A Digital Simulation of the Time-Varying Vocal Tract
P. M. Ruiz · The Journal of the Acoustical Society of America · 1971
The Kelly-Lochbaum model for the simulation of the vocal tract is based upon the solution of Webster's horn equation for a static tube. This model has been found to be adequate for the synthesis of steady vowels; however, for time-varying vocal tract shapes, the model gives rise to discontinuities in pressure and volume velocity. These discontinuities were found to produce noise in the speech synthesized by the model. A solution of Webster's horn equation for time-varying tubes was obtained by representing the vocal tract by a sequence of uniform cylindrical sections. Recursion equations for pressure and volume velocity at the junctions of adjacent sections were derived. Sentence-length utterances synthesized by this model were found to be free from noticeable noise.