Abstract:

Articulatory changes in /s/ over time give rise to the onset and offset of turbulence noise, but the small tolerances involved make it difficult to separately consider the effects of movement, phonetic context, and subject variation. Aerodynamic estimates of the constriction area have been shown to demonstrate a marked asymmetry, with the /s/ onset more rapid than offset [C. Scully, Speech Commun. 11, 1992]. Previous articulatory studies led us to expect an invariant tongue tip position, with jaw raising dependent somewhat on the following vowel. In order to investigate the timing of the constriction formation in fricatives, X-ray microbeam data [Westbury et al., 1994] for citation forms of /sVd/ for 15 vowels were studied. In fact, the tongue marker patterns during [s] vary both by following vowel and subject; subjects seem to have different apical-laminal strategies. The jaw reaches maximum height during [s] for each subject studied; that height does not appreciably vary with vowel. This indicates that jaw height is important specifically for /s/ production. One possibility is that the constriction is formed by the tongue, and turbulence noise is then maximized by the lower teeth being brought into position. [Work supported by NIH NIDCD R01 DC 006705.]