Determining vocal tract shape by applying dynamic constraints

This paper describes our approach to determining the shape of the human vocal tract from the acoustic speech signal. A digital filter model of the vocal tract, which is specified by the locations of six articulatory structures, was examined to determine the set of acoustic signals that can be synthesized. The synthetic acoustic signals were classified by the frequency locations of the first three formant peaks. A sensitivity analysis was performed to determine an appropriate quantization of the vocal tract parameters. A structured table was generated which allowed the vocal tract parameter values to be determined from the set of formant values. A human glide utterance, /ai/, was analyzed to determine the formant locations of contiguous data segments. Using these values, possible vocal tract shape candidates were found from the table. From the total set of candidates occuring over the duration of the utterance, the set of vocal tract shapes that resulted in the minimum parameter variance was determined. It is shown that this minimum variance set, corresponding to a minimum movement of the articulators, produces a reasonable vocal tract shape trajectory for the utterance.