Examing Listeners' Ability to Perceive Vowel-Inherent Spectral Changes

Abstract

One family of theories regarding vowel perception suggests onset and offset formant-frequencies are important for identification and that the shape of the transitions themselves are not otherwise perceptually important. The present study determined just-noticeable-differences in deviations from 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, and fundamental frequency. Data from the first experiment indicate that listeners are largely insensitive to deviations from linearity of formant trajectory but that large enough deviations could eventually be detected. The size of these deviations seems dependent on the range of onset-offset formant frequencies. However, a second experiment in which only the first half of stimuli was presented thereby affecting the frequency range of the stimuli, gave different results. Results from these experiments along with several hypotheses are presented.