mobile terminal equipped with the sound signal processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to reduce a structure or computation processing quantity necessary for computation and reproduce an appropriate sound when reproducing a stereophonic sound. <P>SOLUTION: Head-related transfer functions measured by using a dummy head are thinned within a limited number of samples, and the result is stored as a head-related transfer function database in a memory section 32. A processing section 33 extracts a transfer function at an indicated position of sound source from the limited number of samples of the head-related transfer functions within the stored head-related transfer function database. The input sound signal is multiplied by the extracted transfer function, and a sound signal with two channels is obtained by a calculation section 37 to create a binaural stereophonic sound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an audio signal processing device and an audio signal processing method suitable for application to a relatively small electronic device that handles an audio signal such as a mobile phone terminal, and a mobile terminal equipped with the audio signal processing device. The present invention relates to a technique for reproducing stereophonic sound.

  Conventionally, various portable audio devices that handle audio signals have been put into practical use. For example, mobile phone terminals that download and store music data and play back the stored music data from attached headphones have become widespread. Various so-called portable playback devices that do not have a function as a mobile phone terminal and store and play back music data have been put into practical use.

  In general, a device having a function of reproducing music data or the like is connected to a headphone and played from the headphone. There is also a device in which a small speaker is built in and output from the built-in speaker.

  Normally, when music is played back on this type of device, the input audio signal is generally a 2-channel audio signal. Therefore, when reproducing from the headphones, the audio signals of the two channels are supplied as they are to the left and right channel units of the headphones and output. However, a general two-channel audio signal is a so-called stereophonic audio signal that provides correct stereophonic sound when a speaker and a listener placed at a certain interval face each other.

On the other hand, a binaural audio signal that is reproduced with correct stereophonic sound when a headphone is worn on the listener's head is known as an audio signal reproduced from the headphones.
The process of generating a 2-channel binaural audio signal is possible by using a DSP integrated in recent years, and has been put to practical use in a highly functional audio processing apparatus. For example, as a headphone device that is used in combination with a video playback device, a device that performs a process of reproducing stereophonic sound when a video program such as a movie is viewed has been put into practical use.

Japanese Patent Application Laid-Open No. 2004-228688 discloses a process for processing an audio signal collected by a 2-channel binaural method.
JP 2005-223713 A

  As described above, mobile phone terminals are widely used as one of portable sound reproducing apparatuses. If the processing circuit for generating the above-described 2-channel binaural audio signal is built in this mobile phone terminal, headphones can be connected to the mobile phone terminal to reproduce music and the like with correct stereophonic sound. This is preferable.

  However, the processing configuration for generating a conventional binaural audio signal requires a very large arithmetic processing using an integrated circuit having a very large circuit configuration called a DSP. For this reason, for example, it has been impossible to incorporate it in a portable electronic device such as a mobile phone terminal in terms of arithmetic processing capability and cost. A large amount of calculation processing is not preferable because the battery duration is shortened.

  As another problem, the conventional processing configuration for generating a binaural audio signal has a problem that occurs because it is based on data obtained by analyzing the actually collected sound. In other words, the data for analysis was obtained by using a dummy head shaped like a human head and picking up the sound from the actual sound source with a microphone attached to the pinna of the dummy head. is there. For this reason, when a listener having a head size that substantially matches the size of the dummy head listens, the appropriate stereophonic sound is reproduced, but when a listener with a different head size listens, It may not be.

  The present invention has been made in view of such a point, and an object of the present invention is to reduce the configuration and the amount of calculation processing necessary for calculation processing and perform good reproduction when performing three-dimensional sound reproduction processing. And

  In the present invention, the head-related transfer function measured using the dummy head is thinned out to a limited number of samples and stored as a head-related transfer function database. Then, the transfer function of the instructed sound source position is extracted from the limited number of sample head transfer functions in the stored head transfer function database. The extracted transfer function is convoluted with the input audio signal to obtain a 2-channel audio signal for generating binaural stereophonic sound.

  According to the present invention, by preparing a database of head related transfer functions thinned to a limited number of samples, it is possible to reduce the storage capacity of the storage means required by the device that performs audio signal processing. Further, by performing the calculation process using the head-related transfer function from which the number of samples is thinned, the calculation processing amount for generating binaural stereophonic sound can be reduced.

