# US 10,375,487 B2 · Method and device for filtering signals to match preferred speech levels

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- Number: US 10,375,487 B2
- Document ID: US10375487B2
- Status: Granted
- Kind: B2
- Application number: 15/239,088
- Filed: 2016-08-17
- Published: 2018-02-22
- Granted: 2019-08-06
- Earliest claimed: 2016-08-17
- Assignees: Starkey Laboratories, Inc.
- Applicants: Starkey Laboratories, Inc.
- Inventors: William S. Woods; Tarun Pruthi
- Web page: https://patentgrep.com/patent/US10375487B2

## CPC

- H04R 25/43: {Electronic input selection or mixing based on input signal analysis, e.g. mixing or selection between microphone and telecoil or between microphones with different directivity characteristics (H04R25/407 takes precedence)}
- H04R 1/1083: {Reduction of ambient noise (active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06)}
- H04R 25/55: {using an external connection, either wireless or wired}
- H04R 2225/43: Signal processing in hearing aids to enhance the speech intelligibility
- 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

Described herein are methods and devices for mixing input signals from multiple audio input sources in a hearing device such as a hearing aid. In one embodiment, a gain is applied to a telecoil signal where the gain is computed so as to depend on the level of a microphone signal. The technique does not depend on the user's audiogram and allows control of the gain for all environments with one adjustment.

## Claims

### Claim 1

A hearing device, comprising:
a first audio source component to produce a first input signal;
a second audio source component to produce a second input signal;
processing circuitry to process a combination of the first input signal and the second input signal into an output signal;
a speaker to convert the output signal into an audio output; and,
wherein the processing circuitry is further to:
measure levels of the first and second input signals;
derive a signal-to-noise ratio (SNR) as a ratio between the measured levels of the first and second input signals, respectively, the first input signal being regarded as signal (S) and the second input signal being regarded as noise (N);
calculate a target value SNRpreferred for the SNR, either explicitly or by using a look-up table, as a function of the measured level of the second input signal; and,
apply a gain G to the first input signal in a manner that attempts to maintain the SNR at the target value SNRpreferred where:
G=SNRpreferred−S+N
and where S is the measured level of the first input signal regarded as signal and N is the measured level of the second input signal regarded as noise.

### Claim 2 (depends on 1)

The device of claim 1 wherein the processing circuitry is further to calculate the target value SNRpreferred as a linear function of the measured level of the second input signal.

### Claim 3 (depends on 1)

The device of claim 1 wherein SNRpreferred is calculated as:
SNRpreferred=m*N+b
where the slope m and intercept b are adjustable values.

### Claim 4 (depends on 1)

The device of claim 1 wherein the processing circuitry is further to calculate the target value SNRpreferred as a second order polynomial function of the measured level of the second input signal.

### Claim 5 (depends on 1)

The device of claim 1 wherein the processing circuitry is further to calculate the target value SNRpreferred as a function of the measured level of the second input signal that decreases as the measured level of the second input signal increases.

### Claim 6 (depends on 1)

The device of claim 1 wherein:
the first audio source component is a telecoil to convert a time-varying electromagnetic field sensed by the telecoil into the first input signal; and,
wherein the second audio source component is a microphone to convert sensed sound into the second input signal.

### Claim 7 (depends on 1)

The device of claim 1 wherein:
the first audio source component is a direct audio input (DAI) device to receive signals from an external source; and,
the second audio source component is a microphone to convert sensed sound into the second input signal.

### Claim 8 (depends on 1)

The device of claim 1 wherein:
the first audio source component is a wireless receiver to receive wireless streaming signals and generate the second input signal therefrom; and,
the second audio source component is a microphone to convert sensed sound into the second input signal.

### Claim 9 (depends on 1)

The device of claim 1 wherein the first and second audio source components are both microphones to convert sound into the first and second input signals, respectively.

### Claim 10

A method for operating a hearing device, comprising:
producing a first input signal from a first audio source component;
producing a second input signal from a second audio source component;
measuring levels of the first and second input signals;
deriving a signal-to-noise ratio (SNR) as a ratio between the measured levels of the first and second input signals, respectively, the first input signal being regarded as signal (S) and the second input signal being regarded as noise (N);
calculating a target value SNRpreferred for the SNR, either explicitly or by using a look-up table, as a function of the measured level of the second input signal; and,
applying a gain G to the first input signal in a manner that attempts to maintain the SNR at the target value SNRpreferred; apply a gain G to the first input signal in a manner that attempts to maintain the SNR at the target value SNRpreferred where:
G=SNRpreferred−S+N
and where S is the measured level of the first input signal regarded as signal and N is the measured level of the second input signal regarded as noise;
processing a combination of the first input signal and the second input signal into an output signal; and,
converting the output signal into an audio output.

### Claim 11 (depends on 10)

The method of claim 10 further comprising calculating the target value SNRpreferred as a linear function of the second input signal regarded as noise.

### Claim 12 (depends on 10)

The method of claim 10 further comprising calculating SNRpreferred as:
SNRpreferred=m*N+b
where the slope m and intercept b are adjustable values.

### Claim 13 (depends on 10)

The method of claim 10 further comprising calculating the target value SNRpreferred as a second order polynomial function of the second input signal.

### Claim 14 (depends on 10)

The method of claim 10 further comprising calculating the target value SNRpreferred as a function of the measured level of the second input signal that decreases as the measured level of the second input signal increases.

### Claim 15 (depends on 10)

The method of claim 10 wherein:
the first audio source component is a telecoil to convert a time-varying electromagnetic field sensed by the telecoil into the first input signal; and,
wherein the second audio source component is a microphone to convert sensed sound into the second input signal.

### Claim 16 (depends on 10)

The method of claim 10 wherein:
the first audio source component is a direct audio input (DAI) device to receive signals from an external source; and,
the second audio source component is a microphone to convert sensed sound into the second input signal.

### Claim 17 (depends on 10)

The method of claim 10 wherein:
the first audio source component is a wireless receiver to receive wireless streaming signals and generate the second input signal therefrom; and,
the second audio source component is a microphone to convert sensed sound into the second input signal.

### Claim 18 (depends on 10)

The method of claim 10 wherein the first and second audio source components are both microphones to convert sound into the first and second input signals, respectively.