A comparison of x-ray microbeam and ultrasound measurements of the tongue surface during speech

Abstract

Tracking points on the tongue surface provides unique information about its movement, such as surface expansion/contraction, differences in rate of movement along the tongue's surface, and X-Y tongue position. Scanned images of the tongue surface provide different but equally unique information, such as posterior and anterior tongue relationships, tongue shape, tongue rotation, and asymmetry. The present study used two quite different techniques (x-ray microbeam and ultrasound) in a comparative study of tongue movement. A single subject repeated /VCVC/ combinations of /s/, /l/, /i/, /a/, and /o/. The phonemic effects of the consonants on tongue shape were examined, as were the allophonic effects of the three vowels. Tongue minus jaw movements (ultrasound) were compared to tongue plus jaw movements (XRMB). The data indicated that tongue rotation, which was quite common, occurred about a fulcrum whose locus was shifted or obscured by jaw movement. Other results indicated that there was considerable expansion/contraction of the tongue surface during speech. In addition, the surface of the tongue moved at nonuniform rates that were both physiologically and phonemically based.