  According to the present invention, it is possible to reduce the storage capacity of the storage means required by the device that performs the audio signal processing, and it is possible to reduce the amount of calculation processing for generating binaural stereophonic sound. Therefore, according to the present invention, the device configuration can be simplified, and a configuration suitable for incorporation in a portable electronic device such as a mobile phone terminal can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In this embodiment, the present invention is applied to a mobile phone terminal, which is a wireless communication terminal configured to be small for portable use. In the audio signal processing function unit built in the mobile phone terminal, the processing described below is executed.

First, an overall configuration example of the mobile phone terminal according to the present embodiment will be described with reference to FIG.
As shown in FIG. 2, the control part 11 is provided and this control part 11 controls the processing operation of each part in a mobile telephone terminal. The control unit 11 exchanges data with each unit in the terminal via the control line 28.

  In addition, the mobile phone terminal according to the present embodiment includes a communication unit 12 that performs wireless communication processing necessary as a communication terminal, and an antenna 13 is connected to the communication unit 12. The communication unit 12 performs wireless communication with a base station for wireless telephone, and performs bidirectional data transmission with the base station. The communication unit 12 sends the data received from the base station side to each unit in the terminal via the data line 29. Also, the data transmitted from each unit 17 in the terminal via the data line 29 is transmitted to the base station side.

In addition to the communication unit 13, the memory 14, the display unit 15, the sound processing unit 17, and the stereophonic sound processing unit 21 are connected to the data line 29. The memory 14 stores a program necessary for operating the terminal according to the present embodiment, various data stored by the user, and the like. The memory 14 also stores audio signals such as music data obtained by downloading. This memory 14 may also be used as a storage means for a database to be described later.
As the display unit 15, a liquid crystal display, an organic EL display, or the like is used as a display unit, and various information is displayed under the control of the control unit 11. At the time of a setting operation to be described later, the user performs a setting operation on the operation unit 16 according to the display on the display unit 15.
The operation unit 16 includes dial keys such as numbers and symbols necessary for a mobile phone terminal, various function keys, and the like. The operation information of each key constituting these operation units 16 is supplied to the control unit 11.

The audio processing unit 17 is a processing unit that processes audio signals, and is connected to a speaker 18 and a microphone 19. The speaker 18 and the microphone 19 are used as a receiver during a call. That is, the audio data supplied from the communication unit 12 to the audio processing unit 17 is demodulated by the audio processing unit 17 into an analog audio signal, and is subjected to analog processing such as amplification and emitted from the speaker 18. In addition, the audio signal collected by the microphone 19 is modulated into digital audio data by the audio processing unit 17, and the modulated audio data is supplied to the communication unit 12 to perform wireless transmission or the like.
Of the audio data supplied to the audio processing unit 17, audio to be output as 3D sound is supplied to the 3D sound processing unit 21 described below for processing.

  The mobile phone terminal according to the present embodiment includes a stereophonic sound processing unit 21. The stereophonic sound processing unit 21 is a processing unit that generates a two-channel audio signal as binaural stereophonic sound. The audio signal to be processed by the stereophonic sound processing unit 21 is read from the memory 14 or the like and supplied via the data line 29 in addition to the case where the audio signal is supplied from the audio processing unit 17 or received by the communication unit 12. Any audio signal may be used, such as when audio data is supplied via the data line 29. Specific processing for generating a two-channel audio signal as binaural stereophonic sound in the stereophonic sound processing unit 21 will be described later with reference to FIG.

The audio signal generated by the stereophonic sound processing unit 21 is output from the two speakers 22L and 22R for the left and right channels built in the mobile phone terminal body, and headphones (not shown) connected to the output terminal 23. ) May be output. Since the speakers 22L and 22R are speakers built in the mobile phone terminal main body, they are speakers using a relatively small speaker unit. However, the listener 22 around the terminal main body can hear the reproduced sound. It is a speaker that amplifies to the extent possible and outputs it.
In addition, when outputting from the headphones, in addition to the case where the headphones are directly connected to the output terminal 23 and so-called wired connection, a short-range wireless communication unit that performs wireless communication with the headphones by, for example, Bluetooth (trademark) method is incorporated. Then, a configuration may be adopted in which an audio signal is supplied to the headphones via the short-range wireless communication unit.

