Binaural speech unmasking and localization in noise with bilateral cochlear implants using envelope and fine-timing based strategies.
Four adult bilateral cochlear implant users, with good open-set sentence recognition, were tested with three different sound coding strategies for binaural speech unmasking and their ability to localize 100 and 500 Hz click trains in noise. Two of the strategies tested were envelope-based strategies that are clinically widely used. The third was a research strategy that additionally preserved fine-timing cues at low frequencies. Speech reception thresholds were determined in diotic noise for diotic and interaurally time-delayed speech using direct audio input to a bilateral research processor. Localization in noise was assessed in the free field. Overall results, for both speech and localization tests, were similar with all three strategies. None provided a binaural speech unmasking advantage due to the application of 700 micros interaural time delay to the speech signal, and localization results showed similar response patterns across strategies that were well accounted for by the use of broadband interaural level cues. The data from both experiments combined indicate that, in contrast to normal hearing, timing cues available from natural head-width delays do not offer binaural advantages with present methods of electrical stimulation, even when fine-timing cues are explicitly coded.
van Hoesel
Richard
R
Cooperative Research Centre for Cochlear Implant and Hearing Aid Innovation, Melbourne, Vic 3002 Australia. rvanh@bionicear.org
Böhm
Melanie
M
Pesch
Jörg
J
Vandali
Andrew
A
Battmer
Rolf D
RD
Lenarz
Thomas
T
D001309:Auditory Threshold; D003054:Cochlear Implants; D006801:Humans; D009622:Noise; D010470:Perceptual Masking; D013017:Sound Localization; D013067:Speech Perception; D013997:Time Factors