Sound quality evaluation of anti-saturation circuitry in a hearing aid

Loud sounds amplified by conventional hearing aids produce saturation distortion. This paper presents a comparison between a Class D hearing aid that was allowed to amplify into saturation and a Class D hearing aid that contained circuitry to prevent saturation distortion. The study was performed to determine whether users judged the conventional hearing aid or the anti-saturation hearing aid to have better sound quality. Seventeen subjects with hearing losses performed sound quality judgments at two sites. At low input levels, where the measured distortion was low, the subjects rated both hearing aids equal in sound quality. At high input levels, the subjects preferred the anti-saturation hearing aid, which had significantly lower distortion than the standard hearing aid. Though these data do not correlate the measured distortion to the subjective sound quality, the relationship revealed between the two in this testing warrants further investigation.