Abstrait

The Growth of Loudness in Cochlear Implant Listeners

Mirza Baig

There are limited psychophysical measurements on growth of loudness in early-deafened cochlear implant users as compared to postlinguallydeafened cochlear implants users. In this study, the “shape” of the loudness growth function was investigated for prelingually- and postlinguallydeafened subjects by measuring loudness growth within the electrical dynamic range on different bipolar electrode pairs using Absolute magnitude Estimation (AME) and Absolute magnitude Production (AMP). The shapes of the loudness functions were obtained and verified by comparing loudness growth models using the Akaike’s Information Criterion (AIC) method to get the best- fit functions. Results suggest that adult cochlear implant listeners can exhibit different loudness growth functions, counting on their acoustical experience before implantation. Eight subjects with considerable acoustic experience before implantation and comparatively late implantation demonstrated loudness functions that grew consistent with an expansive nonlinearity, in agreement with results from several previous studies. In contrast, the four early deafened subjects with little or no useful acoustic experience before implantation, had loudness functions that grew in proportion to stimulus current amplitude. These results suggest that the form of the loudness function is molded partially by the character and functionality of input to the central sensory system during auditory development.