A cross-linguistic validation of locus equations: Are there ‘‘phonetic hot spots’’ in CV acoustic space?

Abstract

A previous study [Sussman etal., J. Acoust. Soc. Am. 90, 1309–1325 (1991)] of American English CV coarticulation showed a remarkably linear relationship between onset frequencies of F2 transitions (plotted along the ordinate) in relation to midvowel target frequencies (plotted along the abscissa) in CVC tokens with initial /bdg/ followed by ten medial vowels. Slope and y intercept of regression functions (‘‘locus equations’’) fitted to these coordinates systematically varied as a function of stop place. Discriminant analyses, using as predictor variables, slope and y intercept, yielded 100% correct classification of stop place categories. Locus equations provide a systematic lawfulness to coarticulatory variation and a relationally invariant phonetic index for stop place classification. The present study extends the metric to three additional languages−Thai, Cairean Arabic, and Urdu. Resulting scatterplots were extremely linear and varied as a function of stop place. Plotting slope Xy intercept yields a derived map of CV phonetic space with which to relationally compare 2, 3, and 4-stop place languages. Within-language stop place contrasts were consistly divergent in CV space. Variability of labial, alveolar/dental, and velar coordinates across five languages showed fairly broad clustering of stop place categories, rather than narrowly focused ‘‘phonetic hot spots.’’ The data are discussed in relation to quantal and adaptive dispersion theories. [Work supported by NSF.]