Principal Component Analysis of Ultrasound Images of Tongue Contours during Speech

Abstract

The shape and movement of the tongue are critical in the formation of human speech. Modern imaging techniques allow scientists to study tongue shape and movement without interfering with speech. This presentation describes statistical issues arising from ultrasound imaging of tongue contour data. There are many sources of variability in tongue image data, including speaker- to-speaker differences, intraspeaker differences, noise in the images, and other measurement problems. To make matters worse, the tongue is supported entirely by soft tissue, so no fixed co-ordinate system is available. Statistical methods to deal with these problems are presented. The goal of the research is to associate tongue shapes and sound production. Principal component analysis is used to reduce contours. Combinations of two basic shapes accurately represent tongue contours. The results are physiologically meaningful and correspond well to actual speech activity. The methods are applied to a sample of 16 subjects, each producing four vowel sounds.