J. O. Ramsay, K. G. Munhall, V. L. Gracco, D. J. Ostry
Functional Data Analyses of Lip Motion
Abstract:The vocal tract's motion during speech is a complex patterning of the movement of many different articulators according to many different time functions. Understanding this myriad of gestures is important to a number of different disciplines including automatic speech recognition, speech and language pathologies, speech motor control and experimental phonetics. Central issues are the accurate description of the shape of the vocal tract and determining how each articulator contributes to this shape. A problem facing all of these research areas is how to cope with the multivariate data from speech production experiments.
In this paper we describe techniques that provide useful tools for describing multivariate functional data such as the measurement of speech movements. Our choice of data analysis procedures has been motivated by the need to partition the articulator movement in various ways: end-effects separated from shape effects, partitioning of syllable effects, and the splitting of within-ired variation from between-ired variation. The techniques of functional data analysis seem admirably suited to the analyses of phenomena such as these. Familiar multivariate procedures such as analysis of variance and principal components analysis have their functional counterparts, and these reveal in a way more suited to the data the important sources of variation in lip motion. Finally, we found that the analyses of acceleration were especially revealing in considering the character of possible control mechanisms. Our focus is on using these speech production data to understand the basic principles of coordination. However, we believe the tools will have a more general use.