8-CHANNEL DIGITAL-FILTER BANK FOR HEARING-AID USE - PRELIMINARY-RESULTS IN MONAURAL, DIOTIC AND DICHOTIC MODES

A digital 8-channel signal processing system has been implemented usin g a TMS 320C25 signal processor. Tests with hearing-impaired subjects showed that the system allows a better fit to a specified frequency re sponse than when using conventional aids with analog filtering. The fi lter bank has also been tested in dichotic listening experiments, wher e odd-number channels were fed to one ear and even-number channels to the other. The preliminary results on three hearing-impaired subjects in repeated tests of speech recognition in noise showed an improvement in the order of 2 dB in speech-to-noise ratio for 50% correct recogni tion as compared to the complete broadband signal presented diotically . Temporal splitting of the signal by periodically switching of the od d and even bands between left and right ears did not show any improvem ent.