SIGNAL PROCESSING STRATEGIES FOR COCHLEAR PROSTHESIS

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The long term objective of the proposed research is to improve the speech performance of current signal processing strategies for cochlear prosthesis. The present study will propose a series of strategies which will stimulate the electrodes using information that is "closest", perceptually, to the input signal. In these strategies, the channel amplitudes are selected such that the difference between the stimulating (electrical) pattern and the acoustic pattern is minimized, that is, channel amplitudes are selected by optimizing a perceptually motivated error criterion. Two types of error criteria will be investigated, a temporal criterion, which emphasizes the importance of envelope information, and a spectral criterion which emphasizes the importance of spectral information. The proposed experiments have three specific aims. The first aim is to investigate whether a strategy designed for better spectral matching performs better on speech recognition tasks than the conventional Continuous Interleaved Sampling (CIS) strategy. The second aim is to understand the importance of spectral information on word recognition with the Med-El and Nucleus cochlear implant devices. To accomplish this aim, we will present to implant patients sentences from the TIMIT speech corpus in which the vowels or the consonants will be replaced with white noise. The third aim is to investigate whether a strategy designed for better waveform matching performs better on speech recognition tasks than the CIS strategy. The proposed strategies will be implemented on a portable speech processor and will be tested with cochlear implant patients. The results of these investigations will lay the groundwork for a better understanding of which information, temporal (envelope) or spectral, is perceptually more important for cochlear implants. Most importantly, it will open new avenues for the development of future signal processing strategies for cochlear prosthesis.