Effects of Preferred and Prescribed Gain on Speech Perception in Noise - A Validation of Prescriptive Formulae

Abstract

This study aimed at investigating the effects of prescribed gain and preferred gain on speech perception in noise. Two widely used prescriptive formulae (NAL-N LI & DSL- IIO) were employed in this study. Two groups of hearing impaired individuals with gradually sloping and steeply sloping loss served as subjects. REIG and SNR threshold measurements were carried out in each subject. The results showed that REIG measured at preferred and prescribed gain in NAL-N LI as well as DSL-I/O were significantly different in most of the frequencies for both the groups. However, the amount and direction of difference was frequency dependent. In some frequencies the difference between preferred and prescribed gain was not significant. In SNR threshold estimation there were no significant differences between preferred and prescribed gains. The only exception was the gradually sloping hearing loss group, which revealed significant differences for both NAL-NLI and DSL-i/o at 65 dB SPL.