Understanding the effect of noise on electrical stimulation sequences in cochlear implants and its impact on speech intelligibility.

Understanding the effect of noise on electrical stimulation sequences in cochlear implants and its impact on speech intelligibility. Hear Res. 2013 Feb 7; Authors: Qazi OU, van Dijk B, Moonen M, Wouters J Abstract The present study investigates the most important factors that limit the intelligibility of the cochlear implant (CI) processed speech in noisy environments. The electrical stimulation sequences provided in CIs are affected by the noise in the following three manners. First of all, the natural gaps in the speech are filled, which distorts the low-frequency ON/OFF modulations of the speech signal. Secondly, speech envelopes are distorted to include modulations of both speech and noise. Lastly, the N-of-M type of speech coding strategies may select the noise dominated channels instead of the dominant speech channels at low signal-to-noise ratio's (SNRs). Different stimulation sequences are tested with CI subjects to study how these three noise effects individually limit the intelligibility of the CI processed speech. Tests are also conducted with normal hearing (NH) subjects using vocoded speech to identify any significant differences in the noise reduction requirements and speech distortion limitations between the two subject groups. Results indicate that compared to NH subjects CI subjects can tolerate significantly lower levels of steady state speech shaped noise in the speech gaps but at the same time can tolerate comparable levels...
Source: Hearing Research - Category: Audiology Authors: Tags: Hear Res Source Type: research