On the use of a phase modulation method for decorrelation in acoustic feedback cancellation

A major problem in using an adaptive filter in acoustic feedback cancellation systems is that the loudspeaker signal is correlated with the signals entering the microphones of the audio system, leading to biased filter estimates. One possible solution for reducing this problem is by means of decorrelation. In this work, we study a subband phase modulation method, which was originally proposed for decorrelation in multichannel acoustic echo cancellation systems. We determine if this method is effective for decorrelation in acoustic feedback cancellation systems by comparing it to a structurally similar frequency shifting decorrelation method. We show that the phase modulation method is suitable for decor-relation in a hearing aid acoustic feedback cancellation system, although the frequency shifting method is in general slightly more effective.