A symbolic system for multi-purpose description of the mouth shapes

A multi-purpose symbolic system which can describe all of the mouth shapes conveying various kinds of linguistic information in signing, speech dialogue, and speechreading is developed, taking account of the constraints of anatomical structure and neural control and the possibility of visual discrimination. In order to make the changes in the three-dimensional shape of lips, the changes are described by four scales, namely, upward and downward heights and lateralward width of the opening of the lips, and forward and backward depths of the corners and centers. Then, the space which is composed by those scales is divided into visually discriminable parts.