Acoustic processing system and acoustic processing method

Abstract

To provide an acoustic processing system and an acoustic processing method which are suitable to improvement in the deviation of auditory localization.SOLUTION: In an acoustic processing system including a pre-processing unit and an acoustic processing unit, the acoustic processing unit comprises: an IACF calculation part which acquires a right / left ear mutual correlation function when the sounds output from a plurality of speakers are heard at a prescribed hearing position; a calculation part having a target position decision section which decides a target position on the basis of the right / left ear mutual correlation function within a prescribed range in the right / left ear mutual correlation functions acquired by the IACF calculation part and a delay amount calculation section which calculates a delay amount on the basis of the target position decided by the position decision section; and a processing part which has a delay processing section that delays an audio signal being a signal of the sound output from at least one of the plurality of speakers on the basis of the delay amount calculated by the delay amount calculation section. The right / left ear mutual correlation function within the prescribed range is the right / left ear mutual correlation function within a range of ±n (n is a positive value greater than 1) milliseconds.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an audio processing system and an audio processing method. [Background technology]

[0002] Generally, speakers are installed in multiple positions inside a vehicle. For example, the right front speaker in the right door and the left front speaker in the left door are installed in positions that are symmetrical across the center line of the vehicle interior. However, these speakers are not in symmetrical positions when considering the listening position of the listener (driver's seat, passenger seat, back seat, etc.).

[0003] For example, when a listener sits in the driver's seat, the distance between the right front speaker and the listener is not equal to the distance between the left front speaker and the listener. As an example, in the case of a right-hand drive vehicle, the former distance is shorter than the latter distance. Therefore, when sounds are simultaneously output from the speakers in both doors, the sound output from the right front speaker generally reaches the ears of the listener sitting in the driver's seat, and then the sound output from the left front speaker. The difference in distance between the listener's listening position and each of the multiple speakers (the difference in the time it takes for the reproduced sounds emitted from each speaker to arrive) causes a bias in the sound image localization due to the Haas effect.

[0004] Various techniques are known for improving such bias in sound image localization (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-67087 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional technology exemplified by Patent Document 1 may not be able to sufficiently improve the bias in sound image localization.

[0007] In view of the above circumstances, an object of the present invention is to provide a sound processing system and a sound processing method suitable for improving the bias in sound image localization. [Means for solving the problem]

[0008] An acoustic processing system according to an embodiment of the present invention includes a function acquisition unit that acquires an interaural cross-correlation function when sounds output from a plurality of speakers are listened to at a predetermined listening position, a position determination unit that determines a target position based on a predetermined range of the interaural cross-correlation functions acquired by the function acquisition unit, a delay amount calculation unit that calculates a delay amount based on the target position determined by the position determination unit, and a delay unit that delays an audio signal, which is a signal of the sound and is output to at least one of the plurality of speakers, based on the delay amount calculated by the delay amount calculation unit. The predetermined range of the interaural cross-correlation function is an interaural cross-correlation function in the range of ±n (where n is a positive value greater than 1) milliseconds. Effect of the Invention

[0009] According to one embodiment of the present invention, there is provided a sound processing system and a sound processing method suitable for improving bias in sound image localization. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic diagram of a vehicle in which a sound processing system according to an embodiment of the present invention is installed. [Diagram 2] 1 is a block diagram showing a hardware configuration of a sound processing device according to an embodiment of the present invention. [Diagram 3] 1 is a functional block diagram of a sound processing system according to an embodiment of the present invention. [Figure 4] FIG. 2 is a functional block diagram showing an impulse response acquisition unit according to an embodiment of the present invention. [Diagram 5] FIG. 2 is a functional block diagram showing a processing unit according to an embodiment of the present invention. [Figure 6] 5 is a flowchart showing pre-processing executed in a pre-processing unit according to an embodiment of the present invention. [Figure 7] 5 is a flowchart showing acoustic processing executed by an acoustic processing unit according to an embodiment of the present invention. [Figure 8] FIG. 4 is a functional block diagram illustrating a calculation unit according to an embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing an example of an interaural cross-correlation function calculated by an IACF calculation unit according to an embodiment of the present invention. [Figure 10] 1 is a diagram for explaining a method for determining a target position according to an embodiment of the present invention; [Figure 11] FIG. 11 is a diagram showing an example of an interaural cross-correlation function calculated by an IACF calculation unit after a time alignment process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following description relates to a sound processing system and a sound processing method according to an embodiment of the present invention.