Next, a configuration example of the stereophonic sound processing unit 21 illustrated in FIG. 2 will be described with reference to FIG.
FIG. 1 is a diagram showing an example of the overall configuration of the stereophonic sound processing unit 21 according to the present embodiment.
If it demonstrates in order along the flow of a signal from the left side of FIG. 1, it has the sound source direction setting part 31 first. The sound source direction setting unit 31 sets a position where the sound source is localized in the stereophonic sound generated by the audio signal to be output. The sound source direction is set to a predetermined position for each audio signal to be processed, for example, based on the control of the control unit 11 shown in FIG. Alternatively, if there is an instruction about the sound source position in the additional information of the audio signal to be processed, the position is set. Alternatively, the sound source position may be freely set by a user operation of the operation unit 16 shown in FIG.

  The sound source position data output from the sound source direction setting unit 31 is supplied to the HRTF processing unit 33. The HRTF processing unit 33 is a processing unit that processes a head-related transfer function (HRTF), and selects an appropriate one from the head-related transfer functions stored in the HRTF (head-related transfer function) database 32. Extract head-related transfer function. The HRTF database 32 stores the head-related transfer functions of the left and right channels at respective sound source positions of 360 ° around the horizontal direction around the listener's position. The database 32 uses, for example, the memory 14 shown in FIG. Alternatively, a dedicated storage unit may be prepared in the stereophonic sound processing unit 21. In the present embodiment, as the head-related transfer function to be stored in the HRTF database 32, the data amount is greatly increased as the sampling value obtained by thinning out the sampling value of the original head-related transfer function measured using the dummy head. As reduced data. The sound source positions indicated in the database are also relatively coarse position intervals, for example, as data of sound source positions around 360 ° in 10 ° increments.

  The head-related transfer function extracted by the HRTF processing unit 33 is supplied to the personalization unit 34. The personalization unit 34 corrects the head related transfer function supplied from the HRTF processing unit 33 using the data of the model of the head related transfer function calculated by the HRTF model calculating unit 36. The head transfer function model data calculated by the HRTF model calculation unit 36 is calculated based on the listener head size data set by the size setting unit 35. Therefore, the personalization unit 34 performs correction based on the size of the listener's head set by the size setting unit 35. The setting of the listener's head size in the size setting unit 35 is performed by, for example, displaying the stereoscopic sound setting screen on the display unit 15 by the operation of the operation unit 16 shown in FIG. This is executed by selecting the size of the mouse and the size of the pinna by user operation. The set values of the listener's head and auricle size are stored in the memory 14 and read out.

  The head-related transfer function corrected by the personalization unit 34 is supplied to the stereophonic sound calculation unit 37. The stereophonic sound calculation unit 37 obtains a 2-channel audio signal as a binaural signal that has been made stereophonic by performing arithmetic processing using the supplied head-related transfer function for the audio signal input to the audio signal input unit 38.

  The two-channel audio signal obtained by the stereophonic sound calculation unit 37 is supplied to the headphones 24 connected to the output terminal 23 for output. Alternatively, the two-channel audio signal obtained by the stereophonic sound calculation unit 37 is supplied to the crosstalk cancellation unit 39 to remove the crosstalk component of the two channels, and then the speaker built in the mobile phone terminal body Output from 22L and 22R. As already described, the transmission from the mobile phone terminal body to the headphones 24 may be performed wirelessly.

Next, specific examples of each part in the stereophonic sound processing unit 21 will be described with reference to FIG.
FIG. 3 shows a configuration example of generation processing of a head related transfer function (HRTF) stored in the HRTF database 32. Since the processing configuration shown in FIG. 3 is processing for generating data to be stored in the database, it is prepared when the manufacturer of the mobile phone terminal manufactures software to be stored in the terminal. .

As shown in FIG. 3, the HRTF database 51 storing the measured head-related transfer functions is prepared first. The head-related transfer function stored in the database 51 is a microphone that is mounted on both ears of the dummy head, performs measurement to collect the impulse response of the sound emitted at each sound source position, and obtains the measured value. Based on the head-related transfer function. The dummy head used for this measurement is of a standard size. The sound picked up from each sound source position is a signal obtained by measuring an impulse response at 512 sample points with a predetermined sampling period in a sound collection processing configuration (not shown). The head-related transfer function composed of the 512 sample point signals is stored as a head-related transfer function at one sound source position. The sound source position is set to a position in increments of 5 °, for example, at 360 ° in the horizontal direction around the dummy head. The head-related transfer function of each sound source position includes binaural time difference information (ITD: Inter-aural Time Differences) and amplitude information (MPS: Minimum Phase Systems).
The head-related transfer functions stored in the database 51 are known as general head-related transfer functions. If an existing head-related transfer function can be used, it may be used as it is.

