Sound quality evaluation of anti-saturation circuitry in a hearing aid.
ABSTRACT 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.
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ABSTRACT: To measure hearing aid performance using circuitry representative of the major eras of technological advancement during the 20th century. Twenty subjects with audiometric profiles consistent with hearing aid candidacy were fit with each of seven hearing aids. No directional microphones were used and binaural benefit was not assessed. Each hearing aid was fit to the strategy or fitting scheme of the era, or that which was intended by the presenting manufacturer. Electroacoustic and/or real ear measures of gain, output, bandwidth, and distortion were obtained. Objective outcome measures assessing speech perception in backgrounds of noise were obtained. Subjective outcome measures of sound quality and ease of listening were obtained in the laboratory and in real life settings. Electroacoustic and real ear measures indicate that gain and bandwidth have increased, and output and distortion have decreased with current electronic aids. Speech perception ability across the different outcome measures showed significantly poorer performance with the body and linear hearing aids when input levels were high; when input levels were low, outcome measures with hearing aids using a dynamic range compression were not negatively affected. At the most adverse signal to noise ratios, none of the hearing aids was shown to be superior. Measured bandwidth did not correlate highly with speech perception ability for any of the objective outcome measures used. For the subjective measures of sound quality done in a blinded manner, no significant differences were found across different listening situations for current hearing aids. The two most important factors for aided speech perception appear to be the audibility and distortion of the signal. No current compression scheme proved superior with the outcome measures used in this investigation.Ear and Hearing 01/2001; 21(6):625-39. · 3.26 Impact Factor