Development and achievement of hearing-aid fitting strategy based on loudness model

Abstract

The purpose of this study was to develop a hearing‐aid fitting strategy (named NYMU strategy), which aimed to compensate the loudness perception of hearing‐impaired individuals as that of normal‐hearing individuals. The loudness growth curve of normal‐hearing individuals was derived by the equal loudness contour. The loudness growth curve of hearing‐impaired individuals was constructed by fitting the curve through three points, which were the uncomfortable loudness level, the most comfortable loudness level, and the pure‐tone threshold of hearing‐impaired individuals for each frequency band. The NYMU strategy primarily calculated the hearing‐aid gain for each frequency band according to the differences between the loudness growth curve of normal‐hearing individuals and that of hearing‐impaired individuals; the gain was set to guarantee the audibility of the lowest boundary of speech intensity with normal vocal effort. Furthermore, the NYMU strategy adopted an innovative approach, which adjusted the point of the most comfortable loudness level to fine‐tuning the loudness growth curve, and it resulted in the fine‐tuning gain of each band. The preliminary results reveal that the NYMU strategy provides more gain above 4,000 Hz and under 500 Hz, compared with the NAL‐NL1 strategy. In addition, three of five subjects get higher word recognition scores when they were fitted by the NYUM strategy rather than the NAL‐NL1 strategy.