VOCAL-TRACT AREA FUNCTIONS FROM MAGNETIC-RESONANCE-IMAGING

There have been considerable research efforts in the area of vocal tra ct modeling but there is still a small body of information regarding d irect 3-D measurements of the vocal tract shape. The purpose of this s tudy was to acquire, using magnetic resonance imaging (MRI), an invent ory of speaker-specific, three-dimensional, vocal tract air space shap es that correspond to a particular set of vowels and consonants. A set of 18 shapes was obtained for one male subject who vocalized while be ing scanned for 12 vowels, 3 nasals, and 3 plosives. The 3-D shapes we re analyzed to find the cross-sectional areas evaluated within planes always chosen to be perpendicular to the centerline extending from the glottis to the mouth to produce an ''area function.'' This paper prov ides a speaker-specific catalogue of area functions for 18 vocal tract shapes. Comparisons of formant locations extracted from the natural ( recorded) speech of the imaged subject and from simulations using the newly acquired area functions show reasonable similarity but suggest t hat the imaged vocal tract shapes may be somewhat centralized. Additio nally, comparisons of the area functions reported in this study are co mpared with those from four previous studies and demonstrate general s imilarities in shape but also obvious differences that can be attribut ed to differences in imaging techniques, image processing methods, and anatomical differences of the imaged subjects. (C) 1996 Acoustical So ciety of America.