Speech Perception under Spectral Shift and Compression-Expansion Conditions: A Cochlear Implant Simulation Study

Abstract

The effects of spectral shift and spectral distortions (individual and combined) on speech recognition were measured using acoustic simulations.The present study included 30 participants with normal-hearing (NH), listening to acoustic cochlear implant (CI) simulations to measure speech recognition under spectrally matched, shifted, compression and expansion conditions for Kannada Quick Sin sentences, generated by 16-channel, noise-band vocoder. In the shift-only condition, the frequency ranges of the carrier bands were shifted up or down relative to the analysis bands. In the compression- and expansion-only conditions, the analysis band- range was made larger or smaller, compared to the carrier band range. Measurements were made in noise (with four talker babble at 0 dB SNR). A statistically significant difference was present for both, compression and expansion conditions when compared to the perfect frequency and place matched condition. Scores were significantly poorer in the expansion compared to compression condition. Information from the present study will help in understanding the effect of spectral manipulations on speech recognition ability in noise.