JP2017028526A - Out-of-head localization processing device, out-of-head localization processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an out-of-head localization processing device capable of implementing out-of-head localization with a sound quality that is preferable for a user, an out-of-head localization processing method and a program.SOLUTION: An out-of-head localization processing device 100 is configured to implement out-of-head localization using an inverse filter of external auditory meatus transfer characteristics and comprises: an input part 31 which receives input for setting a non-correction band on a frequency axis; a correction filter generation part 33 which generates a correction filter by changing a filter coefficient of the inverse filter in the non-correction band; convolution operation parts 11, 12, 21 and 22 each for performing convolution processing on a reproduction signal using spatial sound transfer characteristics; filtering parts 41 and 42 each for performing processing for using the correction filter and convoluting the correction filter in the reproduction signal processed by the convolution operation part; and a headphone 43 for outputting the reproduction signal in which the correction filter has been convoluted, towards a user U.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an out-of-head localization processing apparatus, an out-of-head localization processing method, and a program.

  Patent Document 1 describes a head related transfer function (HRTF) of the listener as a method for localizing a sound image outside the head. In the method described in Patent Document 1, when headphones or earphones are used, a reproduction signal has an inverse characteristic of a head-related transfer function from a virtual sound source to both ears of a listener and an ear canal transfer function ECTF (Ear Canal Transfer function). Folded. By doing so, it is possible to cancel the characteristics of the headphones or earphones and reproduce the sound field as if sound is heard from the direction of the virtual sound source even though sound is emitted from the vicinity of the ear. The ear canal transfer function ECTF is measured by inserting a measurement microphone into the listener's ear canal or substituting a dummy head.

JP 2002-209300 A JP2015-126268A

“Horizontal sound image localization by bandpass noise” Daisuke Morikawa, Tatsuya Hirahara IEICE Transactions A Vol. J95-A No. 4 pp 337-342

  The ear canal transfer function ECTF is a transfer function that determines sound peculiar to headphones or earphones. The ear canal transfer function ECTF includes a frequency amplitude characteristic related to sound quality and a phase characteristic related to what phase the eardrum is vibrated. However, since the out-of-head localization processing convolves the inverse characteristics of the ear canal transfer function ECTF, there may be cases where the sound quality and force peculiar to headphones or earphones cannot be obtained. Therefore, it may not be possible to perform out-of-head localization with a sound quality preferable for the user.

  In particular, the comparison of ON / OFF of the out-of-head localization processing increases the change in sound quality. That is, when the processing sound of the out-of-head localization processing is compared with the sound of the headphones themselves, the sound quality is greatly changed. Therefore, an out-of-head localization process is desired while leaving the sound quality of the headphones.

  Non-Patent Document 1 describes that 2 kHz to 12 kHz is necessary for localization of narrowband noise in order to obtain localization accuracy comparable to that of white noise. However, even if this narrow band is subjected to out-of-head localization processing for a wide-band sound source such as stereo music, the localization position may change, the sound image may be blurred, and the entire sound field may be lost. .

  The present invention has been made in view of the above points, and provides an out-of-head localization processing apparatus, an out-of-head localization processing method, and a program capable of performing out-of-head localization with a sound quality preferable for a user even when headphones or earphones are used. The purpose is to do.

  An out-of-head localization processing apparatus according to an aspect of the present invention is an out-of-head localization processing apparatus that performs out-of-head localization processing using an inverse filter of the ear canal transfer characteristic, and for setting an uncorrected band on the frequency axis. An input unit that receives an input, a correction filter generation unit that generates a correction filter by changing a filter coefficient of the inverse filter in the non-correction band, and a convolution of the reproduced signal using spatial acoustic transfer characteristics A convolution operation unit that performs processing, a filter unit that performs convolution processing on the reproduction signal processed by the convolution operation unit using the correction filter, and headphones or earphones, and convolution processing by the filter unit And an output unit that outputs the reproduced signal to the user.

  An out-of-head localization processing method according to one aspect of the present invention is an out-of-head localization processing method that performs out-of-head localization using an inverse filter of the ear canal transfer characteristic, and sets an uncorrected band based on an input from a user A step of generating a correction filter by changing a filter coefficient of the non-correction band in the inverse filter, a step of performing a convolution process on the reproduction signal using a spatial acoustic transfer characteristic, A step of convolving the correction filter with respect to the reproduction signal subjected to the convolution processing, and a step of outputting the reproduction signal convolved with the correction filter from a headphone or an earphone to a user. It is.

