A Novel Zerocrossing Based Electrical Stimulation Strategy for Cochlear Implant Incorporating Frequency-Specific Fine Structure Cue

摘要

This paper introduces a novel electrical stimulation strategy for cochlear implant (CI). For low frequency (LF) channels, the zerocrossing time is used to represent the fine structure cue of speech signal and evoke an electrical pulse. For high frequency (HF) channels, the pulses are produced sequentially when no zerocrossing appears at LF channels. The fact that only one pulse is elicited at one moment diminishes the possibility of crosstalk of electrical pulses from adjacent channels. Acoustic simulation experiment was conducted to investigate the performance of the proposed strategy for Mandarin phase identification. 10 Mandarin-speaking subjects participated in the experiment, and each subject listened to 20 sounds synthesized by traditional continuous-interleaved-sampling (CIS) algorithm and the proposed algorithm in their 6-channel versions, respectively. The experimental results showed that the proposed algorithm produced higher correct rate for Mandarin phase identification than the CIS algorithm, even when the Mandarin voices were contaminated by the speech-spectrum shaped noise at low signal-to-noise-ratio levels. It is believed that the proposed electrical stimulation strategy would facilitate our development of novel CI products to further improve the speech perception of CI users, particularly those speaking tonal languages.