A method to combine acoustic and morphological constraints in the speech production inverse problem

Abstract

This paper approaches the articulatory-to-acoustic speech production inverse case. A framework based on an explicit combination of vocal-tract morphological and acoustic constraints is proposed. The solution is based on a Fourier analysis of the vocal-tract log-area function: the relationship between the log-area Fourier cosine coefficients and the corresponding formants is used to formulate an acoustic constraint. The same set of coefficients is then used to express a morphological constraint. This representation of both acoustic and morphological constraints in the same parameter space allows an efficient solution for the inverse problem. The basis of the acoustic constraint formulation was first proposed by Mermelstein (1967). However, at that time, the combination with morphological constraints was not realized. The method is tested for some vowels. The results confirm the validity of the method, but they also show the need for dynamic constraints.