  A program according to an aspect of the present invention is a program for causing a computer to execute an out-of-head localization processing method for performing out-of-head localization processing using an inverse filter of the ear canal transmission characteristic, wherein the out-of-head localization processing method includes: Based on an input from a user, using a spatial acoustic transfer characteristic, a step of setting a non-correction band, a step of generating a correction filter by changing a filter coefficient of the non-correction band in the inverse filter, A step of performing a convolution process on the reproduction signal, a step of convolving the correction filter with respect to the reproduction signal subjected to the convolution process, and a reproduction signal in which the correction filter is convoluted from a headphone or an earphone. And outputting to the user.

  According to the present invention, it is possible to provide an out-of-head localization processing apparatus, an out-of-head localization processing method, and a program capable of performing out-of-head localization with sound quality preferable for a user even when headphones or earphones are used.

It is a block diagram which shows the out-of-head localization processing apparatus which concerns on this Embodiment. It is a figure which shows the structure for measuring a spatial acoustic transfer characteristic. It is a figure which shows the time characteristic of an ear canal transmission characteristic and its reverse characteristic. It is a figure which shows the frequency amplitude characteristic and reverse characteristic of an ear canal transmission characteristic. It is a figure which shows an example of the screen for setting the non-correction zone | band of a correction filter. It is a figure which shows the frequency amplitude characteristic of a correction filter. It is a figure which shows an example of the screen for setting the non-correction zone | band of a correction filter. It is a figure which shows the frequency amplitude characteristic of a correction filter. It is a figure which shows an example of the screen for setting the non-correction zone | band of a correction filter. It is a figure which shows the frequency amplitude characteristic of a correction filter. It is a figure which shows an example of the screen for setting the non-correction zone | band of a correction filter. It is a figure which shows the frequency amplitude characteristic of a correction filter.

An outline of the out-of-head localization process according to the present embodiment will be described.
The out-of-head localization processing according to the present embodiment performs out-of-head localization processing using an individual's spatial acoustic transfer characteristic (also referred to as a spatial acoustic transfer function) or an external auditory canal transfer characteristic (also referred to as an external auditory canal transfer function). In the present embodiment, the out-of-head localization processing is realized by using the spatial acoustic transmission characteristic from the speaker to the listener's ear and the external auditory canal transmission characteristic with the headphones attached.

  In the present embodiment, the ear canal transmission characteristic, which is the characteristic from the headphone speaker unit to the ear canal entrance when the headphone is worn, is used. Then, the ear canal transfer characteristic is corrected by performing a filter process using an inverse filter that shows the reverse characteristic of the ear canal transfer characteristic (also referred to as an ear canal correction function). Thereby, the external auditory canal transmission characteristic can be canceled.

  Furthermore, an uncorrected band in which the ear canal transfer characteristic correction is not performed is set according to the input from the user. That is, some bands are set as non-correction bands in all frequency bands reproducible with headphones. Specifically, in the inverse filter of the ear canal transfer characteristic, the filter coefficient of the non-correction band set by the input from the user is changed. In the non-correction band, the filter coefficient of the inverse filter is set to 0 dB so that the ear canal transfer characteristic correction by the inverse filter is not performed. In this way, it is possible to set how much the sound quality of the headphones is reflected. Therefore, it is possible to perform out-of-head localization with a sound quality preferable for a headphone user.

  For example, the user performs input for setting the non-correction band. Then, the out-of-head localization processing apparatus of the present embodiment sets so that the filter coefficient in the non-correction band becomes 0 dB among the filter coefficients of the inverse filter set in advance. Next, the out-of-head localization processing apparatus according to the present embodiment uses the inverse filter in which the filter coefficient of the non-correction band is changed as a correction filter, and convolves the correction filter with the reproduction signal. Then, the out-of-head localization processing apparatus of the present embodiment outputs a reproduction signal in which the correction filter is convoluted from headphones or earphones. In this way, it is possible to perform out-of-head localization processing while leaving the sound quality peculiar to headphones.

