On delay-based technique for acoustic feedback cancellation in digital hearing aids

This paper proposes an efficient method for continuous adaptive feedback cancellation (AFC) in digital hearing aids. The AFC is achieved by two filters: an adaptive filter to model and track variations in the acoustic feedback path, and a piecewise-fixed filter for feedback neutralization. The proposed method employs a delay-based technique where an appropriate delay is inserted in the signal flow path and an extended-length filter is used for the AFC. An efficient strategy is proposed to check when the AFC filter reaches the optimal solution. Furthermore, the proposed strategy can detect when there is a strong perturbation in the acoustic path, and hence AFC filter is reinitialized. The computer simulations are carried out to demonstrate the effectiveness of the proposed method. We observe that, as compared with the conventional method, the proposed method gives robust performance even in the case of a strong perturbation in the acoustic path.