Studying articulatory variability using functional data analysis

Abstract

This paper examines articulatory variability across repetitions using functional data analysis. In this analysis, signals are time-normalized using a smooth function of time. The magnitude of the time-warping function provides an index of phasing (temporal) variability; a separate index of amplitude variability is calculated from the time-normalized signal. Here, lip, jaw, and tongue movements in vowel–consonant–vowel sequences recorded using a magnetometer were used for the analysis. Preliminary results suggest articulator specific patterns of variability. Thus vertical jaw movements showed small amplitude variability for alveolar consonants, like /s, t/. As expected, the amplitude variability of the tongue tip was small during alveolar consonants, where the tip is in contact with the alveolar ridge. However, the amplitude of the tongue tip movement varied considerably at the release of alveolar stops. The horizontal and vertical movements of the same articulator often showed a different amount of amplitude variability. For example, during the movement from the first to the second vowel in /api/, the tongue body showed small vertical and large horizontal variability. The results will be discussed in terms of articulatory, acoustic, and perceptual constraints on speech production. [Work supported by CNPq, Brazil, and NIH.]