[0012] 1 is a diagram showing a vehicle A (a right-hand drive vehicle as an example) in which a sound processing system 1 according to an embodiment of the present invention is installed. As shown in FIG. 1, the sound processing system 1 includes a sound processing device 2, a pair of left and right speakers SP FR , S.P. FL It also has a binaural microphone MIC.

[0013] Speaker SP FR is the right front speaker embedded in the right door (driver's seat side door). FL is a left front speaker embedded in the left door (passenger seat side door). Vehicle A may further be provided with another speaker (for example, a rear speaker) (i.e., three or more speakers may be provided).

[0014] The binaural microphone MIC is configured, for example, by incorporating a microphone into each ear of a dummy head that imitates a human head. In the following, the microphone incorporated into the right ear of the dummy head is referred to as the "microphone MIC." R The microphone built into the left ear of the dummy head is marked "MICROPHONE L " is written.

[0015] Fig. 2 is a block diagram showing a hardware configuration of the sound processing device 2. As shown in Fig. 2, the sound processing device 2 includes a player 10, an LSI (Large Scale Integration) 11, a D / A converter 12, an amplifier 13, a display unit 14, an operation unit 15, and a flash memory 16.

[0016] The player 10 is connected to a sound source. The player 10 reproduces an audio signal input from the sound source and outputs the signal to the LSI 11.

[0017] The sound source is, for example, a disk medium such as a CD (Compact Disc) or SACD (Super Audio CD) that stores digital audio data, or a storage medium such as a HDD (Hard Disk Drive) or USB (Universal Serial Bus). A telephone (for example, a feature phone or a smartphone) may also be the sound source. In this case, the player 10 outputs the voice signal input from the telephone during a call to the LSI 11 through the LSI 11.

[0018] The LSI 11 is an example of a computer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The CPU of the LSI 11 includes a single processor or a multiprocessor (in other words, at least one processor) that executes a program written in the ROM of the LSI 11, and controls the sound processing device 2 in an integrated manner.

[0019] The LSI 11 includes a plurality of speakers (in this embodiment, speakers SP FR , S.P. FL The interaural cross correlation function (IACF) is acquired when a sound output from the speakers is listened to at a predetermined listening position (for example, the driver's seat, the passenger seat, or the back seat), a target position is determined based on a predetermined range of the acquired interaural cross correlation functions, a delay amount is calculated based on the determined target position, and an audio signal, which is a sound signal and is output to at least one of the multiple speakers, is delayed based on the calculated delay amount. The predetermined range of the interaural cross correlation function is an interaural cross correlation function in a range of ±n (where n is a positive value exceeding 1) milliseconds (msec).

[0020] The audio signal after the time alignment process by the LSI 11 is converted to an analog signal by the D / A converter 12. This analog signal is amplified by the amplifier 13 and is output to the speaker SP FR , S.P. FL This allows, for example, music recorded on a sound source to be output to the speaker SP FR , S.P. FL It is played in the car cabin from

[0021] According to this embodiment, the delay amount is calculated using an interaural cross-correlation function in a wide range exceeding the range of ±1 millisecond (i.e., the range of ±n milliseconds) to perform time alignment processing, thereby improving the bias in sound image positioning that is likely to occur in a listening environment such as inside a vehicle.

[0022] In this embodiment, an in-vehicle sound processing system 1 is exemplified. However, bias in sound image localization may occur even in a listening environment such as the interior of a building. Therefore, the sound processing system 1 may be implemented in a listening environment other than the interior of a vehicle.

