# US 11,451,921 B2 · Audio processing method and apparatus

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- Number: US 11,451,921 B2
- Document ID: US11451921B2
- Status: Granted
- Kind: B2
- Application number: 17/179,619
- Filed: 2021-02-19
- Published: 2021-06-10
- Granted: 2022-09-20
- Earliest claimed: 2018-08-20
- Assignees: Huawei Technologies Co., Ltd.
- Applicants: Huawei Technologies Co., Ltd.
- Inventors: Gavin Kearney; Cal Armstrong; Bin Wang; Zexin Liu
- Web page: https://patentgrep.com/patent/US11451921B2

## CPC

- H04S 7/302: {Electronic adaptation of stereophonic sound system to listener position or orientation (H04S7/301 takes precedence)}
- H04S 7/303: {Tracking of listener position or orientation}
- H04R 5/04: Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)}
- H04S 7/305: {Electronic adaptation of stereophonic audio signals to reverberation of the listening space (H04S7/301 takes precedence)}
- H04S 2400/01: Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
- H04S 2400/11: Positioning of individual sound objects, e.g. moving airplane, within a sound field (H04S2420/13 takes precedence)
- H04S 2420/01: Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
- H04S 2420/07: Synergistic effects of band splitting and sub-band processing
- H04S 2420/11: Application of ambisonics in stereophonic audio systems
- H04S: STEREOPHONIC SYSTEMS
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

An audio processing method includes: M audio signals are obtained by processing an audio signal by M virtual speakers; M first HRTFs and M second HRTFs are obtained, where the M first HRTFs corresponding to a left ear position, and the M second HRTFs corresponding to a right ear position; high-band impulse responses of some of the M first HRTFs are modified to obtain modified first target HRTFs, and high-band impulse responses of some of the M second HRTFs are modified to obtain modified second target HRTFs; a first target audio signal corresponding to the left ear position is obtained based on the modified first target HRTFs and un-modified first HRTFs, and the M audio signals; and a second target audio signal corresponding to the right ear position is obtained based on the modified second HRTFs, un-modified second target HRTFs, and the M audio signals.

## Claims

### Claim 1

An audio processing method, comprising:
obtaining M first audio signals by processing an audio signal by M virtual speakers corresponding to the M first audio signals respectively, wherein M is a positive integer;
obtaining M first head-related transfer functions (HRTFs) to which the M first audio signals correspond from the M virtual speakers to a left ear position, the M first HRTFs corresponding to the M virtual speakers respectively;
obtaining M second HRTFs to which the M first audio signals correspond from the M virtual speakers to a right ear position, the M second HRTFs corresponding to the M virtual speakers respectively;
modifying high-band impulse responses of a first quantity of first HRTFs to obtain a first quantity of first target HRTFs, wherein the first quantity is not less than 1 and not greater than M;
modifying high-band impulse responses of a second quantity of second HRTFs, to obtain a second quantity of second target HRTFs, wherein the second quantity is not less than 1 and not greater than M;
obtaining, based on the first quantity of the first target HRTFs, a third quantity of first HRTFs, and the M first audio signals, a first target audio signal corresponding to a current left ear position, wherein the third quantity of first HRTFs are HRTFs other than the first quantity of first HRTFs in the M first HRTFs, a sum of the first quantity and the third quantity is equal to M; and
obtaining, based on a fourth quantity of second HRTFs, the second quantity of second target HRTFs, and the M first audio signals, a second target audio signal corresponding to a current right ear position, the fourth quantity of second HRTFs are HRTFs other than the second quantity of second HRTFs in the M second HRTFs, and a sum of the second quantity and the fourth quantity is equal to M.

