Modeling tongue-palate contact patterns in the production of speech

Previous studies on lingual movements in speech have led to the assumption that the tongue can be divided into a small number of functional blocks. This work was aimed at finding out whether subdivision into independent components may also be observed in patterns of tongue-palate contacts, as revealed by electropalatography (EPG). An attempt was made to reduce EPG data to a small number of articulatorily relevant parameters in an empirical way, and to model the configuration of the linguo-palatal contacts in speech as a combination of these parameters. Our corpus was composed of ten natural sentences recorded by two female native speakers of French. EPG data reduction was first performed by a feedforward multilayer neural network, and then by factor analysis. The results showed that variation in the tongue-palate contact pattern mainly occurred along two dimensions, related to lingual contacts in (1) the alveolar region, and (2) the palatal region, respectively. These results were consistent for both subjects, and provided evidence for the hypothesis that the tongue tip/blade and the tongue dorsum are two independently controllable articulators. In a second step, potential applications of this empirical model to studies of coarticulation and timing are illustrated through a pilot investigation of /kl/ clusters. Finally, implications of our work for a comprehensive model of tongue movements are discussed.