Inductive coupling of hearing aids and telephone receivers

The present investigation sought to determine the effects of hearing loss, signal level, telephone receiver type, and telecoil location on the aided word-discrimination abilities of hearing impaired subjects using electromagnetic coupling of their hearing aids to the telephone. As expected, significant deterioration in discrimination scores was observed with increasing hearing loss. In addition, significant improvement in discrimination scores was observed, for all subject groups, as the signal level increased from 80 dB SPL to 105 dB SPL. Of the four receiver conditions, the U1 and BARC receivers resulted in the best discrimination scores. Also, the results suggest that the U1 and BARC receivers are indeed equivalent in terms of word discrimination scores. Finally, the telecoil location in individual hearing aids appeared to have little influence on the speech discrimination capabilities of the subjects in this study. However caution must be used in interpreting that result, since subjects were allowed to adjust the telephone handset position to maximize the signal level in any given condition. This occasionally resulted in inappropriate handset locations for conventional telephone use.