MRI AND X-RAY EVIDENCE FOR COMMONALITY IN THE DORSAL ARTICULATIONS OF ENGLISH VOWELS AND LIQUIDS

One advantage to using articulatory gestures in models of speech production is that a single gesture can function as a component in a number of different traditional segments. Thus, for example, some models consider the tongue tip constrictions for /t/, /d/, /n / and /l / to be a single gesture, resulting in a much more efficient cognitive model than one based on segmental units. Few claims of this (or any) kind, however, have been made with reference to more dorsal tongue gestures such as those in American /r / and /l/, largely because of the limited means of measuring speech farther back in the mouth. The present paper reports findings supporting a proposed connection between the pharyngeal component of /r / and a hypothesized pharyngeal constriction in schwa, and between the dorsal component of /l / and the low, back vowel 'open o'. First, to verify the existence of a pharyngeal component in American English schwa, early X-ray films produced at Haskins labs were found to show an active pharyngeal retraction in postvocalic schwas produced by all of the three speakers measured. Second, midsagittal MRIs of the vocal tracts of three speakers of American English were collected and midsagittal distance (of airspace above the tongue surface) was measured at 3-mm intervals along the length of the vocal tract, giving an approximation of the vocal tract airspace. Regions of the vocal tract were defined as pharyngeal, uvular and oral, with the pharyngeal region divided into upper and lower halves. These midsagittal distances were measured for eleven sustained vowels plus /r / and /l/. Average distances were calculated for each vowel, and these were subtracted point by point from /r / and /l/, allowing a single rms difference to be calculated within each region of the vocal tract. Results indicate as predicted that in the pharyngeal and upper pharyngeal/uvular regions, /l / showed the greatest correspondence with open o, while /r / was most similar to schwa. 1