Vocal tract area functions for an adult female speaker based on volumetric imaging

Magnetic resonance imaging (MRI) was used to acquire vocal tract shapes of ten vowels and two liquid approximants for a 27-year-old adult female. These images were complemented with additional images acquired with electron beam computed tomography (CT). Each 3-D shape was condensed into a set of cross-sectional areas of oblique sections perpendicular to the centerline of the vocal tract's long axis, resulting in an 'area function.' Formant frequencies computed for each area function showed reasonable similarity to those determined from the natural (recorded) speech of the imaged subject, but differences suggest that some of the imaged vocal tract shapes were articulated differently during imaging than during recording of natural speech, and also that imaging procedures may have compromised some accuracy for a few shapes. The formant calculations also confirmed the significant effect that the pitiform sinus can have on lowering the formant frequencies. A comparison is made between area functions derived using both MRI and CT methods. Additionally, the area functions reported in this study are compared with those from two previous studies and demonstrate general similarities in shape but also obvious differences that can be attributed to anatomical differences of the imaged subjects and to differences in imaging techniques and image processing methods.