A novel method of improving sound quality and reducing acoustic feedback in hearing aids

Most current hearing aids have relatively narrow bandwidths, when compared to high-fidelity equipment, and exhibit undamped peaks because the peaks are considered less troublesome than the problem of wax-clogged dampers. Attempting to make hearing aids wider band has typically resulted in increased acoustic feedback problems. The recent availability of an off-the-shelf digital hearing aid integrated circuit amplifier, which contains several biquad filters, when used with special software, automatically detects and suppresses peaks. The filters then further flatten and extend the hearing aid frequency response to 16 kHz, while the appropriate CORFIG correction is added to the frequency response, producing a transparent sound. Open ear versus aided KEMAR recordings were produced using a live jazz trio and a string quartet. The sound quality ratings for eight commercially available digital hearing aids were obtained from several different listening panels. The new response equalization proved advantageous in all cases. The effects of eliminating the peaks in the response on maximum real ear gain achievable before onset of acoustic feedback oscillation will be reported.