Pulse-spreading harmonic complex as an alternative carrier for vocoder simulations of cochlear implants.

Noise- and sine-carrier vocoders are often used to acoustically simulate the information transmitted by a cochlear implant (CI). However, sine-waves fail to mimic the broad spread of excitation produced by a CI and noise-bands contain intrinsic modulations that are absent in CIs. The present study proposes pulse-spreading harmonic complexes (PSHCs) as an alternative acoustic carrier in vocoders. Sentence-in-noise recognition was measured in 12 normal-hearing subjects for noise-, sine-, and PSHC-vocoders. Consistent with the amount of intrinsic modulations present in each vocoder condition, the average speech reception threshold obtained with the PSHC-vocoder was higher than with sine-vocoding but lower than with noise-vocoding.