# US 11,122,366 B2 · Method and apparatus for attenuation of audio howling

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- Number: US 11,122,366 B2
- Document ID: US11122366B2
- Status: Granted
- Kind: B2
- Application number: 16/782,744
- Filed: 2020-02-05
- Published: 2021-08-05
- Granted: 2021-09-14
- Earliest claimed: 2020-02-05
- Assignees: Continental Automotive Systems, Inc.
- Applicants: Continental Automotve Systems, Inc.
- Inventors: Mike Reuter
- Web page: https://patentgrep.com/patent/US11122366B2

## CPC

- H04R 3/02: for preventing acoustic reaction {, i.e. acoustic oscillatory feedback (specially adapted for hearing aids H04R25/453)}
- G10L 21/0232: Processing in the frequency domain
- H04R 1/025: {Arrangements for fixing loudspeaker transducers, e.g. in a box, furniture}
- G10L 2021/02082: {the noise being echo, reverberation of the speech}
- G10L 2021/02163: {Only one microphone}
- H04R 2430/03: Synergistic effects of band splitting and sub-band processing
- H04R 2499/13: Acoustic transducers and sound field adaptation in vehicles
- 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)
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

Regions of the audio frequency spectrum that are most susceptible to howling are identified or determined. When detected, these approaches shape the frequency spectrum of the audio going to loudspeakers so that only those howling frequencies are suppressed.

## Claims

### Claim 1

A system for attenuating howling at a speaker, the system comprising:
an audio speaker;
a microphone;
a control circuit coupled to the audio speaker and the microphone, the control circuit configured to:
create an estimate of an echo path signal based upon an input to the audio speaker and an output of the microphone;
dynamically generate an acoustic filter according to selected ones of a plurality of frequencies in the estimate of the echo path signal, wherein each of the selected ones of the plurality of frequencies have respective modeled channel frequency response magnitudes greater than unity and corresponding respective channel mask magnitude values that are correspondingly less than unity;
convert an analog microphone signal received at the microphone to a digital microphone signal;
apply the digital microphone signal to the acoustic filter creating an attenuated digital signal, the attenuated digital signal including an attenuation of the echo path signal by the corresponding respective channel mask magnitude values only at the selected ones of the plurality of frequencies thereby preventing audio howling at the selected ones of the plurality of frequencies;
convert the attenuated digital signal to an attenuated analog signal;
wherein the audio speaker renders the attenuated analog signal to a user.

### Claim 2 (depends on 1)

The system of claim 1, wherein the audio speaker, control circuit, and microphone are disposed in a vehicle.

### Claim 3 (depends on 1)

The system of claim 1, wherein the vehicle is a car, a truck, an aircraft, or a ship.

### Claim 4 (depends on 1)

The system of claim 1, wherein the estimate of the echo path signal is created by subtracting the output of the microphone from the output of the acoustic filter, the subtraction creating a difference.

### Claim 5 (depends on 4)

The system of claim 4, wherein the filter is configured so as to minimize the square of the difference.

### Claim 6 (depends on 1)

The system of claim 1, wherein noise attenuation is also applied to the digital microphone signal.

### Claim 7 (depends on 1)

The system of claim 1, wherein the digital microphone signal is in the frequency domain and the analog microphone signal is in the time domain.

### Claim 8 (depends on 1)

The system of claim 1, wherein the microphone is a hands-free microphone.

### Claim 9

A method for attenuating howling at a speaker, the method comprising:
providing an audio speaker, a microphone, and a control circuit;
by the control circuit:
creating an estimate of an echo path signal based upon an input to the audio speaker and an output of the microphone;
dynamically generating an acoustic filter according to selected ones of a plurality of frequencies in the estimate of the echo path signal, wherein each of the selected ones of the plurality of frequencies have respective modeled channel frequency response magnitudes greater than unity and corresponding respective channel mask magnitude values that are correspondingly less than unity;
converting an analog microphone signal received at the microphone to a digital microphone signal;
applying the digital microphone signal to the acoustic filter creating an attenuated digital signal, the attenuated digital signal including an attenuation of the echo path signal by the corresponding respective channel mask magnitude values only at the selected ones of the plurality of frequencies thereby preventing audio howling at the selected ones of the plurality of frequencies;
converting the attenuated digital signal to an attenuated analog signal;
wherein the audio speaker renders the attenuated analog signal to a user.

### Claim 10 (depends on 9)

The method of claim 9, wherein the audio speaker, control circuit, and microphone are disposed in a vehicle.

### Claim 11 (depends on 9)

The method of claim 9, wherein the vehicle is a car, a truck, an aircraft, or a ship.

### Claim 12 (depends on 9)

The method of claim 9, wherein the estimate of the echo path signal is created by subtracting the output of the microphone from the output of the acoustic filter, the subtraction creating a difference.

### Claim 13 (depends on 12)

The method of claim 12, wherein the filter is configured so as to minimize the square of the difference.

### Claim 14 (depends on 9)

The method of claim 9, wherein noise attenuation is also applied to the digital microphone signal.

### Claim 15 (depends on 9)

The method of claim 9, wherein the digital microphone signal is in the frequency domain and the analog microphone signal is in the time domain.

### Claim 16 (depends on 9)

The method of claim 9, wherein the microphone is a hands-free microphone.

### Claim 17 (depends on 1)

The system of claim 1, wherein the corresponding respective channel mask magnitude values are inversely proportional to the respective modeled channel frequency response magnitudes.

### Claim 18 (depends on 9)

The method of claim 9, wherein the corresponding respective channel mask magnitude values are inversely proportional to the respective modeled channel frequency response magnitudes.