Measurement and adaptive suppression of acoustic feedback in hearing aids

The authors describe a technique for making in situ measurements of the acoustic feedback path transfer function and present results demonstrating the effect of changes in the acoustic environment on this transfer function. Three methods of feedback suppression are explored: time-varying delay, adaptive inverse filtering, and adaptive feedback cancellation. It is concluded that the latter approach is the most successful, increasing the maximum gain the hearing aid can deliver without acoustic feedback by 6-10 dB. This increased gain can provide a benefit for moderately-impaired listeners