A Comparison between Conventional and Wavelet Based Amplitude Compression Schemes

Loudness recruitment is a symptom of sensorineural hearing loss affecting the inner ear when the threshold of hearing is raised. The increase of the hearing threshold is often nonuniform across the range of audible frequencies and loudness perceptions are distorted. One method used to compensate for this type of hearing disorder is amplitude compression followed by equalization. In the present study, we compared amplitude compression in the discrete domain via two methods: 1) conventional two-channel amplitude compression, as proposed by Villchur and 2) wavelet based compression scheme using three levels of decompositionlreconstruction with the DB-9 wavelet. Both of these algorithms were tested on normal hearing subjects with elevated thresholds simulated by masking noise. The subjects were tested using nonsense sentences and the merit of each scheme was determined from the percentage of correctly identified keywords relative to linear amplification.