  Further, the non-correction band in which the filter coefficient is 0 dB can be made variable. For example, the user may be able to adjust the width and position (frequency) of the non-correction band. By doing in this way, it can adjust so that a user may become favorite sound quality.

  The out-of-head localization processing apparatus according to the present embodiment is an information processing apparatus such as a personal computer, processing means such as a processor, storage means such as a memory or a hard disk, display means such as a liquid crystal monitor, touch panel, button, keyboard, Input means such as a mouse and output means having headphones or earphones are provided. Alternatively, the out-of-head localization processing device may be a smart phone or a tablet PC.

  An out-of-head localization processing apparatus 100 according to the present embodiment is shown in FIG. FIG. 1 is a block diagram of an out-of-head localization processing apparatus. The out-of-head localization processing apparatus 100 reproduces a sound field for the user U wearing the headphones 43. Therefore, the out-of-head localization processing apparatus 100 performs out-of-head localization processing on the stereo input signals XL and XR of the left channel (hereinafter referred to as Lch) and the right channel (hereinafter referred to as Rch). The Lch and Rch stereo input signals XL and XR are music reproduction signals output from a CD (Compact Disc) player or the like. The out-of-head localization processing apparatus 100 is not limited to a physically single apparatus, and some processes may be performed by different apparatuses. For example, a part of the processing may be performed by a personal computer or the like, and the remaining processing may be performed by a DSP (Digital Signal Processor) built in the headphones 43 or the like.

  The out-of-head localization processing apparatus 100 includes an out-of-head localization processing unit 10, an input unit 31, an inverse filter storage unit 32, a correction filter generation unit 33, a display unit 34, a filter unit 41, a filter unit 42, and headphones 43. Yes.

  The out-of-head localization processing unit 10 includes convolution operation units 11, 12, 21, and 22. The convolution operation units 11, 12, 21, and 22 perform convolution processing using spatial acoustic transfer characteristics. Stereo input signals XL and XR from a CD player or the like are input to the out-of-head localization processing unit 10. Spatial acoustic transfer characteristics are set in the out-of-head localization processing unit 10. The out-of-head localization processing unit 10 convolves the spatial acoustic transfer characteristics with the stereo input signals XL and XR of each channel. The spatial acoustic transfer characteristic may be a head related transfer function HRTF.

  The spatial acoustic transfer characteristic has four transfer characteristics Ls, Lo, Ro, and Rs. The four transfer characteristics can be obtained using a measuring apparatus as shown in FIG. In FIG. 2, a left speaker 5L and a right speaker 5R are installed in front of the listener 1. In addition, a microphone 2L for sound collection is installed at the ear canal entrance of the left ear 3L of the listener 1 or at the eardrum position. A microphone 2R for sound collection is installed at the entrance of the ear canal of the right ear 3R of the listener 1 or at the eardrum position. The listener 1 may be a person or a dummy head. Therefore, in this embodiment, the listener 1 is a concept including not only a person but also a dummy head.

  The impulse response from the left speaker (SpL) 5L is measured by the left microphone 2L and the right microphone 2R. Thereby, a transfer characteristic (also referred to as a transfer function) Ls between the left speaker 5L and the left microphone 2L and a transfer characteristic Lo between the left speaker 5L and the right microphone 2R can be obtained. Further, the impulse response from the right speaker (SpR) 5R is measured by the left microphone 2L and the right microphone 2R. Thereby, the transfer characteristic Ro between the right speaker 5R and the left microphone 2L and the transfer function Rs between the right speaker 5R and the right microphone 2R can be obtained. In this way, by performing impulse response measurement twice for a certain listener 1, four transfer characteristics Ls, Lo, Ro, and Rs are obtained. Alternatively, the spatial acoustic transfer characteristic may be set by the user U selecting an appropriate one of the preset spatial acoustic transfer characteristics. Therefore, the listener 1 in FIG. 2 and the user U in FIG. 1 may be the same person or different persons. Naturally, the effect of the out-of-head localization processing is higher when the listener 1 and the user U are the same than when the listener 1 is different from the user U.

  The convolution operation unit 11 convolves the transfer characteristic Ls with the Lch stereo input signal XL. The convolution operation unit 11 outputs the convolution operation data to the adder 24. The convolution operation unit 21 convolves the transfer characteristic Ro with the Rch stereo input signal XR. The convolution operation unit 21 outputs the convolution operation data to the adder 24. The adder 24 adds the two convolution calculation data and outputs the result to the filter unit 41.

