# US 12,223,978 B2 · Audio system

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- Number: US 12,223,978 B2
- Document ID: US12223978B2
- Status: Granted
- Kind: B2
- Application number: 17/973,651
- Filed: 2022-10-26
- Published: 2023-05-18
- Granted: 2025-02-11
- Earliest claimed: 2021-11-12
- Assignees: Alps Alpine Co., Ltd.
- Applicants: Alps Alpine Co., LTD.
- Inventors: Nozomu Saito; Keita Tanno
- Web page: https://patentgrep.com/patent/US12223978B2

## CPC

- G10L 21/0232: Processing in the frequency domain
- H04R 1/403: {loud-speakers}
- H04R 1/26: Spatial arrangements of separate transducers responsive to two or more frequency ranges
- H04R 3/12: for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)}
- H04S 7/302: {Electronic adaptation of stereophonic sound system to listener position or orientation (H04S7/301 takes precedence)}
- G10L 2021/02166: {Microphone arrays; Beamforming}
- H04R 2499/13: Acoustic transducers and sound field adaptation in vehicles
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- 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)
- H04S: STEREOPHONIC SYSTEMS

## Abstract

A voice output from an i-th audio source apparatus is adjusted with a frequency transfer function Wii(f) set in an i-th noise reduction filter and is output from an i-th speaker. In the noise reduction filter, a frequency transfer function Wii(f) is set in which the sound is made smaller at frequencies where the gain of the frequency transfer function Cim(f) from the SPKi to a user tends to be relatively larger than the gain of the frequency transfer function Cii(f) from the SPKi to the user, and the sound is increased at frequencies where the gain of Cim(f) tends to be relatively smaller than the gain of Cii(f), where m is an integer excluding i from 1 to n.

## Claims

### Claim 1

An audio system configured to output sound of different sound sources for each of n users from a 1st user to an n-th user, where is n>2, the audio system comprising:
n sound source devices from the 1st to the n-th;
n speakers from the 1st to the n-th; and
n filters,
wherein the i-th filter, where i is an integer of 1 to n, is configured to transmit a sound output from the i-th sound source device to the i-th speaker with a set frequency transfer characteristic;
wherein the frequency transfer characteristic set for the i-th filter is a frequency transfer function for reducing sound at a frequency at which a gain of a frequency transfer function from the i-th speaker to the m-th user is greater than a gain of a frequency transfer function from the i-th speaker to the i-th user, and increasing sound at a frequency at which of a gain of a frequency transfer function from the i-th speaker to the m-th user is less than a gain of a frequency transfer function from the i-th speaker to the i-th user, where m is an integer excluding i from 1 to n; and
wherein when Cii(f) is a frequency transfer function from the i-th speaker to the i-th user, C*ii(f) is a complex conjugate of Cii(f), Cim(f) is a frequency transfer function from the i-th speaker to the m-th user, and C*im(f) is a complex conjugate of Cim(f), a frequency transfer characteristic Wij set for the i-th filter is expressed by the equation:
W
ii
(
f
)
=
1
1
+
∑
m
=
1
m
≠
i
n
(
C
im
*
(
f
)
⁢
C
im
(
f
)
/
C
ii
*
(
f
)
⁢
C
ii
(
f
)
)
.

### Claim 2 (depends on 1)

The audio system according to claim 1, wherein a frequency transfer characteristic of an adaptive filter is set as a frequency transfer characteristic in an i-th filter, the frequency transfer characteristic being obtained as a result of performing an adaptive operation in which a difference between a sound obtained by applying a frequency transfer function the same as a frequency transfer function from the i-th speaker to an i-th user to a sound output from the i-th sound source device and an output of a microphone arranged at a listening position of a sound of the i-th user, and an output of the microphone arranged at a listening position of a sound of an m-th user are set as errors, in the adaptive filter in which the sound output from the i-th sound source device is an input and an output from the i-th speaker.

### Claim 3 (depends on 1)

The audio system according to claim 1, wherein a frequency transfer characteristic of an adaptive filter is set as a frequency transfer characteristic in an i-th filter, the frequency transfer characteristic being obtained as a result of performing, in the adaptive filter having a sound output from an i-th sound source device as an input and an output as an input of an i-th speaker, an adaptive operation in which a difference between a sound obtained by applying a frequency transfer function the same as a frequency transfer function from the i-th speaker to an i-th user to a sound output from an i-th user, and an output of a microphone arranged at a listening position of the sound of the i-th user is weighted by a predetermined weight and a value obtained by weighting an output of the microphone arranged at the listening position of the sound of the m-th user with a weight set for each microphone as an error.

### Claim 4 (depends on 1)

The audio system according to claim 1, wherein each of the filters is a graphic equalizer.