### Claim 2 (depends on 1)

The method according to claim 1, wherein correspondences between a plurality of preset positions and a plurality of HRTFs are prestored, and the obtaining M first HRTFs comprises:
obtaining M first positions of the M virtual speakers relative to the current left ear position; and
determining, based on the M first positions and the correspondences between the preset positions and the HRTFs, that M HRTFs corresponding to the M first positions are the M first HRTFs;
or
the obtaining M second HRTFs comprises:
obtaining M second positions of the M virtual speakers relative to the current right ear position; and
determining, based on the M second positions and the correspondences between the preset positions and the HRTFs, that M HRTFs corresponding to the M second positions are the M second HRTFs.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the obtaining a first target audio signal corresponding to the current left ear position comprises:
convolving each of the M first audio signals with a corresponding HRTF in all HRTFs of the first quantity of first target HRTFs and the third quantity of first HRTFs to obtain M first convolved audio signals; and
obtaining the first target audio signal based on the M first convolved audio signals;
or
wherein the obtaining a second target audio signal corresponding to the current right ear position comprises:
convolving each of the M first audio signals with a corresponding HRTF in all HRTFs of the fourth quantity of second HRTFs and the second quantity of second target HRTFs to obtain M second convolved audio signals; and
obtaining the second target audio signal based on the M second convolved audio signals.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the first quantity of first HRTFs corresponds to a first quantity of virtual speakers located on a first side of a target center that is far away from the current left ear position, and the target center is a center of three-dimensional space corresponding to the M virtual speakers.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the modifying high-band impulse responses of a first quantity of first HRTFs to obtain a first quantity of first target HRTFs comprises:
multiplying a first modification factor and the high-band impulse responses comprised in the first quantity of first HRTFs to obtain the first quantity of first target HRTFs, wherein the first modification factor is greater than 0 and less than 1;
or
wherein the modifying high-band impulse responses of a first quantity of first HRTFs, to obtain a first quantity of first target HRTFs comprises:
multiplying a first modification factor and the high-band impulse responses comprised in the first quantity of first HRTFs to obtain a first quantity of third target HRTFs, wherein the first modification factor is a value greater than 0 and less than 1; and
multiplying a third modification factor and each impulse response comprised in the first quantity of third target HRTFs to obtain the first quantity of first target HRTFs, wherein the third modification factor is a value greater than 1;
or
multiplying a first modification factor and the high-band impulse responses comprised in the first quantity of first HRTFs to obtain a first quantity of third target HRTFs, wherein the first modification factor is a value greater than 0 and less than 1; and
for at least one third target HRTF, multiplying a first value and all impulse responses comprised in the at least one third target HRTF to obtain a first target HRTF corresponding to the at least one third target HRTF, wherein the first value is a ratio of a first sum of squares to a second sum of squares, the first sum of squares is a sum of squares of all impulse responses comprised in a first HRTF corresponding to the at least one third target HRTF, and the second sum of squares is a sum of squares of all impulse responses comprised in the at least one third target HRTF.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the second quantity of second HRTFs corresponds to a second quantity of virtual speakers located on a second side of a target center that is far away from the current right ear position, and the target center is a center of a three-dimensional space corresponding to the M virtual speakers.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the modifying high-band impulse responses of a second quantity of second HRTFs to obtain a second quantity of second target HRTFs comprises:
multiplying a second modification factor and the high-band impulse responses comprised in the second quantity of second HRTFs to obtain the second quantity of second target HRTFs, wherein the second modification factor is a value greater than 0 and less than 1;
or
wherein the modifying high-band impulse responses of a second quantity of second HRTFs, to obtain a second quantity of second target HRTFs comprises:
multiplying a second modification factor and the high-band impulse responses comprised in the second quantity of second HRTFs to obtain a second quantity of fourth target HRTFs, wherein the second modification factor is a value greater than 0 and less than 1; and
multiplying a fourth modification factor and each impulse response comprised in the second quantity of fourth target HRTFs to obtain the second quantity of second target HRTFs, wherein the fourth modification factor is a value greater than 1;
or
multiplying a second modification factor and the high-band impulse responses comprised in the second quantity of second HRTFs to obtain the second quantity of fourth target HRTFs, wherein the second modification factor is a value greater than 0 and less than 1; and
for at least one fourth target HRTF, multiplying a second value and all impulse responses comprised in the at least one fourth target HRTF to obtain a second target HRTF corresponding to the at least one fourth target HRTF, wherein the second value is a ratio of a third sum of squares to a fourth sum of squares, the third sum of squares is a sum of squares of all impulse responses comprised in a second HRTF corresponding to the at least one fourth target HRTF, and the fourth sum of squares is a sum of squares of all impulse responses comprised in the at least one fourth target HRTF.

