Zero-crossing based compression hearing aid

Abstract

The motivation of this thesis research was to develop an experimental compression hearing aid that would allow fast attackhelease compression without excessive waveform distortions such as those produced by conventional envelope-based (EVB) compression hearing aids. A zero-crossing-based (ZXB) processing scheme for fast attackhelease compression was proposed. The efficacy of a single-channel and two multichannel ZXB compression hearing aids was evaluated by comparing the speech perceptual performances of these three hearing aids with those of a single-channel linear hearing aid and a conventional single-channel fast attackhelease EVB compression hearing aid. The NST consonant test was administered on two hearing impaired subjects. The results showed that the speech perceptual performances of the ZXB hearing aids were better than those of the linear and EVB compression hearing aids. Analysis of the confusion matrices in terms of articulatory features showed that the superior performance of the ZXB hearing aids can be attributed to the successfulamplification of low intensity consonants by the ZXB compression process which reduces substantially the waveform distortions introduced by the conventional EVB process.