Common modes of vocal tract articulation for vowels

Abstract

The purpose of this study was to investigate the spatial similarity of vocal tract shaping patterns across speakers and the similarity of their acoustic effects. Vocal tract area functions for eleven American English vowels were first obtained from six speakers, three female and three male, using magnetic resonance imaging (MRI). Each speaker’s set of area functions was then decomposed into mean area vectors and representative modes (eigenvectors) using principal components analysis (PCA). Three modes accounted for more than 90% of the variance in the original data sets for each speaker. The general shapes of the first two modes were found to be highly correlated across all six speakers. To demonstrate the acoustic effects the modes, both isolated and combined, a mapping between the mode scaling coefficients and [F1,F2] pairs was generated for each speaker. The mappings were unique for all six speakers in terms of the exact shape of the [F1,F2] vowel space, but the general effect of the modes was the same in each case. The results tend to support the idea that the modes provide a common system for perturbing a unique underlying neutral vocal tract shape. [Work supported by NIH R01-DC04789.]