  The convolution operation unit 12 convolves the transfer characteristic Lo with the Lch stereo input signal XL. The convolution operation unit 12 outputs the convolution operation data to the adder 25. The convolution unit 22 convolves the transfer characteristic Rs with the Rch stereo input signal XR. The convolution operation unit 22 outputs the convolution operation data to the adder 25. The adder 25 adds the two convolution calculation data and outputs the result to the filter unit 42.

  In the filter units 41 and 42, inverse filters corresponding to the ear canal transmission characteristics are set. Then, an inverse filter is convoluted with the reproduction signal that has been processed by the out-of-head localization processing unit 10. The filter unit 41 convolves an inverse filter with the Lch signal from the adder 24. Similarly, the filter unit 42 convolves an inverse filter with the Rch signal from the adder 25. When the headphones 43 are worn, the inverse filter cancels the transfer characteristic between the user's ear canal entrance and the speaker. By doing so, the characteristics of the headphones 43 are corrected (cancelled). When the dummy head is used, the microphones 2R and 2L can be installed at the eardrum position, and the inverse filter in this case cancels the transfer characteristic between the eardrum and the headphone speaker unit.

  The filter unit 41 outputs the corrected Lch signal to the left unit 43L of the headphones 43. The filter unit 42 outputs the corrected Rch signal to the right unit 43R of the headphones 43. User U is wearing headphones 43. The headphone 43 outputs the Lch signal and the Rch signal toward the user U. Thereby, the sound image of the sound received by the user U is localized outside the user U's head.

  The display unit 34 includes a display device such as a liquid crystal monitor. As will be described later, the display unit 34 displays an uncorrected band setting screen and the like.

  The input unit 31 includes input devices such as a touch panel, buttons, a keyboard, and a mouse, and accepts input from the user U. Specifically, the input unit 31 receives an input for setting an uncorrected band on the frequency axis. The input unit 31 may be a switch or the like mounted on the headphones 43. The user U operates the input unit 31 to set a non-correction band on the frequency axis for correcting the filter coefficient. The set non-correction band is output to the correction filter generation unit 33. For example, the upper limit value and lower limit value of the non-correction band are output to the correction filter generation unit 33. Note that there may be two or more non-correction bands in the entire frequency band.

  The inverse filter storage unit 32 stores an inverse filter (inverse characteristic) of the ear canal transfer characteristic used for the convolution processing in the filter units 41 and 42. Note that the ear canal transfer characteristic may be a pre-measured one or may be selected from several preset characteristics. For example, a dummy head or an impulse response measurement for the user U is used for the measurement of the ear canal transfer characteristics. A microphone is attached to the dummy head or the user U, and the impulse response is measured. FIG. 3 shows an example of the ear canal transfer characteristic and its inverse characteristic obtained by impulse response measurement.

  The ear canal impulse response obtained by the measurement is subjected to discrete Fourier transform to convert from the time domain to the frequency domain. Thereby, an amplitude characteristic (amplitude spectrum, power spectrum) and a phase characteristic (phase spectrum) of each frequency are calculated. The inverse characteristic of the amplitude characteristic is an inverse filter of the ear canal transmission characteristic.

At this time, it is desirable to perform the smoothing process described in Patent Document 2 in order to suppress the listener's uncomfortable feeling in the high frequency band. Specifically, on the higher frequency side than the high frequency boundary frequency (14 kHz or higher in the present embodiment), the amplitude component of the inverse filter is set to a constant value (in the present embodiment, regardless of the amplitude characteristics of the ear canal transfer function). Is 0 dB). Here, the high-frequency boundary frequency indicates a high-frequency boundary frequency among the frequency bands in which the out-of-head sound image localization processing is performed. By this smoothing process, it is possible to prevent the occurrence of treble noise due to the notch of the frequency amplitude characteristic.
The smoothed frequency band is not included in the non-correction band of the present invention.