### Claim 8 (depends on 1)

The method according to claim 1, wherein a first quantity is equal to a1+a2, a1 first HRTFs correspond to a1 virtual speakers located on a first side of a target center that is far away from the current left ear position, a2 first HRTFs correspond to a2 virtual speakers located on a second side of a target center that is far away from the current right ear position, and the target center is a center of three-dimensional space corresponding to the M virtual speakers.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the modifying high-band impulse responses of a first quantity of first HRTFs to obtain a first quantity of first target HRTFs comprises:
multiplying a first modification factor and high-band impulse responses of the a1 first HRTFs to obtain a1 third target HRTFs, and multiplying a fifth modification factor and high-band impulse responses of the a2 first HRTFs to obtain a2 fifth target HRTFs, wherein the first quantity of first target HRTFs comprise the a1 third target HRTFs and the a2 fifth target HRTFs; wherein
a product of the first modification factor and the fifth modification factor is 1, and the first modification factor is a value greater than 0 and less than 1;
or
wherein the modifying high-band impulse responses of a first quantity of first HRTFs to obtain a first quantity of first target HRTFs comprises:
multiplying a first modification factor and high-band impulse responses of the a1 first HRTFs to obtain a1 third target HRTFs, and multiplying a fifth modification factor and high-band impulse responses of the a2 first HRTFs to obtain a2 fifth target HRTFs, wherein a product of the first modification factor and the fifth modification factor is 1, and the first modification factor is a value greater than 0 and less than 1; and
multiplying a third modification factor and each impulse response comprised in the a1 third target HRTFs to obtain at sixth target HRTFs, and multiplying a sixth modification factor and each impulse response comprised in the a2 fifth target HRTFs to obtain a2 seventh target HRTFs, wherein the first quantity of first target HRTFs comprise the a1 sixth target HRTFs and the a2 seventh target HRTFs, the third modification factor is a value greater than 1, and the sixth modification factor is a value greater than 0 and less than 1;
or
multiplying a first modification factor and high-band impulse responses of the a1 first HRTFs to obtain a1 third target HRTFs, and multiplying a fifth modification factor and high-band impulse responses of the a2 first HRTFs to obtain a2 fifth target HRTFs, wherein a product of the first modification factor and the fifth modification factor is 1, and the first modification factor is a value greater than 0 and less than 1; and
for at least one third target HRTF, multiplying a first value and all impulse responses comprised in the at least one third target HRTF to obtain a sixth target HRTF corresponding to the at least one third target HRTF, wherein the first value is a ratio of a first sum of squares to a second sum of squares, the first sum of squares is a sum of squares of all impulse responses comprised in a first HRTF corresponding to the at least one third target HRTF, and the second sum of squares is a sum of squares of all impulse responses comprised in the at least one third target HRTF; and
for at least one fifth target HRTF, multiplying a third value and all impulse responses comprised in the one fifth target HRTF to obtain a seventh target HRTF corresponding to the at least one fifth target HRTF, wherein the third value is a ratio of a fifth sum of squares to a sixth sum of squares, the fifth sum of squares is a sum of squares of all impulse responses comprised in a first HRTF corresponding to the at least one fifth target HRTF, and the sixth sum of squares is a sum of squares of all impulse responses comprised in the at least one fifth target HRTF; and the first quantity of first target HRTFs comprise a1 sixth target HRTFs and a2 seventh target HRTFs.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the second quantity is equal to a sum of b1 and b2, b1 second HRTFs correspond to b1 virtual speakers located on a second side of a target center that is far away from the current right ear position, b2 second HRTFs correspond to b2 virtual speakers located on a first side of the target center that is far away from the current left ear position, and the target center is a center of a three-dimensional space corresponding to the M virtual speakers.

