Abstract
In this study, the theory and procedures of the 60 dB fitting method, a method of hearing aid fitting for profoundly hearing-impaired children, were examined and its validity is discussed in terms of (1) actual hearing and (2) actual speech of profoundly impaired children. The following findings were obtained. 1. Even if the hearing threshold when using small size earphones was at 80 dB SPL, the dynamic range of hearing was about 20 dB and could be as narrow as 10 dB. The dynamic range of hearing was markedly narrow when the hearing threshold was severe and the frequency was high. 2. The subjects' threshold for wearing hearing aids was around 60 dB SPL. 3. Even severely impaired children improved their scores in word intelligibillity tests and consonant intelligibillty tests, probably due to the effects of early education and advances of in hearing aid quality. It was also found that, if the threshold for wearing hearing aid was at 60 dBSPL, word intelligibillty scores were verey good. This could validate the 60 dB fitting method as a method of hearing aid fitting. 4. Speech intelligibillity test scores were greatly improved. This might imply progress in the auditory education in the practical use of hearing aids by using the fitting method that we had been using.
