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Abstract:
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.
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