### Claim 11 (depends on 10)

The method according to claim 10, wherein the modifying high-band impulse responses of a second quantity of second HRTFs to obtain a second quantity of second target HRTFs comprises:
multiplying a second modification factor and high-band impulse responses of the b1 second HRTFs to obtain b1 fourth target HRTFs, and multiplying a seventh modification factor and high-band impulse responses of the b2 second HRTFs to obtain b2 eighth target HRTFs, wherein the second quantity of second target HRTFs comprise the b1 fourth target HRTFs and the b2 eighth target HRTFs; wherein
a product of the second modification factor and the seventh modification factor is 1, and the second modification factor is a value greater than 0 and less than 1;
or
wherein the modifying high-band impulse responses of a second quantity of second HRTFs to obtain a second quantity of second target HRTFs comprises:
multiplying a second modification factor and high-band impulse responses of the b1 second HRTFs to obtain b1 fourth target HRTFs, and multiplying a seventh modification factor and high-band impulse responses of the b2 second HRTFs to obtain b2 eighth target HRTFs, wherein a product of the second modification factor and the seventh modification factor is 1, and the second modification factor is a value greater than 0 and less than 1; and
multiplying a fourth modification factor and each impulse response comprised in the b1 fourth target HRTFs to obtain b1 ninth target HRTFs, and multiplying an eighth modification factor and each impulse response comprised in the b2 eighth target HRTFs to obtain b2 tenth target HRTFs, wherein the second quantity of second target HRTFs comprise the b1 ninth target HRTFs and the b2 tenth target HRTFs, the fourth modification factor is a value greater than 1, and the eighth modification factor is a value greater than 0 and less than 1;
or
multiplying a second modification factor and high-band impulse responses of the b1 second HRTFs to obtain b1 fourth target HRTFs, and multiplying a seventh modification factor and high-band impulse responses of the b2 second HRTFs to obtain b2 eighth target HRTFs, wherein a product of the second modification factor and the seventh modification factor is 1, and the second modification factor is a value greater than 0 and less than 1; and
for at least one fourth target HRTF, multiplying a second value and all impulse responses comprised in the at least one fourth target HRTF to obtain a ninth target HRTF corresponding to the at least one fourth target HRTF, wherein the second value is a ratio of a third sum of squares to a fourth sum of squares, the third sum of squares is a sum of squares of all impulse responses comprised in a second HRTF corresponding to the at least one fourth target HRTF, and the fourth sum of squares is a sum of squares of all impulse responses comprised in the at least one fourth target HRTF; and
for at least one eighth target HRTF, multiplying a fourth value and all impulse responses comprised in the at least one eighth target HRTF, to obtain a tenth target HRTF corresponding to the at least one eighth target HRTF, wherein the fourth value is a ratio of a seventh sum of squares to an eighth sum of squares, the seventh sum of squares is a sum of squares of all impulse responses comprised in a second HRTF corresponding to the at least one eighth target HRTF, and the eighth sum of squares is a sum of squares of all impulse responses comprised in the at least one eighth target HRTF; and the second quantity of second target HRTFs comprise b1 ninth target HRTFs and b2 tenth target HRTFs.

### Claim 12 (depends on 1)

The method according to claim 1, further comprising:
adjusting an order of magnitude of energy of the first target audio signal to a first order of magnitude of energy of a third target audio signal, and the third target audio signal is obtained based on the M first HRTFs and the M first audio signals; and
adjusting an order of magnitude of energy of the second target audio signal to a second order of magnitude of energy of a fourth target audio signal, and the fourth target audio signal is obtained based on the M second HRTFs and the M first audio signals.

### Claim 13

An audio processing apparatus, comprising:
at least one processor; and
a memory storing computer executable instructions for execution by the at least one processor, wherein the computer executable instructions instruct the at least one processor to:
obtain M first audio signals by processing an audio signal by M virtual speakers corresponding to the M first audio signals respectively, wherein M is a positive integer;
obtain M first head-related transfer functions (HRTFs) corresponding to the M first audio signals respectively from the M virtual speakers to a left ear position;
obtain M second HRTFs corresponding to the M first audio signals respectively from the M virtual speakers to a right ear position;
modify high-band impulse responses of a first quantity of first HRTFs to obtain a first quantity of first target HRTFs, wherein the first quantity is not less than 1 and not greater than M;
modify high-band impulse responses of a second quantity of second HRTFs to obtain a second quantity of second target HRTFs, wherein the second quantity is not less than 1 and not greater than M;
obtain, based on the first quantity of first target HRTFs, the third quantity of first HRTFs, and the M first audio signals, a first target audio signal corresponding to a current left ear position, wherein the third quantity of first HRTFs are HRTFs other than the first quantity of first HRTFs in the M first HRTFs, a sum of the first quantity and the third quantity is M; and
obtain, based on a fourth quantity of second HRTFs, the second quantity of second target HRTFs, and the M first audio signals, a second target audio signal corresponding to a current right ear position, the fourth quantity of second HRTFs are HRTFs other than the second quantity of second HRTFs in the M second HRTFs, and a sum of the second quantity and the fourth quantity is equal to M.