[0023] The display unit 14 is a device that displays various screens including a setting screen, and includes, for example, a display such as an LCD (Liquid Crystal Display), an organic EL (Electro Luminescence), etc. The display unit 14 may include a touch panel.

[0024] The operation unit 15 includes operators such as mechanical, capacitive non-contact, and membrane switches, buttons, knobs, and wheels. When the display unit 14 includes a touch panel, the touch panel also constitutes a part of the operation unit 15.

[0025] Fig. 3 is a functional block diagram of the sound processing system 1. The functions shown in each block in each functional block diagram including Fig. 3 are executed by cooperation between software and hardware included in the sound processing system 1.

[0026] As shown in FIG. 3, the sound processing system 1 includes a pre-processing unit 100 and a sound processing unit 200 as functional blocks.

[0027] The pre-processing unit 100 performs pre-processing for improving the bias of the sound image localization. As shown in FIG. 3, the pre-processing unit 100 includes an impulse response acquisition unit 101 and an impulse response recording unit .

[0028] Fig. 4 is a functional block diagram showing the impulse response acquisition unit 101. As shown in Fig. 4, the impulse response acquisition unit 101 includes, as functional blocks, a measurement signal generation unit 101a, a control unit 101b, and a response processing unit 101c.

[0029] The measurement signal generating unit 101a generates a predetermined measurement signal. The generated measurement signal is, for example, an M-sequence code (Maximal length sequence). The length of this measurement signal is set to be at least twice the code length. Note that the measurement signal may be another type of signal, such as a TSP signal (Time Stretched Pulse).

[0030] The control unit 101b outputs the measurement signal input from the measurement signal generating unit 101a to each speaker SP FR , S.P. FL In this way, a predetermined measurement sound is output to each speaker SP at a predetermined time interval. FR , S.P. FL are output in sequence.

[0031] In this embodiment, the measurement position of the impulse response (an example of a predetermined listening position) is the driver's seat. Therefore, the binaural microphone MIC is installed in the driver's seat. The installation position of the binaural microphone MIC changes depending on the listening position.

[0032] Microphone R and microphone MIC L First, the speaker FR This picks up the measurement sound output from the microphone MIC. R and microphone MIC L Then, the speaker SP FL The measurement sound output from is recorded.

[0033] The control unit 101b is a microphone MIC R , M.I.C. L The speaker outputs a signal of the measurement sound (i.e., a measurement signal) picked up by each of the speakers to the response processing unit 101c. FR The signal is output from the microphone MIC R The measurement signal picked up by R " is written. Speaker SP FL The signal is output from the microphone MIC R The measurement signal picked up by L " is written. Speaker SP FR The signal is output from the microphone MIC L The measurement signal picked up by the R " is written. Speaker SP FL The signal is output from the microphone MIC L The measurement signal picked up by the L " is written.

[0034] The response processor 101c acquires the impulse response.

[0035] For example, the response processing unit 101c receives the measurement signal R R The cross-correlation function between the reference measurement signal and the measurement signal R is calculated to calculate the impulse response. L The cross-correlation function between the measured signal and the reference signal is calculated to calculate an impulse response, and the two calculated impulse responses are then combined. The combined impulse response is the impulse response corresponding to the listener's right ear. Hereinafter, the impulse response corresponding to the listener's right ear will be referred to as "impulse response R'".

[0036] The response processing unit 101c receives the measurement signal L R The cross-correlation function between the reference measurement signal and the measurement signal L is calculated to calculate the impulse response. L The cross-correlation function between the measured signal and the reference signal is calculated to calculate an impulse response, and the two calculated impulse responses are then combined. The combined impulse response is the impulse response corresponding to the left ear of the listener. Hereinafter, the impulse response corresponding to the left ear of the listener will be referred to as "impulse response L'".

[0037] The reference measurement signal is the same as and time-synchronized with the measurement signal generated by the measurement signal generating unit 101a. The reference measurement signal is stored in the flash memory 16, for example.

