Acoustic feedback cancellation in hearing aids

The authors describe a maximum phase cancellation scheme for hearing aids that prevents acoustic oscillations. In this scheme, the open-loop phase delay in the primary audio frequency region is cancelled to the largest extent possible. At the same time, the magnitude response of the new open-loop transfer function outside the primary audio frequency region is suppressed by using negative feedback. The use of both these techniques increases the stability and the maximum usable gain of the overall hearing aid system. Computer simulations, using real measured data, were used to confirm the results.<>