A reconsideration of locus equations as invariants for place of articulation of stop consonants

Abstract

It has been claimed that locus equations, representing linear relationships between F2 at vowel midpoint and onset for CV syllables, predict place of articulation for stop consonants [H. M. Sussman etal., J. Acoust. Soc. Am. 90, 1309–1325 (1991)]. However, the slopes of these regression lines are shown to be flexible. Insofar as the slopes reflect the influence of vowels on preceding consonants, they can be changed by manipulating the degree of coarticulation. In this study, speakers produced /b/, /d/, and /g/ followed by various vowels at fast, normal, and slow rates of speech. In the fast productions the consonant was preceded by the same vowel that followed it, and in the slow productions it was preceded by the vowel schwa, which placed competing demands on the articulators to reduce anticipatory coarticulation by the following vowel. The fast productions resulted in higher slopes for each consonant, while the slow productions resulted in lower slopes. Subjects in a perceptual study were presented with tokens of /b/, /d/, and /g/ with identical slopes and asked to identify the consonants. Results indicate that identification of consonants is not predicted by the slopes of their regression lines. [Work supported by NICHD Grant No. HD-01994.]