### Claim 14 (depends on 13)

The apparatus according to claim 13, wherein correspondences between a plurality of preset positions and a plurality of HRTFs are prestored, and wherein the computer executable instructions further instruct the at least one processor to:
obtain M first positions of the M virtual speakers relative to the current left ear position; and
determine, based on the M first positions and correspondences between the preset positions and the HRTFs, that M HRTFs corresponding to the M first positions are the M first HRTFs;
or
obtain M second positions of the M virtual speakers relative to the current right ear position; and
determine, based on the M second positions and correspondences between the preset positions and the HRTFs, that M HRTFs corresponding to the M second positions are the M second HRTFs.

### Claim 15 (depends on 13)

The apparatus according to claim 13, wherein the computer executable instructions further instruct the at least one processor to:
convolve each of the M first audio signals with a corresponding HRTF in all HRTFs of the first quantity of first target HRTFs and the third quantity of first HRTFs to obtain M first convolved audio signals; and
obtain the first target audio signal based on the M first convolved audio signals;
or
convolve each of the M first audio signals with a corresponding HRTF in all HRTFs of the fourth quantity of second HRTFs and the second quantity of second target HRTFs to obtain M second convolved audio signals; and
obtain the second target audio signal based on the M second convolved audio signals.

### Claim 16 (depends on 13)

The apparatus according to claim 13, wherein the first quantity of first HRTFs corresponds to a first quantity of virtual speakers located on a first side of a target center that is far away from the current left ear position, wherein the target center is a center of three-dimensional space corresponding to the M virtual speakers.

### Claim 17 (depends on 16)

The apparatus according to claim 16, wherein the computer executable instructions further instruct the at least one processor to:
multiply a first modification factor and the high-band impulse responses comprised in the first quantity of first HRTFs to obtain the first quantity of first target HRTFs, wherein the first modification factor is greater than 0 and less than 1;
or
multiply a first modification factor and the high-band impulse responses comprised in the first quantity of first HRTFs to obtain a first quantity of third target HRTFs, wherein the first modification factor is a value greater than 0 and less than 1; and
multiply a third modification factor and each impulse response comprised in the first quantity of third target HRTFs to obtain the first quantity of first target HRTFs, wherein the third modification factor is a value greater than 1;
or
multiply a first modification factor and the high-band impulse responses comprised in the first quantity of first HRTFs, to obtain a first quantity of third target HRTFs, wherein the first modification factor is a value greater than 0 and less than 1; and
for at least one third target HRTF, multiply a first value and all impulse responses comprised in the at least one third target HRTF, to obtain a first target HRTF corresponding to the at least one third target HRTF, wherein the first value is a ratio of a first sum of squares to a second sum of squares, the first sum of squares is a sum of squares of all impulse responses comprised in a first HRTF corresponding to the at least one third target HRTF, and the second sum of squares is a sum of squares of all impulse responses comprised in the at least one third target HRTF.

### Claim 18 (depends on 13)

The apparatus according to claim 13, wherein the second quantity of second HRTFs corresponds to a second quantity of virtual speakers located on a second side of a target center that is far away from the current right ear position, wherein the target center is a center of a three-dimensional space corresponding to the M virtual speakers.

