QUANTITATIVE MEASURES OF THE PALATE USING ENHANCED ELECTROPALATOGRAPHY

Electropalatography (EPG) is a useful tool for investigating tongue dy namics in experimental phonetic research and speech therapy. However, data provided by EPG are a two-dimensional representation in which all absolute positional information is lost. This paper presents an enhan ced EPG (eEPG) system which uses digitised palate shape data to displa y the tongue-palate contact pattern in three dimensions. The palate sh apes are obtained using a colour-encoded structured light three-dimens ional digitisation system. The three-dimensional palate shape is displ ayed on a Silicon Graphics workstation as a surface made up of polygon s represented by a quadrilateral mesh. EPG contact patterns are superi mposed on to the three-dimensional palate shape by displaying the rele vant polygons in a different colour. By using this system, differences in shape between individual palates, apparent on visual inspection of the actual palates, are also apparent in the image on screen. Further , methods have been devised for computing absolute distances along pat hs lying on the palate surface. Combining this with calibrated palate shape data allows accurate measurements to be made between contact loc ations on the palate. These have been validated with manual measuremen ts. In addition, vocal tract areas in the oral cavity have been estima ted by using the absolute measurements on the palate for a given conta ct pattern, and assuming a flat tongue profile in the uncontacted area .