Simulations of cochlear implant hearing using filtered harmonic complexes: implications for concurrent sound segregation.
Two experiments used simulations of cochlear implant hearing to investigate the use of temporal codes in speech segregation. Sentences were filtered into six bands, and their envelopes used to modulate filtered alternating-phase harmonic complexes with rates of 80 or 140 pps. Experiment 1 showed that identification of single sentences was better for the higher rate. In experiment 2, maskers (time-reversed concatenated sentences) were scaled by -9 dB relative to a target sentence, which was added with an offset of 1.2 s. When the target and masker were each processed on all six channels, and then summed, processing the masker on a different rate to the target improved performance only when the target rate was 140 pps. When the target sentence was processed on the odd-numbered channels and the masker on the even-numbered channels, or vice versa, performance was worse overall, but showed similar effects of pulse rate. The results, combined with recent psychophysical evidence, suggest that differences in pulse rate are unlikely to prove useful for concurrent sound segregation.
Deeks
John M
JM
MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 2EF, United Kingdom.
Carlyon
Robert P
RP
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold; D003054:Cochlear Implants; D005260:Female; D006801:Humans; D008297:Male; D010470:Perceptual Masking; D010897:Pitch Discrimination; D012815:Signal Processing, Computer-Assisted; D013067:Speech Perception / Q000502:physiology*