Shrikanth Narayanan
Abeer Alwan
Dept. of Elec. Eng., 66-147E Eng. IV, UCLA, 405 Hilgard Ave., Los Angeles, CA 90024
Kate Haker
Cedars-Sinai Med. Ctr., Los Angeles, CA 90048
In this study, 3-D tongue shapes reconstructed from MR images obtained during sustained production of the fricatives /s,(sh),z,(yog)/ by four speakers are analyzed. Images were collected in the coronal, axial, and sagittal planes using a GE SIGNA 1.5 T machine with image slice thickness of 3 mm and no interscan spacing. Results show that the tongue body for /s/ and /z/ is significantly lowered behind the constriction with respect to the tip and back of the tongue; the tongue body has flat or slightly convex contours in the constriction region that become significantly concave behind the constriction. The degree of concavity is speaker dependent, and decreasing concavity is observed as the posterior pharyngeal wall is approached. For /(sh)/ and /(yog)/, the tongue body rises slightly along its midline before it starts sloping towards its posterior end; the tongue shape behind the constriction is convex (two subjects) or flat (two subjects) and gradually turns concave towards the posterior region. The ``grooving'' effect in /s,z/ contributes to a relatively abrupt increase in the area function behind the constriction when compared to /(sh),(yog)/. Similarly, raising of the tongue back in /s,z/ results in smaller areas near the velum when compared to /(sh),(yog)/. The acoustic significance of these articulatory shapes are discussed. [Work supported in part by NSF.]