Computer simulation of the fitting of hearing aids based on prediction of the discrimination ability of speech sounds

Abstract

The earlier version of the computer program for simulating the process of fitting hearing aids [S. Hiki and Y. Fukuda, “Prediction of the ability of discrimination of speech sounds by hearing impaired children,” J. Acoust. Soc. Am. Suppl. 1 68, S5 (1980)] has been modified so that correction for individual speaker differences can be made. The latest version of the program consists of two parts. In the first part, by inputting various characteristics of the hearing loss of an impaired child and the candidate hearing aid, parameters of the hearing aid are controlled. The goal of the adjustment is to match the sound pressure versus frequency range, audible for each impaired child with the aided characteristics, to that of typical speech sounds. In the second part, the type of identifiable phones and probable phonetic confusions among the phones are estimated by analyzing the relationship between the aided characteristics and the acoustical properties of the speech sounds. The corrections for individual speaker characteristics involve the average amount of shift of formant frequencies for all vowels due to the differences of shape of the vocal tract, the deviation of average value of the fundamental frequency, and the deviation of intensity of the unvoiced sounds relative to the vowels.