Formant frequencies for incrementally varying vocal tract

In order to gain a better understanding of the relationships between vocal tract configurations and their corresponding acoustic characteristics, the formant frequencies for an incrementally varying vocal tract were investigated by use of a vocal tract model. A transmission line analog of the vocal tract was simulated on a digital computer, taking all the losses within the vocal tract and the lip radiation effect into account. A vocal tract configuration for a vowel was represented by a 34-section area function, and the difference in the area functions for two vowels were linearly interpolated to represent the dynamics of the vocal tract. Between the two neighboring interpolated area functions, the formant frequencies were computed by changing two contiguous sections at a time. Dependence of the formant frequencies on particular parts of the vocal tract and the sensitivity of the formant frequencies to the change in the vocal tract shape were investigated.