TOWARD ARTICULATORY-ACOUSTIC MODELS FOR LIQUID APPROXIMANTS BASED ON MRI AND EPG DATA .1. THE LATERALS

Magnetic resonance images of the vocal tract during the sustained phon ation of /l/ (both dark and light allophones) by four native American English talkers are employed for measuring lengths, area functions, an d cavity volumes and for the analysis of 3-D vocal tract and tongue sh apes. Electropalatography contact profiles are used for studying inter - and intra-talker variabilities and as a source of converging evidenc e for the magnetic resonance imaging study. The general 3-D tongue bod y shapes for both allophones of /l/ are characterized by a linguo-alve olar contact together with inward lateral compression and convex cross sections of the posterior tongue body region. The lateral compression along the midsagittal plane enables the creation of flow channels alo ng the sides of the tongue. The bilateral flow channels exhibit somewh at different areas, a characteristic which is talker-dependent. Dark / l/s show smaller pharyngeal areas than the light varieties due to tong ue-root retraction and/or posterior tongue body raising. The acoustic implications of the observed geometries are discussed. (C) 1997 Acoust ical Society of America.