Feedback cancellation divergence prevention

A hearing assistance device feedback cancellation system, the system comprising:

• an input transducer to transduce an acoustic signal into a transduced signal, the transduced signal including an input signal and a feedback signal;
• a memory;
• a processor configured to execute instructions to:
• determine a plurality of initial feedback filter coefficients based on the input signal and the feedback signal;
• generate a feedback cancellation signal based on the initial feedback filter coefficients, the feedback cancellation signal configured to be combined with the input signal and the feedback signal to cancel the feedback signal;
• detect a reduced input sound level within the input signal subsequent to the generation of the feedback cancellation signal, the reduced input sound level indicating an ambient sound level is substantially equal to or below a noise threshold, the noise threshold determined based on estimated noise floor values;
• determine a plurality of preceding filter coefficients in response to the detection of the reduced input sound level, the plurality of preceding filter coefficients corresponding to a preceding state of filter coefficients immediately prior to the detection of the reduced input sound level;
• determine a plurality of adapted feedback filter coefficients in response to the detection of the reduced input sound level, the plurality of adapted filter coefficients determined based on adapting the plurality of adapted feedback filter coefficients from the plurality of preceding filter coefficients toward a plurality of initialized feedback filter coefficient values, the plurality of adapted feedback filter coefficients to reduce acoustic leakage feedback, the plurality of initialized feedback filter coefficient values determined based on an initial fitting of the hearing assistance device;
• generate an adapted feedback cancellation signal based on the plurality of adapted feedback filter coefficients;
• and
• generate an adapted feedback cancelled output based on a combination of the adapted feedback cancellation signal and the input signal;
• and
• an output transducer to transduce the adapted feedback cancelled output.

At least one non-transitory machine-readable storage medium, comprising a plurality of instructions that, responsive to being executed with processor circuitry of a computer-controlled device, cause the computer-controlled device to:

• receive an input signal and a feedback signal at a hearing assistance device;
• determine a plurality of initial feedback filter coefficients based on the input signal and the feedback signal;
• generate a feedback cancellation signal based on the initial feedback filter coefficients, the feedback cancellation signal configured to be combined with the input signal and the feedback signal to cancel the feedback signal;
• detect a reduced input sound level within the input signal subsequent to the generation of the feedback cancellation signal, the reduced input sound level indicating an ambient sound level is substantially equal to or below a noise threshold, the noise threshold determined based on estimated noise floor values;
• determine a plurality of preceding filter coefficients in response to the detection of the reduced input sound level, the plurality of preceding filter coefficients corresponding to a preceding state of filter coefficients immediately prior to the detection of the reduced input sound level;
• determine a plurality of adapted feedback filter coefficients in response to the detection of the reduced input sound level, the plurality of adapted filter coefficients determined based on adapting the plurality of adapted feedback filter coefficients from the plurality of preceding filter coefficients toward a plurality of initialized feedback filter coefficient values, the plurality of adapted feedback filter coefficients to reduce acoustic leakage feedback, the plurality of initialized feedback filter coefficient values determined based on an initial fitting of the hearing assistance device;
• and
• generate an adapted feedback cancellation signal based on the plurality of adapted feedback filter coefficients.