  Then, the binaural time difference extracting unit 52 extracts the binaural time difference information ITD from the head-related transfer functions stored in the database 51 for each sound source position data. In addition, the amplitude information MPS in the head-related transfer function stored in the database 51 is extracted by the minimum phase system converter 53 and converted into a necessary data format. The converted amplitude information MPS is supplied to the sample number conversion unit 54 to perform processing for reducing the number of samples. Here, a process of thinning 512-sample signals into 32 samples is performed. The number of samples other than 32 samples may be thinned out.

The binaural time difference information ITD extracted by the binaural time difference extraction unit 52 and the amplitude information MPS obtained by converting the number of samples by the sample number conversion unit 54 are supplied to the spatial resampling unit 55 for each sound source position. It is assumed that the head-related transfer function is composed of 32-sample impulse response values. At this time, the spatial resampling unit 55 thins out the sound source position data in units of 5 ° as data of the sound source position in units of 10 °.
The head-related transfer function obtained by the spatial re-sampling unit 55 in this manner by using 32 samples of signals at each 10 ° source position is processed HRTF database 32 in the mobile phone terminal shown in FIG. Remember me.

Next, a processing configuration example in the HRTF processing unit 33 shown in FIG. 1 will be described with reference to FIG.
As shown in FIG. 4, the sound source instruction data from the sound source direction setting unit 31 is supplied to the candidate extraction unit 61 in the HRTF processing unit 33. The candidate extraction unit 61 extracts a plurality of head related transfer functions at a sound source position close to the instructed sound source position from the head related transfer functions stored in the HRTF database 32. For example, when the sound source position is instructed to be 13 ° from the front to the right, the 10 ° head-related transfer function and the 20 ° head-related transfer function stored in the processed HRTF database 32 are extracted.
The binaural time difference information in the extracted head-related transfer function is supplied to the ITD processing unit 62, and the amplitude information is supplied to the MPS processing unit 63.

  Then, each information is supplied to the interpolation processing unit 64. The interpolation processing unit 64 uses a plurality of head-related transfer functions supplied from the ITD processing unit 62 and the MPS processing unit 63 to interpolate the head-related transfer function at the sound source position designated by the sound source direction setting unit 31. Generate by insertion. For example, when the sound source position is 13 ° from the front to the right side, a process of multiplying a head transfer function of 10 ° and a head transfer function of 20 ° by a ratio corresponding to each position is performed. Generate a head-related transfer function of position. When the instructed sound source position and the sound source position stored in the HRTF database 32 substantially match, interpolation is not performed. In addition, it is good also as a structure which approximates the instruct | indicated sound source position to the sound source position stored in the processed HRTF database 32 as a structure which does not perform the interpolation in the interpolation process part 64. FIG.

FIG. 5 is a diagram showing a processing configuration example in the personalization unit 34 shown in FIG.
The processing in the personalization unit 34 is executed based on the listener head and pinna size data already set by the size setting unit 35 shown in FIG.
Here, an example of the size setting processing state will be described. For example, the operation unit 16 of the mobile phone terminal is operated to set the head size setting mode, and a screen for setting the size is displayed on the display unit 15.
FIG. 8 shows an example of a setting screen in that case. In this example, the size of the head can be selected by user operation from three types of “large”, “standard”, and “small”. In addition, as an example, the size of the auricle can be selected by a user operation from three types of “large”, “standard”, and “small”. In the example of FIG. 8, the head size is selected as “standard”, and the pinna size is selected as “small”.
Note that the selection may be made more finely than the example shown in FIG. For example, each size may be selected not in three stages but in four or more stages. Further, as the size of the head, the size of the head in the horizontal direction and the size of the head in the vertical direction may be individually selectable. Alternatively, the approximate shape of the head may be selected from a round shape, an elongated shape, and the like, and then a size such as “large”, “standard”, and “small” may be selected.

The personalization unit 34 that performs the correction process according to the size, the binaural time difference information ITD as a head-related transfer function interpolated (or not interpolated) from the interpolation processing unit 64 shown in FIG. And amplitude information MPS are supplied. In addition, the listener's head and auricle size data already set by the size setting unit 35 shown in FIG. 1 is also supplied.
In addition, HRTF model measurement data 36a is prepared, and data of changes in each size of the head-related transfer function is stored. Of the change data at each size of the head related transfer function stored in the HRTF model measurement data 36a, data corresponding to the size set at that time is extracted by the extraction unit 36b.