  FIG. 4 is a diagram showing frequency amplitude characteristics of the ear canal transfer characteristic and the smoothed inverse characteristic, and shows the inverse characteristic of the ear canal transfer characteristic in the frequency domain obtained by discrete Fourier transform of the ear canal impulse response shown in FIG. In FIG. 4, the horizontal axis represents the logarithmic scale frequency (Hz), and the vertical axis represents the amplitude (dB). The amplitude at each frequency in the frequency region of the ear canal transfer characteristic is the filter coefficient. When the inverse characteristic on the frequency axis shown in FIG. 4 is subjected to inverse discrete Fourier transform, the inverse response shown in FIG. 3 is obtained.

  The correction filter generation unit 33 reads the filter coefficient of the inverse filter stored in the inverse filter storage unit 32 and generates a correction filter. The correction filter generation unit 33 generates a correction filter by changing the filter coefficient of the inverse filter of the ear canal transfer characteristic obtained in advance. For example, the correction filter generation unit 33 changes the filter coefficient of the inverse filter in the non-correction band to 0 dB. In this way, the correction filter generation unit 33 generates a correction filter. Further, the correction filter generation unit 33 may convert the correction filter into a time domain filter by performing an inverse discrete Fourier transform on the inverse filter in which the filter coefficient is changed.

  In the setting of the non-correction band, the user can input a ratio of leaving the sound quality of the headphones. For example, when the user inputs a percentage of 0 to 100%, an uncorrected band is set according to the percentage. Specifically, the user U inputs a numerical value of the ratio of the uncorrected band that does not correct the ear canal transfer characteristic with respect to the entire frequency band. This ratio is preferably a logarithmic scale.

It is assumed that the entire frequency band is 10 Hz to 24 kHz and the sampling frequency Fs = 48 kHz. The start frequency (lower limit value) of the non-correction band is Fstart, and the end frequency (upper limit value) of the non-correction band is Fend. In this case, the logarithmic scale ratio is obtained by the following equation (1). The lower limit of the entire frequency band is not limited to 10 Hz, and may be 0 Hz or 20 Hz, for example.
100 ・ (logFend−logFstart) / (log24000-log10) (1)

  When the initial value of the uncorrected band is 4 kHz to 8 kHz, the ratio of the uncorrected band to the entire frequency band 10 Hz to 24 kHz is about 9%. When the user increases this ratio, the user moves toward a lower start frequency (lower limit value) and a higher end frequency (upper limit value).

  If the ratio of the non-correction band is set to 100%, the external auditory canal transfer characteristic is not corrected at all, and the out-of-head localization processing with the sound quality of the headphones being 100% is executed. This is called a headphone sound quality mode. On the other hand, if the ratio of the non-correction band is set to 0%, the correction is performed in the entire frequency band, so that the sound quality of the measured speaker itself is obtained. This is called a speaker sound quality mode. On the other hand, the case where the correction filter in which a part of the filter coefficient in the non-correction band is changed as described above is referred to as an intermediate sound quality mode. Thus, the mode can be switched by inputting the ratio.

  Hereinafter, setting of the non-correction band will be described in detail with reference to FIGS. 5 to 12. FIGS. 5, 7, 9, and 11 are examples of display screens that accept operations for setting the non-correction band. FIG. 6, 8, 10, and 12 are diagrams illustrating the inverse characteristics in which the filter coefficients are changed, that is, the amplitude characteristics of the correction filter.

  First, the display unit 34 displays an initial setting screen as shown in FIG. In FIG. 5, a bar for setting the non-correction band is displayed. Specifically, a bar (hatched portion) corresponding to the non-correction band is displayed in a frame indicating the entire frequency band of 10 Hz to 24 kHz. The uncorrected band is set according to the position and width of the bar. Here, 4 kHz to 8 kHz is set as the initial value of the non-correction band A. A frequency band (10 Hz to 4 kHz) lower than the non-correction band A is set as a correction band B, and a frequency band (8 kHz to 24 kHz) higher than the non-correction band A is set as a correction band C. The non-correction band A is arranged between the correction band B and the correction band C. Specifically, the user U sets the uncorrected band A by operating the mouse or the touch panel and adjusting the position and width of the bar.

