Neural Tracking of Band-Limited Sine-Wave Speech in Normal Hearing and Cochlear Implant Listeners

Abstract

A sine-wave speech represents complex speech with a limited number of sinusoidal components. Functionally, its strategy draws a close similarity to the signal processing strategy in cochlear implant (CI) which transmits speech envelope information in limited number of channels. In this study, we investigated how synchronous cortical activities to speech envelope relates to the speech intelligibility of sine-wave speech in different bandwidths with both normal hearing (NH) and CI listeners. 12 NH and four CI participants were recruited. We divided our NH participants into two groups: 1) Six NH listeners, 2) six NH listening to CI simulation synthesized using a noise vocoder. In our third group, 3) four CI users, one of them participated in only behavioral tests. Neural tracking was obtained using multi-channel electroencephalogram (EEG) system and cross-checked with behavioural performance, speech perception scores and speech quality ratings. Our result showed that intelligible sine-wave speech can be built with a small number of sinusoidal components selected from the original speech spectrum. Our cross-correlation analysis between cortical activities and speech envelope fluctuation showed an increasing trend in their synchrony with sine-wave speech built using more sinusoidal components for both group 2) and 3). Cortical entrainment to speech envelope is more observable in CI users compared to NH listened to CI simulated sine-wave speech. Our result have implications for understanding of neural tracking in terms of spectrally degraded speech perception in NH and CI individuals. Keywords: Sinusoidal model, electroencephalogram (EEG), cortical entrainment, speech intelligibility, hearing prosthesis. Read more →