[0038] The impulse response recording unit 102 writes the impulse responses R′ and L′ acquired by the impulse response acquisition unit 101 into, for example, the flash memory 16 .

[0039] As shown in FIG. 3, the acoustic processing unit 200 includes a band dividing unit 201, a calculation unit 202, an input unit 203, a band dividing unit 204, a processing unit 205, a band synthesis unit 206, and an output unit 207.

[0040] The band division unit 201 includes, for example, a 1 / N octave band filter. The band division unit 201 divides each of the impulse responses R′ and L′ written in the flash memory 16 into a plurality of bands bw1 to bwN using the 1 / N octave band filter, and outputs the bands to the calculation unit 202.

[0041] Hereinafter, the impulse response R' of each band after division is referred to as a "division band response Rd." Also, the impulse response L' of each band after division is referred to as a "division band response Ld."

[0042] The calculation unit 202 performs the processes of calculating an interaural cross-correlation function based on the divided band response Rd and the divided band response Ld, determining a target position based on the calculated interaural cross-correlation function, calculating a delay amount based on the target position, and calculating a phase correction amount for each band bw1 to bwN, thereby generating various control parameters. Details of each process performed by the calculation unit 202 will be described later.

[0043] The various control parameters generated by the calculation unit 202 include control parameters CPd and CPp corresponding to the bands bw1 to bwN. FR Audio signal output to speaker SP FL The control parameter CPp is a control parameter for delaying one of the audio signals output to the all-pass filter 10. The control parameter CPp is a control parameter for determining the amount of phase correction of the audio signal by the all-pass filter 10.

[0044] The input unit 203 includes a selector connected to various sound sources. The input unit 203 outputs an audio signal S1 input from the sound source connected to the selector to the band division unit 204.

[0045] In this embodiment, the audio signal S1 is an R channel audio signal S1 R and the L channel audio signal S1 L It is assumed that the signal is a two-channel signal including:

[0046] The band dividing unit 204 includes, for example, a 1 / N octave band filter. The band dividing unit 204 divides the audio signal S1 input from the input unit 203 into a plurality of bands bw1 to bwN using the 1 / N octave band filter in the same way as the band dividing unit 201, and outputs the bands to the processing unit 205.

[0047] The audio signal S1 of each band after division is R is "a split-band audio signal S2 R " Also, the audio signal S1 of each band after division is written as L is "a split-band audio signal S2 L " is written.

[0048] Fig. 5 is a functional block diagram showing the processing unit 205. As shown in Fig. 5, the processing unit 205 includes a delay processing unit 205a and a phase correction unit 205b.

[0049] The delay processing unit 205a delays the audio signal for each of the bands bw1 to bwN. For example, the delay processing unit 205a delays the divided band audio signal S2 input from the band division unit 204 based on the control parameter CPd input from the calculation unit 202 for each of the bands bw1 to bwN. R and the split-band audio signal S2 L One of these is delayed and output to the phase correction unit 205b.

[0050] The phase correction unit 205b corrects the phase of the audio signal for each of the bands bw1 to bwN. For example, the phase correction unit 205b includes an all-pass filter. As will be described in detail later, when the sign of the correlation value of the interaural cross-correlation function is negative, the phase correction unit 205b corrects the phase of the sub-band audio signal S2 based on the control parameter CPp input from the calculation unit 202. R and S2 L The phase of the sub-band audio signal S2 is corrected by applying an all-pass filter to the sub-band audio signal S2 and output to the band synthesis unit 206. When the sign of the correlation value of the interaural cross-correlation function is positive, the phase correction unit 205b corrects the phase of the sub-band audio signal S2 R and S2 LThe signal is output to the band synthesis unit 206 without being subjected to an all-pass filter.

[0051] Hereinafter, the sub-band audio signal S2 outputted from the phase correction unit 205b R is "the split-band audio signal S3 R ". Also, the sub-band audio signal S3 output from the phase correction unit 205b is written as ". L is "the split-band audio signal S3 L " is written.

