Use of acoustic analysis to develop, test and optimize cochlear implant sound processing

Over the last 30 years, numerous psychophysical tests have been conducted in cochlear implant listeners, Most of the previous research, however, has been conducted with a single electrode bypassing the subjects' clinical sound processors. While useful for evaluating the limits of auditory capability with electrical stimulation, without subjects' sound processors, it is not possible to analyze contributions of changes in signal processing to clinical outcome. The principal goal of this dissertation is to use acoustic analyses to develop, test, and optimize cochlear implant sound processing. If acoustic measures can evaluate the perception of detailed clinically-relevant electric stimulation features, it will provide insight into the advantages and disadvantages of different sound processing strategies, and have important implications for developing and improving processing strategies. This dissertation used three different acoustic analyses including spectral-ripple discrimination, Schroeder-phase discrimination, and temporal modulation detection to evaluate the sensitivity of cochlear implant users to specific acoustic elements relevant to clinical success. The relationship between the psychophysical performance and speech and music perception performance were examined. Using the acoustic measures, this dissertation evaluated commercially available cochlear implant sound processing strategies, and furthermore, suggested a new sound processing strategy overcoming identified weaknesses of the strategies. In addition, a potential application of the psychophysical measures to investigate auditory evoked potentials is also presented.