  When 4 kHz to 8 kHz is the non-correction band A, the reverse characteristic is as shown in FIG. In the non-correction band A, the amplitude of the inverse filter is 0 dB. In FIG. 6, the filter coefficient of the correction filter in the non-correction band A is indicated by a bold line. That is, in FIG. 6, the filter coefficient changed by the correction filter generation unit 33 is indicated by a thick line. In the correction bands B and C, the same coefficients as the filter coefficients in FIG.

  FIG. 7 shows an example of a setting screen when changing the non-correction band A. The display unit 34 displays the setting screen shown in FIG. In FIG. 7, the bandwidth is constant and the start frequency (lower limit value) is adjusted. In FIG. 7, a white arrow indicates a cursor on the display screen, and a black arrow indicates to the user U that the range of the uncorrected band A can be changed. In FIG. 7, the non-correction band A has moved to the low frequency side compared to FIG.

  The reverse characteristics when the uncorrected band A shown in FIG. 7 is set are as shown in FIG. In the non-correction band A, the amplitude of the inverse filter is 0 dB. In FIG. 8, the filter coefficient of the correction filter in the non-correction band A is indicated by a bold line. In the correction bands B and C, the same coefficients as the filter coefficients in FIG.

  FIG. 9 shows an example of a setting screen when changing the bandwidth of the uncorrected bandwidth A. The display unit 34 displays the setting screen shown in FIG. In FIG. 9, a black arrow indicates that the start frequency (lower limit value) and end frequency (upper limit value) of the non-correction band A can be changed. As shown in FIG. 9, the non-correction band A can be widened from the initial setting (4 kHz to 8 kHz). In FIG. 9, the start frequency (lower limit value) of the uncorrected band A is 2 kHz, and the end frequency (upper limit value) is 8 kHz.

  The reverse characteristics when the uncorrected band A shown in FIG. 9 is set are as shown in FIG. In the non-correction band A, the amplitude of the inverse filter is 0 dB. In FIG. 10, the filter coefficient of the correction filter in the non-correction band A is indicated by a bold line. In the correction bands B and C, the same coefficients as the filter coefficients in FIG. In FIG. 9, the non-correction band A is expanded from the initial setting, but may be narrowed. Specifically, the start frequency and the end frequency are expanded or reduced at an equal ratio (logarithmic scale) by moving both ends of the bar to the left or right, or turning the mouse wheel.

  Furthermore, it is possible to set two non-correction bands as shown in FIGS. In FIG. 11, the non-correction band D is set on the lower frequency side than the non-correction band A of FIG. The uncorrected band D is set from 10 Hz to 200 Hz, which is the overall lower limit value. The user U can adjust the upper limit value of the non-correction band D by operating the mouse or the touch panel. The correction band B is arranged between the non-correction band A and the non-correction band D.

  The reverse characteristics when the uncorrected bands A and D shown in FIG. 11 are set are as shown in FIG. In the uncorrected bands A and D, the amplitude of the inverse filter is 0 dB. In FIG. 12, the filter coefficients of the correction filters in the non-correction bands A and D are indicated by bold lines. In the correction bands B and C, the same coefficients as the filter coefficients in FIG. The lower limit value of the non-correction band D is the entire lower limit value 10 Hz. Therefore, the user U can freely set the end frequency (upper limit value) of the non-correction band D. In this way, two uncorrected bands A and D may be set. Of course, two or more uncorrected bands may be set.

  As described above, the correction filter generation unit 33 changes the filter coefficient in the non-correction band. Then, the correction filter generation unit 33 performs inverse discrete Fourier transform on the amplitude characteristic having the changed filter coefficient. Thus, the correction filter generation unit 33 generates a correction filter by changing the filter coefficient in the inverse filter in the non-correction band. In the filter units 41 and 42, the correction filter generated by the correction filter generation unit 33 is set as an inverse filter. The filter units 41 and 42 perform convolution processing on the Lch signal and the Rch signal using a correction filter. Then, the filter unit 41 outputs the Lch signal in which the left correction filter is convoluted to the left unit 42L of the filter unit 42. The filter unit 42 outputs the Rch signal in which the right correction filter is convoluted to the right unit 42 </ b> R of the headphones 43.

