A parametric area function model of three female vocal tracts based on orthogonal modes
Brad H. Story · The Journal of the Acoustical Society of America · 2002
Image sets corresponding to 11 vowels were obtained from each of 3 female speakers using Magnetic Resonance Imaging. From these images, vocal tract area functions for each vowel were determined. Each speaker’s 11 area functions were then decomposed into a set of orthogonal basis functions or ‘‘modes’’ and mean vowel area functions. Similar to previous work with male vocal tract data [Story and Titze, J. Phon. (1998)], two orthogonal modes accounted for nearly 90% of the variance within each speaker’s vowel set, while the mean area functions serve as neutral, but unique, tract shapes around which the vowels are formed. For each speaker, the two most significant modes and the mean area function were used to develop a parametric model that allowed for calculation of an arbitrary area function based on coefficients of the modes. With these models a hypothetical vowel space was generated in terms of F1, F2 pairs (first and second formant frequencies). The vowel spaces for each speaker were then used to map time-varying formant frequencies extracted from natural speech to the modal coefficients of their respective parametric models. This effectively produces a time-varying area function suitable for synthesis of speech. [Work supported by NIH R01-DC04789.]