Determination of vocal-tract shapes from formant frequencies based on perturbation theory and interpolation method

Abstract

Band-limited Fourier expansion, containing both odd and even components, has proven to be useful for representing human vocal-tract (VT) area function in the inverse problem of speech production. The Fourier coefficients can be estimated from the pole/zero frequencies of the VT transfer function. However, the difficulties encounted in determining the VT length and extracting zero frequencies from speech signal make this approach almost impossible to implement. This paper proposes an interpolation method that allows zero frequencies and the VT length to be derived accurately, and from which the VT area function can be determined subsequently based on perturbation theory. A root-cell code book is used to facilitate dynamic vowel-to-vowel (VV) transition. A computationally efficient implementation of the dynamic process for VV transition is presented. Simulation results are given.