Determination of the Shape of the Human Vocal Tract from Acoustical Measurements

In recent years there has been considerable interest in the modelling of speech production in terms of the motion of the articulators. This interest has stimulated work on the determination of the shape of the human vocal tract as a function of the utterance. For frequencies less than 3500 Hz, wave motion in the vocal tract is essentially planar, so that the shape is effectively specified by the cross-sectional area as a function of distance from one end of the tract (say from the glottis). During the past two decades X-ray techniques have been used to determine these area functions. These techniques suffer from two major drawbacks: (?) In order to keep the exposure to X-rays within safe dosage limits, only a small number of measurements can be made on any one subject; (ii) The interpretation of X-ray data is a complex and difficult art, and a number of assumptions must be made in order to convert this data to area functions. The accuracy with which area functions are reconstructed is rather limited. 1195