Principal component analysis of cross sections of tongue shapes in vowel production
Images of the vocal tract provide the speech researcher with new and unique data. However, quantification of the "biologically important" features present in the image is a significant challenge because these features are typically complex, inherently variable and difficult to describe. The present study quantified cross sectional tongue shape for vowels in a single plane (post-alveolar) using Principal Component Analysis. A single subject repeated eleven English vowels in two consonant contexts, five times each. Each of the resulting cross-sectional waveshapes (tokens) was represented by 70 samples. The 110 tokens were placed in a 110 x 70 matrix for PCA. The resulting principal components represent a basis set of orthonormal waveshapes with properties particularly suitable for the present project. The first two components accounted for 93% of the variance in the data. The loadings of the eleven vowels on the first two PCs indicated three distinct shape groups. These were examined statistically and found to represent high vowels, front Vowels and back vowels. (C) 1997 Elsevier Science B.V.
principal component analysis tongue shapes vowels ultrasound