A Method For Determining Periodically Time-Varying Bias And Its Applications In Acoustic Feedback Cancellation

Adaptive filters have been widely used for feedback cancellation in audio systems including hearing aids. In addition to adaptive filters, the frequency shifting has often been used to obtain an unbiased estimation of the adaptive filters, by decorrelating the incoming and outgoing signals of the audio system. However, it has been shown in a recent study, that although the frequency shifting technique is effective in decorrelating the signals, its use in addition to the adaptive filter would introduce an additional and signal dependent periodically time-varying bias also referred to as the residual bias, especially for tonal signals such as music. In this work, we make use of that knowledge and propose a method to detect different acoustic situations, based on the level of residual bias. We further discuss on some control actions to be taken in acoustic feedback cancellation systems upon these detections. Finally, we demonstrate the behavior of the residual bias and the detection of different acoustic feedback situations in an example computer simulation.