Estimation of vocal tract shapes from speech sounds with a physiological articulatory model

Abstract

A 3D physiological articulatory model based on volumetric MRI data from a male speaker was used to estimate vocal tract shapes from speech sounds. The advantages of using the model for the inverse estimation are that the model is equipped with the morphological and dynamic constraints that are commonly used for such estimation and possesses the physiological constraints that are involved in human articulation. In this study, a dynamic muscle workspace was introduced to account for temporal variations of the muscle orientation with articulatory movements, and a multipoint control strategy was proposed for flexible control of the tongue tip and tongue dorsum. The control points were used as articulatory parameters, and formants were chosen as acoustic parameters. An articulatory constraint between the F1−F2 difference and tongue dorsum position was introduced in mapping formant patterns to control point positions, where the constraint was obtained based on X-ray microbeam data recorded from the target speaker and five other male speakers. The proposed estimation method was evaluated using vowel-to-vowel sequences. For the target speaker of the model, the average estimation error was 0.16 cm for the vocal tract shapes, and 1.8% for the four lower formants. This implies that our physiological articulatory model can be a valuable tool for the inverse estimation.