Sophia Symposium on New Technology and the Investigation of the Articulatory Process, pp. 33-49, Sophia University, 2004
Comparing tongue position of vowels in oral and nasal contexts
Abstract: We studied the formant frequency shifts of a nasalized vowel from the aspects of acoustics and production. For the acoustic aspect, formant frequencies were measured in the following three cases: 1) vowels produced by physical models of a vocal tract, 2) nasal and oral vowels intentionally uttered by a human speaker, 3) nasalized vowels uttered in a nasal context. As predicted by the acoustic theory and the perceptual findings, bidirectional formant shifts in F1 frequency were observed by acoustic analyses: increasing F1 for high vowels and decreasing F1 for low vowels. Then, we tried to answer to the next question, that is, whether or not speakers and/or listeners compensate for the formant shifts in production and/or in perception. The perceptual experiment by Arai [J. Acoust. Soc. Am., 115, p.2541 (2004)] showed that compensation occurs when an isolated vowel has nasalization and is accompanied by formant transitions. This result agrees with the findings of Krakow et al. [J. Acoust. Soc. Am. 83, 1146-1158 (1988)] which reported that the formant shifts due to nasalization do not necessarily lead to the misperception of a vowel in a word with nasal context. In the production experiment, the measurement of the positions of the articulators showed almost no compensation except for the lowest vowel /a/.