[0052] The band synthesis unit 206 synthesizes the divided band audio signal S3 of the bands bw1 to bwN input from the phase correction unit 205b. R and the divided band audio signal S3 of the bands bw1 to bwN input from the phase correction unit 205b. L The sub-band audio signal S3 of the bands bw1 to bwN is synthesized. R R channel audio signal S4 R and the sub-band audio signal S3 of the bands bw1 to bwN L The L channel audio signal S4 is a composite of L is output to the output unit 207.

[0053] The output unit 207 receives the two-channel audio signal S4 from the band synthesis unit 206. R , S4 L are converted to analog signals, and the converted analog signals are amplified and output to the speaker SP FR , S.P. FL The delay processing unit 205a outputs the signal to the vehicle interior. This allows, for example, music from the sound source to be played back. The delay processing unit 205a executes time alignment processing based on the control parameter CPd, thereby improving the bias of the sound image localization during music playback.

[0054] Fig. 6 is a flowchart showing pre-processing executed by the pre-processing unit 100 according to an embodiment of the present invention. For example, when a predetermined touch operation is performed on the display unit 14 or a predetermined operation is performed on the operation unit 15, execution of the pre-processing shown in Fig. 6 is started. Note that, when executing the pre-processing, a binaural microphone MIC is placed at a listening position (for example, the driver's seat).

[0055] In the pre-processing shown in Fig. 6, the measurement signal generating unit 101a generates a predetermined measurement signal (step S101). The control unit 101b outputs the measurement signal to each speaker SP FR , S.P. FL The signals are sequentially output to the respective terminals (step S102).

[0056] The binaural microphone MIC is connected to each speaker SP FR , S.P. FL The measuring sounds sequentially output from the respective terminals are collected (step S103).

[0057] The control unit 101b controls a measurement signal (specifically, a measurement signal R R , R L , L R and L L ) to the response processing unit 101c.

[0058] The response processing unit 101c receives the measurement signal R R and R L and calculates an impulse response R' based on the measurement signal L input from the control unit 101b. R and L L (Step S104). The impulse response recording unit 102 writes the impulse responses R' and L' calculated by the response processing unit 101c to the flash memory 16 (Step S105).

[0059] 7 is a flowchart showing the acoustic processing executed by the acoustic processing unit 200 according to an embodiment of the present invention. For example, when the impulse responses R' and L' are written to the flash memory 16 by the impulse response recording unit 102, the execution of the acoustic processing shown in FIG.

[0060] 7, the band division unit 201 divides each of the impulse responses R′, L′ written in the flash memory 16 into a plurality of bands bw1 to bwN (step S201). The divided band responses Rd and Ld of each band after division are input to the calculation unit 202.

[0061] Fig. 8 is a functional block diagram showing the calculation unit 202. As shown in Fig. 8, the calculation unit 202 includes an IACF calculation unit 202a, a target position determination unit 202b, a delay amount calculation unit 202c, and a phase correction amount calculation unit 202d.

[0062] The IACF calculation unit 202a calculates an interaural cross-correlation function for each of the bands bw1 to bwN (step S202). For example, the IACF calculation unit 202a calculates the interaural cross-correlation function by the following equation.

[0063] (formula) TIFF2024001902000002.tif21162

[0064] Rd(t) indicates the amplitude of the sub-band response Rd at time t, and indicates the sound pressure entering the right ear at time t. Ld(t) indicates the amplitude of the sub-band response Ld of the same band as the sub-band response Rd at time t, and indicates the sound pressure entering the left ear at time t. t1 and t2 indicate measurement times. As an example, t1 is 0 milliseconds and t2 is 100 milliseconds. τ indicates correlation time. The range of the correlation time τ is a range exceeding ±1 millisecond, and is illustratively a range of ±50 milliseconds.

