# US 7,609,841 B2 · Frequency shifter for use in adaptive feedback cancellers for hearing aids

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 7,609,841 B2
- Document ID: US7609841B2
- Status: Granted
- Kind: B2
- Application number: 10/912,690
- Filed: 2004-08-04
- Published: 2005-12-08
- Granted: 2009-10-27
- Earliest claimed: 2003-08-04
- Assignees: House Ear Institute
- Inventors: Daniel J. Freed; Sigfrid D. Soli
- Web page: https://patentgrep.com/patent/US7609841B2

## CPC

- H04R 25/453: {electronically}
- H04R 5/023: {in a chair, pillow}
- 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

A decorrelation method for improving feedback cancellation utilizes a small frequency shifting ratio, on the order of 0.3 percent. Frequency shifting is applied only to the high frequency portion of the signal, which is shifted alternately upward and downward.

## Claims

### Claim 1

A decorrelation method for improving feedback cancellation comprising:
sampling an input signal;
separating the input signal into a low frequency component and a high frequency component;
shifting the high frequency component by an amount corresponding to a frequency shift of less than six percent, wherein the high frequency component is shifted alternately upward and downward in frequency;
computing an output signal corresponding to the sampled input signal as the sum of the low frequency component and shifted high frequency component.

### Claim 2 (depends on 1)

The method of claim 1 wherein the high frequency component is shifted by an amount corresponding to a frequency shift of less than one percent.

### Claim 3 (depends on 1)

The method of claim 1 wherein the high frequency component is shifted by an amount corresponding to a frequency shift of approximately 0.3 percent.

### Claim 4 (depends on 1)

The method of claim 1 wherein the shift direction of the high frequency component is alternated at regular intervals.

### Claim 5

A decorrelation method for improving feedback cancellation comprising:
sampling an input signal;
shifting at least one component of a predetermined number of samples of the input signal by an amount corresponding to a frequency shift in a first direction of less than six percent;
shifting said at least one component of a next predetermined number of samples of the input signal by an amount corresponding to a frequency shift in a second direction, opposite to the first direction, of less than six percent;
continuing to alternately shift said predetermined numbers of samples of the input signal;
computing an output signal corresponding to the sampled input signal as the sum of the at least one shifted component and unshifted components, if any.

### Claim 6 (depends on 5)

The method of claim 5 wherein the at least one component is shifted by an amount corresponding to a frequency shift of less than one percent.

### Claim 7 (depends on 5)

The method of claim 5 wherein the at least one component is shifted by an amount corresponding to a frequency shift of approximately 0.3 percent.

### Claim 8 (depends on 5)

The method of claim 5 wherein the input signal is separated into a low frequency component and a high frequency component and wherein only the high frequency component is shifted.