  Then, the personalization unit 34 corrects the binaural time difference information ITD and the amplitude information MPS supplied from the interpolation processing unit 64 according to the currently set size using the data extracted by the extraction unit 36b. The binaural time difference information ITD ′ and the amplitude information MPS ′ are used. Details of the size correction processing will not be described here, but the head-related transfer function in the frequency band of the middle to low frequency range is mainly affected by the size of the head size. In addition, the size of the pinna mainly affects the head-related transfer function in the high frequency range.

  The binaural time difference information ITD ′ and amplitude information MPS ′, which are head-related transfer functions corrected by the personalization unit 34, are supplied to the stereophonic sound calculation unit 37 shown in FIG. 1 and input to the audio input unit 38. On the other hand, the head-related transfer function is convoluted to obtain a two-channel audio signal that reproduces the stereophonic sound by the binaural method.

FIG. 6 is a diagram illustrating a configuration example of the stereophonic sound calculation unit 37.
The binaural time difference information ITD ′ corrected by the personalization unit 34 is supplied to the phase information processing unit 71, and the left and right indicated by the binaural time difference information ITD ′ is supplied to the audio signal input from the audio input unit 38. It is assumed that the two-channel audio signal is added with the time difference. Then, the left and right channel audio signals L and R obtained by the phase information processing unit 71 are supplied to the FIR filters 72L and 72R of the respective channels. Each of the FIR filters 72L and 72R adjusts the amplitude based on the supplied amplitude information MPS ′ to obtain an audio signal that reproduces stereophonic sound by a binaural method.

FIG. 7 is a configuration example of an output unit that outputs the binaural audio signal generated in this way for two channels.
In this example, two-channel audio signals L and R are supplied to the output terminal 23 via the changeover switches 81L and 81R, respectively, and sound is emitted from the left and right driver units of the headphones 24 connected to the output terminal 23. In this way, the listener wearing the headphones 24 can hear the position of the sound source as sound in the direction set by the sound source direction setting unit 31 (FIG. 1).

  In addition, the two-channel audio signals L and R are supplied to the crosstalk cancellation unit 39 via the changeover switches 81L and 81R, respectively. The crosstalk cancel unit 39 includes coefficient multipliers 82L and 82R, adders 83L and 83R, and amplifiers 84L and 84R. The crosstalk cancel unit 39 cancels the crosstalk component of the two-channel signal and performs normal two-channel audio. Signal. The audio signals of the left and right channels whose crosstalk components are canceled by the crosstalk canceling unit 39 are output from the speakers 22L and 22R incorporated in the mobile phone terminal main body for the respective channels. The sound output from the speakers 22L and 22R can be heard by the listener facing the speakers 22L and 22R as the sound in the direction set by the sound source direction setting unit 31 (FIG. 1).

  As described above, according to the present embodiment, since the stereophonic sound calculation unit 37 that generates a binaural sound signal is built in the mobile phone terminal, the listener wearing the headphones listens to the stereophonic sound at the designated sound source position. It becomes possible to make it. In this case, in the case of the present embodiment, as the head related transfer function database 32 to be prepared, as shown in FIG. 3, data obtained by greatly reducing the number of samples and the sound source position from the original head related transfer function is obtained. Since the information is stored, the amount of information stored in the database 32 can be greatly reduced. In addition, the processing configuration for reading out the head-related transfer function from the database 32 and performing arithmetic processing is an operation that uses the head-related transfer function with a small amount of information, so the burden on the circuit in the mobile phone terminal is reduced. Therefore, it is possible to incorporate a stereophonic sound processing circuit in an electronic device such as the mobile phone terminal shown in FIG. 2 without increasing the load on the circuit or the like.

  Reducing the number of samples of the head-related transfer function leads to deterioration in the reproduction accuracy of the reproduced stereophonic sound. However, in this example, the size of the listener's head is set, correction is performed based on each setting, and the accuracy is increased from that point, which is accompanied by a decrease in the number of head transfer function samples. It functions to compensate for the deterioration in the reproduction accuracy of stereophonic sound. By setting not only the size of the head but also the size of the auricle, the conversion accuracy can be further improved.

  Further, in the case of the present embodiment, as shown in FIG. 7, as the configuration including the crosstalk cancellation unit 39, the same 3D sound as the case of reproducing from the headphones can be output from the speaker in the terminal body. Therefore, it is possible to cope with the case where the headphones are not used.

