Inverse estimation of the vocal tract shape based on a vocal tract mapping interface

This paper describes the inverse estimation of the vocal tract shape for vowels by using a vocal tract mapping interface. In prior research, an interface capable of generating a vocal tract shape by clicking on its window was developed. The vocal tract shapes for five vowels are located at the vertices of a pentagonal chart and a different shape that corresponds to an arbitrary mouse-pointer position on the interface window is calculated by interpolation. In this study, an attempt was made to apply the interface to the inverse estimation of vocal tract shapes based on formant frequencies. A target formant frequency data set was searched based on the geometry of the interface window by using a coarse to fine algorithm. It was revealed that the estimated vocal tract shapes obtained from the mapping interface were close to those from magnetic resonance imaging data in another study and to lip area data captured using video recordings. The results of experiments to evaluate the estimated vocal tract shapes showed that each subject demonstrated unique trajectories on the interface window corresponding to the estimated vocal tract shapes. These results suggest the usefulness of inverse estimation using the interface.