[0065] Fig. 9 is a diagram showing the interaural cross-correlation function calculated by IACF calculation section 202a. Fig. 9 shows, as an example, the interaural cross-correlation function in one of bands bw1 to bwN. In Fig. 9, the vertical axis indicates the correlation value, and the horizontal axis indicates the correlation time (unit: msec).

[0066] The closer the waveforms of the sounds that reach the right and left ears of the listener are, the closer the absolute value of the correlation value is to 1 in the binaural cross-correlation function illustrated in Fig. 9. If the sounds that reach the right and left ears of the listener are in phase, the correlation value is positive, and if the sounds that reach the right and left ears of the listener are in opposite phase, the correlation value is negative. The higher the absolute value of the correlation value, the stronger the sense of localization of the sound image, and the lower the absolute value of the correlation value, the weaker the sense of localization of the sound image.

[0067] In this embodiment, the correlation value is calculated based on the right ear. Therefore, if the sound image is on the right side of the listener, the correlation value with a high peak is likely to appear at a positive time. Also, if the sound image is on the left side of the listener, the correlation value with a high peak is likely to appear at a negative time. From this, in the example of FIG. 9, it is estimated that the sound image is localized slightly to the right of the listener.

[0068] In this way, the IACF calculation unit 202a calculates the IACF from multiple speakers (speakers SP FR , S.P. FL The function acquisition unit acquires the inter-ear cross-correlation function when the sound output from the earphones 10 and 11 is heard at a predetermined listening position (for example, the driver's seat, the passenger seat, or the back seat).

[0069] In this embodiment, in order to improve the sound image localization slightly biased to the right as illustrated in FIG. 9, the following processing is executed.

[0070] For example, the target position determining unit 202b determines the target position for each of the bands bw1 to bwN based on the interaural cross-correlation function calculated in step S202 (step S203).

[0071] Fig. 10 is a diagram in which symbols and the like for explaining a method for determining a target position are added to Fig. 9. Target position determination unit 202b calculates a center of gravity C of a binaural cross-correlation function within a predetermined range on a coordinate plane, as exemplified in Fig. 9, with the vertical axis representing the correlation value and the horizontal axis representing time.

[0072] The predetermined range of the interaural cross-correlation function is, for example, the interaural cross-correlation function in the range of ±30 milliseconds. The center of gravity C is the center of gravity of the entire figure formed by the interaural cross-correlation function in the range of ±30 milliseconds on the coordinate plane. The figure formed by the interaural cross-correlation function is the figure indicated by the hatched area (see FIG. 10) surrounded by the line of correlation value 0 and the graph of the interaural cross-correlation function.

[0073] The target position determining unit 202b determines the calculated center of gravity C as the target position.

[0074] In another embodiment, the target position determination unit 202b may determine, as the target position, a peak position of the interaural cross-correlation function near the center of gravity C. For example, the target position determination unit 202b may determine, as the target position, a peak position P1 closest to the center of gravity C, or may determine, as the target position, a peak position P2 that is the largest within a certain range (for example, a range of ±10 milliseconds around the center of gravity C).

[0075] In this way, the target position determination unit 202b operates as a position determination unit that determines the target position based on the interaural cross-correlation function within a predetermined range (range of ±n milliseconds) among the interaural cross-correlation functions acquired by the IACF calculation unit 202a. In addition, the target position determination unit 202b operates as a center of gravity calculation unit that calculates the center of gravity C of the interaural cross-correlation function within a predetermined range on a coordinate plane with the vertical axis representing the correlation value and the horizontal axis representing time, and determines the target position based on this center of gravity.

[0076] The delay amount calculation unit 202c calculates the amount of delay for each of the bands bw1 to bwN based on the target position determined by the target position determination unit 202b (step S204).

[0077] For example, the delay amount calculation unit 202c calculates the delay amount for the audio signal output to one speaker SP so that the center of gravity C, which is the target position, is located at or near 0 seconds on the time axis. C Since the delay appears at the position where the second is reached (in other words, slightly to the right of the listener), the delay amount calculation unit 202c calculates the delay amount from the speaker SP FR The delay for the audio signal output to the C Calculate seconds.

