Simulated phase-locking stimulation: an improved speech processing strategy for cochlear implants.

The continuous interleaved sampling (CIS) speech-processing strategy has been widely used for cochlear implants to extract speech envelope information without preserving phase information. In this study, a novel simulated phase-locking stimulation (SPLS) strategy, which detects zero-crossing times of the narrow-band signal of each band, was developed to extract both phase and amplitude-envelope information from a bank of frequency bands of speech sounds. The advantage of the SPLS strategy over the CIS strategy was confirmed by the results of our psychophysical experiments, showing that normal-hearing Chinese listeners' performance in recognizing SPLS-processed Chinese speech was significantly better than their performance of recognizing CIS-processed Chinese speech under quiet, noise-masking, or speech-masking conditions. Thus, the results suggest that if the SPLS strategy is used to modulate the interval of electrical stimulation pulses in cochlear-implant devices according to extracted phase information, the speech-processing functions of cochlear implant devices would be improved for Chinese cochlear implant users.