### Claim 19 (depends on 18)

The apparatus according to claim 18, wherein the computer executable instructions further instruct the at least one processor to:
multiply a second modification factor and the high-band impulse responses comprised in the second quantity of second HRTFs to obtain the second quantity of second target HRTFs, wherein the second modification factor is a value greater than 0 and less than 1;
or
multiply a second modification factor and the high-band impulse responses comprised in the second quantity of second HRTFs to obtain the second quantity of fourth target HRTFs, wherein the second modification factor is a value greater than 0 and less than 1; and
multiply a fourth modification factor and each impulse response comprised in the second quantity of fourth target HRTFs to obtain the second quantity of second target HRTFs, wherein the fourth modification factor is a value greater than 1;
or
multiply a second modification factor and the high-band impulse responses comprised in the second quantity of second HRTFs to obtain the second quantity of fourth target HRTFs, wherein the second modification factor is a value greater than 0 and less than 1; and
for at least one fourth target HRTF, multiply a second value and all impulse responses comprised in the at least one fourth target HRTF, to obtain a second target HRTF corresponding to the at least one fourth target HRTF, wherein the second value is a ratio of a third sum of squares to a fourth sum of squares, the third sum of squares is a sum of squares of all impulse responses comprised in a second HRTF corresponding to the at least one fourth target HRTF, and the fourth sum of squares is a sum of squares of all impulse responses comprised in the at least one fourth target HRTF.

### Claim 20 (depends on 13)

The apparatus according to claim 13, wherein the first quantity is equal to a sum of a1 and a2, a1 first HRTFs correspond to a1 virtual speakers located on a first side of a target center that is far away from the current left ear position, wherein a2 first HRTFs correspond to a2 virtual speakers located on a second side of the target center that is far away from the current right ear position, and wherein the target center is a center of three-dimensional space corresponding to the M virtual speakers.

### Claim 21 (depends on 20)

The apparatus according to claim 20, wherein the computer executable instructions further instruct the at least one processor to:
multiply a first modification factor and high-band impulse responses of the a1 first HRTFs to obtain a1 third target HRTFs, and multiply a fifth modification factor and high-band impulse responses of the a2 first HRTFs to obtain a2 fifth target HRTFs, wherein the first quantity of first target HRTFs comprise the a1 third target HRTFs and the a2 fifth target HRTFs, wherein
a product of the first modification factor and the fifth modification factor is 1, and the first modification factor is a value greater than 0 and less than 1;
or
multiply a first modification factor and high-band impulse responses of the a1 first HRTFs to obtain a1 third target HRTFs, and multiply a fifth modification factor and high-band impulse responses of the a2 first HRTFs to obtain a2 fifth target HRTFs, wherein a product of the first modification factor and the fifth modification factor is 1, and the first modification factor is a value greater than 0 and less than 1; and
multiply a third modification factor and each impulse response comprised in the a1 third target HRTFs to obtain a1 sixth target HRTFs, and multiply a sixth modification factor and each impulse response comprised in the a2 fifth target HRTFs to obtain a2 seventh target HRTFs, wherein the first quantity of first target HRTFs comprise the a1 sixth target HRTFs and the a2 seventh target HRTFs, the third modification factor is a value greater than 1, and the sixth modification factor is a value greater than 0 and less than 1;
or
multiply a first modification factor and high-band impulse responses of the a1 first HRTFs to obtain a1 third target HRTFs, and multiply a fifth modification factor and high-band impulse responses of the a2 first HRTFs to obtain a2 fifth target HRTFs, wherein a product of the first modification factor and the fifth modification factor is 1, and the first modification factor is a value greater than 0 and less than 1; and
for at least one third target HRTF, multiply a first value and all impulse responses comprised in the at least one third target HRTF, to obtain a sixth target HRTF corresponding to the at least one third target HRTF, wherein the first value is a ratio of a first sum of squares to a second sum of squares, the first sum of squares is a sum of squares of all impulse responses comprised in a first HRTF corresponding to the at least one third target HRTF, and the second sum of squares is a sum of squares of all impulse responses comprised in the at least one third target HRTF; and
for at least one fifth target HRTF, multiply a third value and all impulse responses comprised in the at least one fifth target HRTF, to obtain a seventh target HRTF corresponding to the at least one fifth target HRTF, wherein the third value is a ratio of a fifth sum of squares to a sixth sum of squares, the fifth sum of squares is a sum of squares of all impulse responses comprised in a first HRTF corresponding to the at least one fifth target HRTF, and the sixth sum of squares is a sum of squares of all impulse responses comprised in the at least one fifth target HRTF; and the first quantity of first target HRTFs comprise a1 sixth target HRTFs and a2 seventh target HRTFs.