  In the present embodiment, the user U can set the uncorrected band on the frequency axis by operating the input unit 31. In the non-correction band set according to the input of the user U, the correction filter generation unit 33 sets the filter coefficient to 0 dB. That is, the correction filter generation unit 33 generates a correction filter in which the filter coefficient in the non-correction band is 0. The filter unit 41 and the filter unit 42 perform a convolution process using the correction filter generated by the correction filter generation unit 33. In this way, the sound image can be localized out of the head while the sound quality of the headphones remains. Even when headphones are used, it is possible to perform out-of-head localization with sound quality preferable for the user.

  The non-correction band A is preferably set so as to include a band of 4 kHz to 8 kHz. Furthermore, it is preferable that the low frequency side non-correction band D includes a band of 500 Hz or less. In other words, the correction band B between the non-correction band A and the non-correction band D is preferably 1 kHz to 4 kHz. This is because the band that requires out-of-head localization processing is considered to be 1 kHz to 4 kHz, which has the highest sensitivity in terms of hearing. Therefore, the start frequency (lower limit value) of the non-correction band A is preferably 4 kHz or more, and more preferably 5 kHz or more. The end frequency of the non-correction band D is 500 Hz or more and 1 kHz or less. These frequencies were obtained based on experiments by a plurality of subjects. In addition, by using these frequencies, the ear canal transfer characteristic is corrected at 1 kHz to 4 kHz, which is the most sensitive to human hearing.

  Furthermore, cymbals and triangles having constituent frequencies in a high frequency band include many overtones above about 8 kHz. Therefore, if the ear canal transfer characteristic is not corrected for 8 kHz or more, the sound image is localized around the forehead. Therefore, in order to localize the sound image out of the head, the end frequency (upper limit value) of the non-correction band A is preferably 8 kHz or less. By doing so, it is possible to appropriately localize the sound image while keeping the headphone sound quality moderately. Even when headphones are used, it is possible to reproduce a sound field that can be localized outside the head with a sound quality preferable for the user.

  Since the user U can set the non-correction band, it is possible to prevent the localization position from being changed or the sound image from being blurred, so that the entire sound field is not lost. For example, it can be corrected in a wider band than in Non-Patent Document 1. It is possible to localize a sound image of one musical instrument (for example, a pipe organ or a piano) composed of a wideband frequency component without blurring. Also, in instruments with a rich harmonic structure (for example, violin, oboe, or piano bass), the localization of unfiltered low frequency overtones and filtered high frequency overtones is connected from the head to the head. Can be prevented. Furthermore, since it is possible to prevent the localization from changing only in a specific narrow band, it is possible to reproduce a sound field that is coherent as a whole and has no sense of incongruity. Even from the standpoint of sound quality alone, it is possible to prevent the sound quality of the speaker from being limited to a specific narrow band, and thus it is possible to reproduce with a unified sound quality. Therefore, it is possible to reproduce a sound field with excellent sound quality.

  By making the non-correction band variable as described above, it is possible to adjust the balance between the headphone sound quality and the out-of-head localization according to the user's preference. The headphone sound quality mode, speaker sound quality mode, and intermediate sound quality mode may be switched. For example, the mode may be switched by the headphones 43 or a switch or button provided in the input unit 31. In addition, the display unit 34 may display the corrected filter amplitude characteristic in accordance with an operation on the input unit 31.

  In the speaker sound quality mode, the filtering process is performed without changing the filter coefficient of the inverse filter. Therefore, the filter unit 41 and the filter unit 42 perform a convolution process using an inverse filter as shown in FIG. Therefore, sound field reproduction with the highest out-of-head localization feeling can be achieved with the sound quality of the speakers used for measuring the transfer characteristics Ls, Lo, Ro, and Rs.

  On the other hand, in the headphone sound quality mode, the filter coefficient is 0 dB in the entire frequency band. In other words, the filter unit 41 and the filter unit 42 do not perform the filter process. Therefore, the Lch signal and the Rch signal that have been subjected to the convolution process in the out-of-head localization processing unit 10 are output toward the user U from the left unit 43L and the right unit 43R of the headphones 43, respectively. In the headphone sound quality mode, sound field reproduction with a sense of out-of-head localization can be performed while maintaining the sound quality peculiar to headphones.

