Recruitment in Noise-Induced Hearing Loss

Abstract

A group of subjects with sensory-neural noise-induced hearing loss was tested with a fixed-frequency Békésy type audiometer. Responses were studied for signs of abnormal auditory adaptation and increased differential sensitivity. Adaptation was defined as a poorer threshold response to a continuous tone than to an interrupted tone. Increased differential sensitivity was defined as a narrower envelope of responses to the continuous tone than to the interrupted tone. It was found that all subjects showed both of these effects to some degree. It is suggested that adaptation increases differential sensitivity by raising the threshold. It would seem impossible to measure a sensitivity differential unaffected by adaptation in this category of hearing loss. It is concluded that a fixed-frequency Békésy technique may be the most fruitful approach to recruitment testing since both effects may be measured concurrently with this procedure.