ADAPTIVE FEEDBACK CANCELLATION WITH FREQUENCY COMPRESSION FOR HEARING-AIDS

The use of an adaptive feedback canceler (AFC) for howling suppression in hearing aids seems very attractive since it is not only unaffected by the changes in the operating environment, but it also limits signa l degradation due to the feedback signal. This, however, requires a re ference signal which is correlated with the feedback signal but not wi th the input signal. In hearing aids, such a signal is hard to obtain. The output signal could be used as reference if its correlation with the input signal could sufficiently be removed. If the reference signa l is correlated with the input signal, the input signal will also be c anceled by the AFC. Here, the use of a frequency compressor as a decor relator is proposed. The performance of this system is then investigat ed via digital simulation. Results indicated that with the use of the proposed system and the proper choice of system parameters, an increas e of about 18 dB in the howling margin could be achieved with minimal deterioration in output signal quality.