Phonetic acoustic invariance and the antimetrical vocal tract shape
Kozo Ohta, Kazuhiro Fuchi · The Journal of the Acoustical Society of America · 1984
The antimetrical vocal tract shape (VTS) means the vocal tract cross-sectional area function which is estimated directly from speech waves by the PARCOR algorithm assumed that the vocal tract characteristic becomes antimetrical on utterance of vowels [K. Fuchi, Tech. Group Acoust. Soc. Jpn. Pap. S77-05 (1977)]. As the result of a detailed experiment it is shown that the essence of the phonetic quality of vowel-like sounds is fully described by the antimetrical VTS [K. Ohta and K. Fuchi, J. Acoust. Soc. Jpn. 39 (3), 173–184 (1983)]. An attempt to find a phonetic acoustic invariance is reported based on the antimetrical VTS. Articulatory quantities close to the invariance are presented in both static and dynamic cases. For the former it is demonstrated that articulatory quantities independent to interspeaker variation (between males and females, among males or among females) can be extracted by reducing a neutral VTS from shapes of five vowels for each speaker. For the latter a difference of the sound which arises in the glide of vowels is investigated. A semivowel is perceived when the vocal tract characteristic holds antimetrical during the glide, but any speech sound is not perceived when the characteristic does not hold.