[0078] The delay amount calculation unit 202c generates, for each of the bands bw1 to bwN, a control parameter CPd for delaying the audio signal to be delayed (step S205).

[0079] The control parameter CPd includes values ​​indicating the delay target and the delay amount. In the example of FIG. 9 and FIG. 10, the speaker SP FR and the delay time T C A value indicating seconds is contained in the control parameter CPd.

[0080] When the target position is the peak position P1, the delay amount calculation unit 202c calculates the delay amount from the speaker SP FR The delay for the audio signal output to the P1 When the target position is the peak position P2, the delay amount calculation unit 202c calculates the delay time from the speaker SP FR The delay for the audio signal output to the P2 Calculate seconds.

[0081] The acoustic processing unit 200 executes a time alignment process based on the control parameter CPd (step S206).

[0082] Specifically, the delay processing unit 205a of the processing unit 205 executes delay processing based on the control parameter CPd for each of the bands bw1 to bwN. Then, the band synthesis unit 206 executes band synthesis processing and the output unit 207 executes output processing, and audio signals that have been subjected to time alignment processing for each of the bands bw1 to bwN are reproduced.

[0083] In this way, the delay processing unit 205a operates as a delay unit that delays the audio signal to be output to at least one of the multiple speakers, based on the amount of delay calculated by the delay amount calculation unit 202c.

[0084] In the pre-processing unit 100, impulse responses R' and L' of the sound after the time alignment process, which is output from the output unit 207, are calculated and written into the flash memory 16 (see steps S103 to S106 in FIG. 6).

[0085] The band division unit 201 divides each of the impulse responses R' and L' of the time-aligned sound written in the flash memory 16 into a plurality of bands bw1 to bwN (step S207). The IACF calculation unit 202a calculates the interaural cross-correlation function of the impulse responses R' and L' of the time-aligned sound for each of the bands bw1 to bwN (step S208).

[0086] FIG. 11 is a diagram showing an example of the interaural cross-correlation function calculated by the IACF calculation unit 202a in step S208.

[0087] As shown in Fig. 11, by executing a time alignment process based on the control parameter CPd, the center of gravity C of the interaural cross-correlation function in a predetermined range (range of ±30 milliseconds) moves to a position near 0 seconds on the time axis. In the example of Fig. 11, since the center of gravity C with a strong sense of sound image localization is located near 0 seconds on the time axis, it can be seen that the bias of sound image localization has been improved.

[0088] In this embodiment, the target position is not determined by a simple method such as determining the highest peak position as the target position, but is determined based on the center of gravity taking into consideration correlation values ​​other than the peak position (in other words, values ​​that affect the sense of localization of the sound image). Therefore, even in a listening environment such as a car interior where the speaker arrangement is asymmetric and there is a lot of reflected sound and reverberation, the graph of the interaural cross-correlation function can have a complex shape, the effect of improving the bias of the sound image localization can be sufficiently obtained.

[0089] Here, if the sign of the correlation value with the largest absolute value among the binaural cross-correlation functions within the predetermined range calculated in step S208 is negative, the speaker SP FR Sound from and speaker SP FL The phase of the sound from the other side is reversed, which causes the listener to feel uncomfortable.

[0090] Therefore, when the sign of the largest correlation value is negative (step S209: YES), the phase correction amount calculation unit 202d generates a control parameter CPp for making the sign of this correlation value positive (step S210). When the sign of the largest correlation value is positive (step S209: NO), the acoustic processing shown in FIG. 7 ends.

[0091] The control parameter CPp includes a value indicating a phase correction amount, which indicates, for example, a value for rotating the phase of the band to be processed, among the bands bw1 to bwN, by 180 degrees.

[0092] The acoustic processing unit 200 executes a phase correction process based on the control parameter CPp (step S211).

