Perception of vowel-inherent spectral change

Abstract

One family of theories regarding vowel perception suggests that onset and offset formant-frequencies are important for identification but that the shape of the transitions themselves is not perceptually important [e.g., Morrison and Nearey, J. Acoust. Soc. Am. 122, EL15–EL22 (2007)]. The present study determined just-noticeable-differences in deviations for linear formant trajectories. Diphthong-like stimuli were manipulated by inserting a point of inflection into the otherwise linear transition. Several parameters were manipulated including vowel duration, location of the inflection point in time, direction of formant change, and fundamental frequency. Data from the first experiment indicate that listeners are largely insensitive to deviations from linearity of formant trajectory but that deviations that fell outside the range of frequencies spanned by the onset and offset were detectable. However, a second experiment in which only the first half of stimuli were presented gave different results. Results from these experiments along with several hypotheses are presented. [Work supported by SSHRC.]