Enhancing Chinese tone recognition by manipulating amplitude envelope: Implications for cochlear implants

Abstract

Tone recognition is important for speech understanding in tonal languages such as Mandarin Chinese. Cochlear implant patients are able to perceive some tonal information by using temporal cues such as periodicity-related amplitude fluctuations and similarities between the fundamental frequency (F0) contour and the amplitude envelope. The present study investigates whether modifying the amplitude envelope to better resemble the F0 contour can further improve tone recognition in multichannel cochlear implants. Chinese tone and vowel recognition were measured for six native Chinese normal-hearing subjects listening to a simulation of a four-channel cochlear implant speech processor with and without amplitude envelope enhancement. Two algorithms were proposed to modify the amplitude envelope to more closely resemble the F0 contour. In the first algorithm, the amplitude envelope as well as the modulation depth of periodicity fluctuations was adjusted for each spectral channel. In the second algorithm, the overall amplitude envelope was adjusted before multichannel speech processing, thus reducing any local distortions to the speech spectral envelope. The results showed that both algorithms significantly improved Chinese tone recognition. By adjusting the overall amplitude envelope to match the F0 contour before multichannel processing, vowel recognition was better preserved and less speech-processing computation was required. The results suggest that modifying the amplitude envelope to more closely resemble the F0 contour may be a useful approach toward improving Chinese-speaking cochlear implant patients' tone recognition.

Spectral and temporal cues for speech recognition: Implications for auditory prostheses

“…Xu et al (2002) also found that, as in English phoneme recognition, there was a tradeoff between the temporal and spectral cues for lexical tone recognition. Efforts aimed at enhancing the temporal envelope cues for tone recognition or pitch perception using acoustic simulations or actual cochlear implants have yielded only modest success (e.g., Geurts and Wouters, 2001;Green et al, 2004Green et al, , 2005Hamilton et al, 2007;Laneau et al, 2006;Luo and Fu, 2004;Vandali et al, 2005Vandali et al, , 2007. On the other hand, few studies have attempted to manipulate the spectral cues to improve tone recognition or pitch perception (e.g., Geurts and Wouters, 2004).…”

Cochlear implants: A remarkable past and a brilliant future

“…Thus, less-thanresolute representations of F0s is a problem for implants, and this problem has received considerable attention (e.g., Wouters, 2001, 2004;Luo and Fu, 2004;Green et al, 2005;Laneau et al, 2006;Carroll and Zeng, 2007;Chatterjee and Peng, 2007;Sucher and McDermott, 2007). Unfortunately, a way to improve the representations has not been identified to date despite these efforts.…”

Contour identification with pitch and loudness cues using cochlear implants

“…Different semitone spacing and intensity changes between successive notes were used to vary the perceptual salience of pitch and loudness cues, respectively, as the integration of both cues may depend on their relative salience. Previously, we have found that CI users' Mandarin tone recognition was enhanced when the amplitude envelope was modified to follow the pitch contour of lexical tone (Luo and Fu, 2004). In this study, CI users' contour identification is hypothesized to be better when pitch and loudness cues are consistent.…”