Tone modifications used for improving the discrimination of Mandarin words for the hearing-impaired

In this paper, a digital processing method is described for modifying tone contrast that was defined as the difference in frequencies between peaks and valleys of pitch curves in natural utterances. Speech signals with modified tones were presented to hearing-impaired Chinese listeners who were asked to identify four alternative Mandarin words. Employing this method, it was found that modified speech with enhanced tone contrast contributed moderate gains in the percentage correct word identification when compared to unmodified speech, while reducing tone contrast generally reduced the percentage correct identification. These findings therefore offer support to the assertion that a hearing aid with tone modifications is indeed effective for hearing-impaired Chinese.