A Method of Managing Adaptive Feedback Cancellation in Hearing Devices and Hearing Devices Configured to Carry out Such Method

A method of managing adaptive feedback cancellation in a hearing device comprising:

• estimating an external acoustic feedback path transfer function by modeling a first estimated feedback path transfer function to reflect the external acoustic feedback path transfer function;
• modifying an input signal of the hearing device, based on the first estimated feedback path transfer function, thereby generating a compensated input signal;
• generating a probe signal;
• injecting the probe signal into an output signal of the hearing device and providing the probe signal to the microphone through an external acoustic feedback path;
• deriving at least a reference estimated feedback path transfer function based on a relation between the input signal and the probe signal;
• comparing the at least reference estimated feedback path transfer function with the first estimated feedback path transfer function;
• and
• controlling an adaptive filter unit and a frequency shift unit based on a comparison between the at least a reference estimated feedback path transfer function and the first estimated feedback path transfer function.

The method of claim 22, wherein the step of controlling the adaptive filter unit and the frequency shift unit comprises the steps of:

• if the measured value of the difference is below a given adaptation threshold value, freezing an adaptation of the feedback canceller unit by deactivating the adaptive filter unit;
• deactivating the frequency shift unit;
• and
• only if the measured value of the difference is equal or above the given adaptation threshold value, allowing adaptation of the feedback canceller unit by activating the adaptive filter unit and activating the frequency shift unit.

A hearing device comprising:

• a microphone;
• a receiver;
• signal processing circuitry configured to receive from the microphone an input signal and to provide the receiver with an output signal,
• wherein an external acoustic feedback path defined by feedback sound traveling from the receiver to the microphone is represented by an external feedback path transfer function;
• and
• wherein the signal processing unit comprises:
• a gain unit;
• a feedback canceller unit comprising an adaptive filter unit configured to derive a first estimated feedback path transfer function reflecting the external acoustic feedback path transfer function and configured to adaptively accommodate changes in the external acoustic feedback path transfer function;
• a frequency shift unit configured to stabilize an adaptation of the feedback canceler unit;
• signal compensation means for compensating the input signal of the hearing device, based on the first estimated feedback path transfer function, thereby generating a compensated input signal,
• wherein the signal processing unit further comprises an adaptation control block comprising:
• signal generating means for generating a probe signal;
• signal injection means for injecting the probe signal into the output signal of the hearing device and for letting the probe signal be fed back to the microphone through the external acoustic feedback path;
• calculating means for modeling at least a reference estimated feedback path transfer function, based on a relation between the input signal and the probe signal;
• and
• a comparison unit configured to compare the at least a reference estimated feedback path transfer function with the first estimated feedback path transfer function and to control the adaptive filter unit and the frequency shift unit based on a comparison there between.