  On the other hand, in the intermediate sound quality mode, the correction filter generation unit 33 performs the convolution process using the correction filter as described above. That is, the filter unit 41 and the filter unit 42 fold the left and right correction filters into the Lch signal and the Rch signal, respectively. Then, the Lch signal and the Rch signal in which the correction filter is convoluted are output to the user U from the left unit 43L and the right unit 43R of the headphones 43, respectively. In the intermediate sound quality mode in which the external auditory canal transfer characteristic correction is not performed in the non-correction band, as described above, the filter coefficient is 0 dB in the non-correction band, and the filter coefficient of the inverse filter is used as it is in the correction band other than the non-correction band. Since the convolution process is performed using such a correction filter, sound field reproduction with a high out-of-head localization feeling can be performed while leaving the sound quality of the headphones moderate.

  Further, on-off of the out-of-head localization processing may be switched by the out-of-head localization processing unit 10. Even if the out-of-head localization processing is turned off, if the sound is reproduced in the intermediate sound quality mode, the change in sound quality at the time of switching can be reduced.

  In the above description, the sound field is reproduced from the headphones 43, but the sound field may be reproduced by the earphones. In this case, the inverse filter storage unit 32 stores the inverse filter of the ear canal transfer characteristic of the earphone, and the filter unit 41 and the filter unit 42 use the inverse filter. The output unit that outputs the reproduction signal subjected to the out-of-head localization processing to the user may have the headphones 43 or the earphones.

  The out-of-head localization processing method according to the present embodiment is an out-of-head localization processing method that performs out-of-head localization using an inverse filter of the ear canal transfer characteristic, and sets an uncorrected band based on an input from a user. A step of generating a correction filter by changing a filter coefficient of the non-correction band in the inverse filter, a step of performing a convolution process on the reproduction signal using a spatial acoustic transfer characteristic, and a convolution A step of convolving the correction filter with respect to the processed reproduction signal; and a step of outputting the reproduction signal with the correction filter convoluted to a user from a headphone or an earphone. is there.

  Part or all of the signal processing may be executed by a computer program. The programs described above can be stored and provided to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

DESCRIPTION OF SYMBOLS 10 Out-of-head localization processing part 11 Convolution operation part 12 Convolution operation part 21 Convolution operation part 22 Convolution operation part 24 Adder 25 Adder 31 Input part 32 Inverse filter memory | storage part 33 Correction filter production | generation part 41 Filter part 42 Filter part 43 Headphone 100 Out-of-head localization processor

Claims (5)

An out-of-head localization processing device that performs out-of-head localization processing using an inverse filter of the ear canal transfer characteristic,
An input unit for receiving an input for setting a non-correction band on the frequency axis;
A correction filter generation unit that generates a correction filter by changing a filter coefficient of the inverse filter in the non-correction band;
A convolution operation unit that performs a convolution process on the reproduction signal using the spatial acoustic transfer characteristics;
A filter unit that performs a convolution process on the reproduction signal processed by the convolution operation unit using the correction filter;
An out-of-head localization processing apparatus, comprising: an output unit that has headphones or earphones and outputs a reproduction signal convolved by the filter unit to a user.   The out-of-head localization processing apparatus according to claim 1, wherein a filter coefficient of the inverse filter is changed to 0 dB in the non-correction band.   The out-of-head localization processing apparatus according to claim 1, wherein two or more non-correction bands are provided. An out-of-head localization processing method for performing out-of-head localization using an inverse filter of the ear canal transfer characteristic,
Setting an uncorrected band based on input from a user;
A step of generating a correction filter by changing a filter coefficient of the non-correction band in the inverse filter;
Performing a convolution process on the reproduced signal using the spatial acoustic transfer characteristics;
A step of convolving the correction filter with respect to the reproduced signal subjected to the convolution processing;
An out-of-head localization processing method comprising: outputting a reproduction signal in which the correction filter is convoluted from a headphone or an earphone to a user. A program for causing a computer to execute an out-of-head localization processing method for performing out-of-head localization processing using an inverse filter of the ear canal transfer characteristic,
The out-of-head localization processing method is:
Setting an uncorrected band based on input from a user;
A step of generating a correction filter by changing a filter coefficient of the non-correction band in the inverse filter;
Performing a convolution process on the reproduced signal using the spatial acoustic transfer characteristics;
A step of convolving the correction filter with respect to the reproduced signal subjected to the convolution processing;
Outputting a reproduction signal in which the correction filter is convoluted from a headphone or an earphone to a user.

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