[0093] Specifically, the phase correction unit 205b of the processing unit 205 executes a phase correction process based on the control parameter CPp by an all-pass filter for each of the bands bw1 to bwN. The all-pass filter applied in the phase correction process is, for example, a cascade connection of a predetermined number of second-order IIR (Infinite Impulse Response) filters. The number of second-order IIR filters is appropriately determined in consideration of the accuracy of the phase correction and the filter processing load.

[0094] The phase correction unit 205b performs phase correction processing to correct the phase of the speaker SP FR Sound from and speaker SP FL Since the phase of the sound from the receiver is aligned, music and other content is reproduced with a natural sound that sounds natural to the ear.

[0095] The above is a description of exemplary embodiments of the present invention. The embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical idea of ​​the present invention. For example, the embodiments of the present application also include appropriate combinations of the embodiments, etc., which are exemplified in the specification, or obvious embodiments, etc.

[0096] For example, in the above embodiment, the calculation and recording of the impulse responses R' and L' are executed as pre-processing for improving the bias of the sound image localization, but the present invention is not limited to this. In another embodiment, in addition to the calculation and recording of the impulse responses R' and L', band division by the band division unit 201 and various processes by the calculation unit 202 (calculation of the interaural cross-correlation function, determination of the target position, calculation of the delay amount, calculation of the phase correction amount, and generation of the control parameters) may be executed as pre-processing.

[0097] Speaker SP FR and SP FL In addition, if a pair of speakers is installed on the rear seat side, the process is executed in the following procedure. For example, a binaural microphone MIC is installed on the front seat (driver's seat or passenger seat) and a speaker SP FR and SP FL6 and 7 are executed for the pair of speakers on the rear seat side. Next, a binaural microphone MIC is installed in the rear seat, and the processes shown in Fig. 6 and 7 are executed for the pair of speakers on the rear seat side. [Explanation of symbols]

[0098] 1: Sound processing system 2: Sound processing device 100: Pre-processing section 200: Sound processing section

Claims

1. a function acquisition unit that acquires an interaural cross-correlation function when sounds output from a plurality of speakers are listened to at a predetermined listening position; a position determination unit that determines a target position based on a predetermined range of the interaural cross-correlation functions acquired by the function acquisition unit; a delay amount calculation unit that calculates a delay amount based on the target position determined by the position determination unit; a delay unit that delays an audio signal, which is a signal of the sound, and is output to at least one speaker among the plurality of speakers, based on the delay amount calculated by the delay amount calculation unit. Sound processing system.

2. a center of gravity calculation unit that calculates a center of gravity of the interaural cross-correlation function in the predetermined range on a coordinate plane with the vertical axis being the correlation value and the horizontal axis being time, The position determination unit determines the target position based on the center of gravity of the interaural cross-correlation function calculated by the center of gravity calculation unit. The sound processing system of claim 1 .

3. The target position is a center of gravity of the interaural cross-correlation function of the predetermined range or a peak position of the interaural cross-correlation function near the center of gravity. The sound processing system of claim 2 .

4. when a sign of a correlation value that is a peak of the interaural cross-correlation function after the delay process on the audio signal by the delay unit is negative, correcting a phase of the audio signal so that the sign of the correlation value becomes positive. The sound processing system according to claim 2 or 3.

5. the function acquisition unit acquires the interaural cross-correlation function corresponding to each of a plurality of bands, determining the target position by the position determination unit, calculating the delay amount by the delay amount calculation unit, and executing a delay process on the audio signal by the delay unit, for each of the plurality of bands; The sound processing system according to any one of claims 1 to 3.

6. A binaural cross-correlation function is obtained when sounds output from a plurality of speakers are listened to at a predetermined listening position, determining a target position based on a predetermined range of the interaural cross-correlation functions among the acquired interaural cross-correlation functions; Calculating a delay amount based on the determined target position; a delaying step of delaying an audio signal, which is a sound signal and is to be output to at least one of the plurality of speakers, based on the calculated delay amount; Acoustic processing methods.

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