### Claim 22 (depends on 13)

The apparatus according to claim 13, wherein the second quantity is equal to a sum of b1 and b2, b1 second HRTFs correspond to b1 virtual speakers located on a second side of a target center that is far away from the current left ear position, b2 second HRTFs correspond to b2 virtual speakers located on a first side of the target center that is far away from the current right ear position, wherein the target center is a center of a three-dimensional space corresponding to the M virtual speakers.

### Claim 23 (depends on 22)

The apparatus according to claim 22, wherein the computer executable instructions further instruct the at least one processor to:
multiply a second modification factor and high-band impulse responses of the b1 second HRTFs to obtain b1 fourth target HRTFs, and multiply a seventh modification factor and high-band impulse responses of the b2 second HRTFs to obtain b2 eighth target HRTFs, wherein the second quantity of second target HRTFs comprise the b1 fourth target HRTFs and the b2 eighth target HRTFs; wherein
a product of the second modification factor and the seventh modification factor is 1, and the second modification factor is a value greater than 0 and less than 1;
or
multiply a second modification factor and high-band impulse responses of the b1 second HRTFs to obtain b1 fourth target HRTFs, and multiply a seventh modification factor and high-band impulse responses of the b2 second HRTFs to obtain b2 eighth target HRTFs, wherein a product of the second modification factor and the seventh modification factor is 1, and the second modification factor is a value greater than 0 and less than 1; and
multiply a fourth modification factor and each impulse response comprised in the b1 fourth target HRTFs to obtain b1 ninth target HRTFs, and multiply an eighth modification factor and each impulse response comprised in the b2 eighth target HRTFs to obtain b2 tenth target HRTFs, wherein the second quantity of second target HRTFs comprise the b1 ninth target HRTFs and the b2 tenth target HRTFs, the fourth modification factor is a value greater than 1, and the eighth modification factor is a value greater than 0 and less than 1;
or
multiply a second modification factor and high-band impulse responses of the b1 second HRTFs to obtain b1 fourth target HRTFs, and multiply a seventh modification factor and high-band impulse responses of the b2 second HRTFs to obtain b2 eighth target HRTFs, wherein a product of the second modification factor and the seventh modification factor is 1, and the second modification factor is a value greater than 0 and less than 1; and
for at least one fourth target HRTF, multiply a second value and all impulse responses comprised in the at least one fourth target HRTF, to obtain a ninth target HRTF corresponding to the at least one fourth target HRTF, wherein the second value is a ratio of a third sum of squares to a fourth sum of squares, the third sum of squares is a sum of squares of all impulse responses comprised in a second HRTF corresponding to the at least one fourth target HRTF, and the fourth sum of squares is a sum of squares of all impulse responses comprised in the at least one fourth target HRTF; and
for at least one eighth target HRTF, multiply a fourth value and all impulse responses comprised in the at least one eighth target HRTF, to obtain a tenth target HRTF corresponding to the at least one eighth target HRTF, wherein the fourth value is a ratio of a seventh sum of squares to an eighth sum of squares, the seventh sum of squares is a sum of squares of all impulse responses comprised in a second HRTF corresponding to the at least one eighth target HRTF, and the eighth sum of squares is a sum of squares of all impulse responses comprised in the at least one eighth target HRTF; and the second quantity of second target HRTFs comprise b1 ninth target HRTFs and b2 tenth target HRTFs.

### Claim 24 (depends on 13)

The apparatus according to claim 13, wherein the computer executable instructions further instruct the at least one processor to:
adjust an order of magnitude of energy of the first target audio signal to a first order of magnitude of energy of a third target audio signal, and the third target audio signal is obtained based on the M first HRTFs and the M first audio signals; and
adjust an order of magnitude of energy of the second target audio signal to a second order of magnitude of energy of a fourth target audio signal, and the fourth target audio signal is obtained based on the M second HRTFs and the M first audio signals.