Involvement of the Critical Band in Identification, Perceived Distance, and Discrimination of Vowels

Abstract

Psychoacoustic models of vowel perception typically assume a critical-bandwidth filter, CBF, at the first stage of auditory frequency analysis (e.g., Zwicker et al., 1979; Searle et al., 1979). In spite of the apparent consensus about the validity of the CBF assumption, little perceptual evidence relating CBF to vowel perception is available. The most compelling perceptual evidence appears to be the high correlation observed between perceptual vowel spaces and physical vowel spaces obtained from the output of a bank of 1/3 oct filters (e.g., Pols et al., 1969). This perceptual evidence is not only indirect, but in addition is limited to one aspect of vowel perception: similarity judgments. The present study attempts to examine more directly and in greater detail the contribution of CBF to vowel perception. To obtain more direct evidence, listeners were required to judge changes in vowel formant frequency that were equal in terms of critical bandwidth units. The perceptual consequences of such acoustic changes were examined at the level of identification, ratings of phonetic goodness, and pair-wise discrimination of vowels. The study employed two different back-front place of articulation vowel continua. These continua were presented to normal listeners and to sensorineural hearing impaired listeners.