Abstract
Objectives: Mandarin-speaking users of cochlear implants (CI) perform poorer than their English counterpart. This may be because present CI speech coding schemes are largely based on English. This study aims to evaluate the relative contributions of temporal envelope (E) cues to Mandarin phoneme (including vowel, and consonant) and lexical tone recognition to provide information for speech coding schemes specific to Mandarin.Design: Eleven normal hearing subjects were studied using acoustic temporal E cues that were extracted from 30 continuous frequency bands between 80 and 7,562 Hz using the Hilbert transform and divided into five frequency regions. Percent-correct recognition scores were obtained with acoustic E cues presented in three, four, and five frequency regions and their relative weights calculated using the least-square approach.Results: For stimuli with three, four, and five frequency regions, percent-correct scores for vowel recognition using E cues were 50.43–84.82%, 76.27–95.24%, and 96.58%, respectively; for consonant recognition 35.49–63.77%, 67.75–78.87%, and 87.87%; for lexical tone recognition 60.80–97.15%, 73.16–96.87%, and 96.73%. For frequency region 1 to frequency region 5, the mean weights in vowel recognition were 0.17, 0.31, 0.22, 0.18, and 0.12, respectively; in consonant recognition 0.10, 0.16, 0.18, 0.23, and 0.33; in lexical tone recognition 0.38, 0.18, 0.14, 0.16, and 0.14.Conclusion: Regions that contributed most for vowel recognition was Region 2 (502–1,022 Hz) that contains first formant (F1) information; Region 5 (3,856–7,562 Hz) contributed most to consonant recognition; Region 1 (80–502 Hz) that contains fundamental frequency (F0) information contributed most to lexical tone recognition.
Highlights
Hearing loss is a common sensory disorder and has become an important global health problem due to the increasing prevalence and its negative impact on quality of life
The Tukey’s test revealed that the scores obtained from conditions combined with Frequency Region 5 would be higher than those obtained from conditions combined without Region 5 (Region 123, Region 124, Region 134, and Region 234) (p < 0.05)
The Tukey’s test revealed that the scores obtained from conditions combined with Frequency Region 1 would be higher than those obtained from conditions combined without Region 1 (Region 234, Region 235, Region 245, and Region 345) (p < 0.05)
Summary
Hearing loss is a common sensory disorder and has become an important global health problem due to the increasing prevalence and its negative impact on quality of life. The mainstream CI speech processing strategies, such as advanced combination encoder (Psarros et al, 2002), SPEAK (Skinner et al, 2002), and n-of-m (Ziese et al, 2000; Buechner et al, 2009) are based on the continuous interleaved sampling strategy (Wilson et al, 1991; Boëx et al, 1996). For the continuous interleaved sampling speech processing strategy, the electrode array is successively spaced with a single stimulus, that is, only one electrode is emitting the stimulus current at a time, and the interference and diffusion of the stimulus current between two electrodes are prevented by alternating stimulation (Zeng et al, 2008). Even as the most successful neural implants in the world, there is still much to be studied and improved in signal processing strategies
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