  In the embodiment described so far, an example in which a stereophonic sound processing circuit is built in a mobile phone terminal has been described. However, the above-described various electronic devices that reproduce and process audio signals (audio signals) are described above. The stereophonic sound processing unit described in the embodiment may be incorporated. For example, the stereophonic sound processing unit described in the above-described embodiment may be incorporated in a portable music player that stores and reproduces music data.

It is a block diagram which shows the audio signal processing structural example by one embodiment of this invention. It is a block diagram which shows the structural example of the mobile telephone terminal to which one embodiment of this invention is applied. It is the block diagram which showed the example of a creation process structure of the database by one embodiment of this invention. It is the block diagram which showed the example of a process structure of the head related transfer function by one embodiment of this invention. It is the block diagram which showed the correction process structural example of the head related transfer function by one embodiment of this invention. It is the block diagram which showed the processing structural example of the audio | voice signal using the head-related transfer function by one embodiment of this invention. It is the block diagram which showed the example of a structure of the output part by one embodiment of this invention. It is explanatory drawing which showed the example of a display of the setting screen by one embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Control part, 12 ... Communication part, 13 ... Antenna, 14 ... Memory, 15 ... Display part, 16 ... Operation part, 17 ... Sound processing part, 18 ... Speaker, 19 ... Microphone, 21 ... Stereophonic sound processing part, 22L , 22R ... speaker, 23 ... output terminal, 24 ... headphone, 28 ... control line, 29 ... data line, 31 ... sound source direction setting unit, 32 ... processed HRTF database, 33 ... HRTF processing unit, 34 ... personalization unit, 35 ... Size setting section, 36 ... HRTF model calculation section, 37 ... Stereophonic sound calculation section, 38 ... Audio input section, 39 ... Crosstalk cancellation section, 51 ... HRTF database, 52 ... Binaural time difference extraction section, 53 ... Minimum phase system Conversion unit, 54 ... Sample number conversion unit, 55 ... Spatial resampling unit, 61 ... Candidate extraction unit, 62 ... ITD processing unit, 63 ... MPS process Parts, 64 ... interpolation processing section, 71 ... phase information processing unit, 72L, 72R ... FIR filter, 81L, 81R ... changeover switch

Claims (7)

A head-related transfer function database that stores a head-related transfer function measured using a dummy head by thinning out a limited number of samples;
A transfer function extracting unit that extracts a transfer function of the designated sound source position from a limited number of sample head transfer functions stored in the head transfer function database;
A stereophonic sound processing unit that convolves the transfer function extracted by the transfer function extraction unit with the input audio signal to obtain a two-channel audio signal for generating binaural stereophonic sound; and
An audio signal processing apparatus comprising: an output unit configured to output a 2-channel audio signal obtained by the stereophonic sound processing unit. A correction unit that corrects the head-related transfer function extracted by the transfer function extraction unit according to a designated head size, and supplies the corrected head-related transfer function to the stereophonic sound processing unit. Item 2. The audio signal processing device according to Item 1. The audio signal processing device according to claim 2, wherein the correction unit also corrects the head-related transfer function by designating a pinna size. The audio signal processing apparatus according to claim 1, wherein the output unit is a terminal or a transmission processing unit that outputs audio signals to headphones. 2. The output unit includes a cancel processing unit that cancels crosstalk of a two-channel audio signal, and two speakers that output a two-channel audio signal from which crosstalk has been canceled by the cancel processing unit. Or the audio | voice signal processing apparatus of 2. The head-related transfer function measured using a dummy head is thinned out to a limited number of samples and stored as a head-related transfer function database.
From the head related transfer functions of the limited number of samples in the stored head related transfer function database, extract the transfer function of the indicated sound source position,
An audio signal processing method for obtaining a 2-channel audio signal for generating binaural stereophonic sound by convolving the extracted transfer function with an input audio signal. A head-related transfer function database that stores a head-related transfer function measured using a dummy head by thinning out a limited number of samples;
A transfer function extracting unit that extracts a transfer function of the designated sound source position from a limited number of sample head transfer functions stored in the head transfer function database;
A stereophonic sound processing unit that convolves the transfer function extracted by the transfer function extraction unit with the input audio signal to obtain a two-channel audio signal for generating binaural stereophonic sound; and
The portable terminal provided with the audio | voice signal processing apparatus provided with the output part which outputs the audio | voice signal of 2 channels obtained by the said stereophonic sound processing part.

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