Mid-sagittal cut to area function transformations: Direct measurements of mid-sagittal distance and area with MRI

Abstract

This paper presents a comparative study of transformations used to compute the area of cross-sections of the vocal tract from the mid-sagittal measurements of the vocal tract. MRI techniques have been used to obtain both mid-sagittal distances and cross-sections of the vocal tract for French oral vowels uttered by two subjects. The measured cross-sectional areas can thus be compared to the cross-sectional areas computed by the different transformations. The evaluation is performed with a jackknife method where the parameters of the transformation are estimated from all but one measurement of a speaker's vocal tract region and evaluated on the remaining measurement. This procedure allows the study of both the performance of the different forms of transformation as a function of the vocal tract region and the stability of the transformation parameters for a given vocal tract region. Three different forms of transformation are compared: linear, polynomial and power function. The estimation performances are also compared with four existing transformations.