Method for control of adaptation of feedback suppression in a hearing aid, and a hearing aid

1. A method of controlling adaptation of a feedback suppression filter in a hearing aid, comprising the steps of:

converting an input sound into a microphone output signal;

deriving an input signal from the microphone output signal;

subtracting a feedback suppression signal from the input signal hereby providing a hearing aid processor input signal;

adapting filter coefficients of a feedback suppression filter using the hearing aid processor input signal as control signal;

forming a hearing aid processor output signal by applying an amplification gain to the hearing aid processor input signal;

filtering the hearing aid processor output signal in the feedback suppression filter to derive the feedback suppression signal; and

suspending the adaptation of the feedback suppression filter when the level of a hearing aid reference signal is below a predetermined threshold, thereby indicating there is insufficient sound signal available for adaptation of said feedback suppression filter.

2. The method according to claim 1 , wherein the input signal is selected as the hearing aid reference signal.

3. The method according to claim 1 , wherein the hearing aid processor output signal is selected as the hearing aid reference signal.

4. The method according to claim 1 , wherein a whitened hearing aid processor output signal is selected as the hearing aid reference signal.

5. A method of controlling adaptation of a feedback suppression filter in a hearing aid, comprising the steps of:

converting, in a first microphone, input sound into a first microphone output signal, and converting, in a second microphone, input sound into a second microphone output signal;

adding the first microphone output signal and the second microphone output signal hereby forming a first spatial signal;

subtracting the first microphone output signal from the second microphone output signal hereby forming a second spatial signal;

subtracting a first feedback suppression signal from the first spatial signal, hereby providing a first processor input signal;

subtracting a second feedback suppression signal from the second spatial signal, hereby providing a second processor input signal;

adapting filter coefficients of a first feedback suppression filter using as control signal the first processor input signal;

adapting filter coefficients of a second feedback suppression filter using as control signal the second processor input signal;

processing of the first processor input signal and the second processor input signal to form a hearing aid processor output signal;

filtering the hearing aid processor output signal in the first feedback suppression filter to derive the first feedback suppression signal;

filtering the hearing aid processor output signal in the second feedback suppression filter to derive the second feedback suppression signal;

suspending the adaptation of the first feedback suppression filter when the level of a first hearing aid reference signal is below a first predetermined threshold, thereby indicating there is insufficient sound signal available for adaptation of said first feedback suppression filter; and

suspending the adaptation of the second feedback suppression filter when the level of a second hearing aid reference signal is below a second predetermined threshold, thereby indicating there is insufficient sound signal available for adaptation of said second feedback suppression filter.

6. The method according to claim 5 , wherein the first spatial signal is selected as the first hearing aid reference signal and the second spatial signal is selected as the second hearing aid reference signal.

7. A hearing aid comprising:

a microphone for converting sound into a microphone output signal;

an adaptive feedback suppression filter for adaptively estimating a feedback path and for generating a feedback suppression signal;

means for combining the feedback suppression signal with the microphone output signal to form a processor input signal;

hearing aid processing means for processing the processor input signal to form a hearing aid processor output signal;

an output transducer for converting the hearing aid processor output signal into an acoustic output;

means for detecting the level of a hearing aid reference signal and comparing the level of the hearing aid reference signal with a predetermined threshold level indicating there is sufficient sound signal available for adaptation; and

means for suspending adaptation of the adaptive feedback suppression filter when the hearing aid reference signal level is below the predetermined threshold level.

8. A hearing aid comprising:

a first microphone for converting sound into a first microphone output signal;

a second microphone for converting sound into a second microphone output signal;

first spatial transformation means for adding the first microphone output signal and the second microphone output signal hereby forming a first spatial signal;

second spatial transformation means for subtracting the first microphone output signal from the second microphone output signal hereby forming a second spatial signal;

means for combining a first feedback suppression signal with the first spatial signal hereby providing a first processor input signal;

means for combining a second feedback suppression signal with the second spatial signal hereby providing a second processor input signal;

means for processing of the first processor input signal and the second processor input signal to form a hearing aid processor output signal;

an output transducer for converting the hearing aid processor output signal into an acoustic output;

a first adaptive feedback suppression filter for adaptively deriving the first feedback suppression signal by filtering the hearing aid processor output signal, using as control signal the first processor input signal;

a second adaptive feedback suppression filter for adaptively deriving the second feedback suppression signal by filtering the hearing aid processor output signal, using as control signal the second processor input signal;

means for suspending adaptation of the first feedback suppression filter when the level of a first hearing aid reference signal is below a first predetermined threshold, thereby indicating there is insufficient sound signal available for adaptation of said first feedback suppression filter; and

means for suspending adaptation of the second feedback suppression filter when the level of a second hearing aid reference signal is below a second predetermined threshold, thereby indicating there is insufficient sound signal available for adaptation of said second feedback suppression filter.