Improved Cantonese Tone Recognition with Approximated F0 Contour: Implications for Cochlear Implants

This paper describes a periodicity-enhancement strategy which can be used to improve lexical tone perception for cochlear implant (CI) users. We focus on Cantonese, a major Chinese dialect with complex tone system. Acoustical simulations were tested with normal-hearing subjects. Temporal envelope and periodicity components (TEPC) below 500 Hz were extracted from four frequency bands. Stimuli were the combination of TEPC-modulated noises from sub-bands. For enhancement, the original temporal periodicity cues between 20 and 500 Hz were simplified by a sinusoidal wave whose frequency was equal to the exact fundamental frequency (F0) of the original speech or a linearly approximated F0. Tone identification tests were conducted using Cantonese disyllabic words. Results showed that tone scores with periodicity-enhanced TEPCs were significantly higher than the original ones. The approximated F0 contour provides similar tone perception performance to the exact F0 contour, indicating that exact F0 is unnecessary for the periodicity-enhancement strategy in CIs.