AN INVESTIGATION OF STOP PLACE OF ARTICULATION AS A FUNCTION OF SYLLABLE POSITION - A LOCUS EQUATION PERSPECTIVE

Locus equations were employed to phonetically describe stop place cate gories as a function of syllable-initial, -medial, and -final position . Ten speakers, five male and five female, produced a total of 2700 CV C and 4500 VCV utterances that were acoustically analyzed to obtain F2 onset, F2 vowel, and F2 offset frequencies for locus equation regress ion analyses. In general, degree of coarticulation, as indexed by locu s equation slope, was reduced for post-vocalic (VC) stops relative to pre-vocalic stops (pooled data from initial and medial positions), but significant differences were observed as a function of stop consonant . All stops showed significantly reduced R-2 values and increased stan dard errors of estimate for VC relative to CV productions. Separabilit y of stop place categories in a higher-order slope X y-intercept acous tic space also diminished for VC vs CV stop productions. The degradati on of classic locus equation form (high correlation and linearity) for VC relative to CV productions was attributed to greater articulatory precision in the production of pre-vocalic compared to post-vocalic st ops. This greater articulatory precision was interpreted as reflecting a greater need to normalize vowel context-induced variability of the F2 transition for syllable onset relative to final stops. The decline in acoustic lawfulness of syllable-final stops is discussed in terms o f coarticulatory interactions and expected perceptual correlates. (C) 1997 Acoustical Society of America.