Vowel Intelligibility in Chinese

Conventional wisdom states that, since the average amplitude of vowel articulation significantly exceeds that for consonants, an assessment of spoken intelligibility in obscuring noise should primarily be limited by consonant confusion. Furthermore, in both English and Chinese, consonant discrimination is considered to be more important to overall intelligibility than that of vowels. In the unbounded case, the assumption that vowel confusion is less important than consonant confusion may well be true; however, at least two situations exist where the influence of vowel confusion may be greater. The first is where vocabulary-specific restrictions confine the structure of a particular spoken word to alternatives differing primarily in their vowel. The second is the prevalence of non-additive white Gaussian noise (AWGN) interference, particularly impulsive noise which obscures only the vowel portion of a word, and similarly is present as a nonlinear effect of many time-sliced processing algorithms. This paper explores the issue of vowel intelligibility for spoken Chinese, where the confusion characteristics are complicated through the influence of lexical tone carried by the vowel in consonant-vowel-consonant (CVC) structure utterances. Experimental evidence from multilistener intelligibility testing are presented to build toward an understanding of the characteristics of Mandarin Chinese vowel confusion in the presence of AWGN. Results are also isolated by carrier word consonants and in terms of the lexical tone overlaid upon tested vowels. In particular, several factors relating to issues such as vowel length, tone combination and the crucial influence of the /a/ (IPA([a])) phone are revealed.