Effects of real-time cochlear implant simulation on speech production.

Investigations using normal-hearing subjects listening to simulations of cochlear implant (CI) acoustic processing have provided substantial information about the impact of these distorted listening conditions on the accuracy of auditory perception, but extensions of this method to the domain of speech production have been limited. In the present study, a portable, real-time vocoder was used to simulate conditions of CI auditory feedback during speech production in NH subjects. Acoustic-phonetic characteristics of sibilant fricatives, aspirated stops, and F1/F2 vowel qualities were analyzed for changes as a result of CI simulation of acoustic speech feedback. Significant changes specific to F1 were observed; speakers reduced their phonological vowel height contrast, typically via talker-specific raising of the low vowels [æ] and [ɑ] or lowering of high vowels [i] and [u]. Comparisons to the results of both localized feedback perturbation procedures and investigations of speech production in deaf adults with CIs are discussed.