Simulation and identification of vowels based on a time-varying model of the vocal tract area function

In their purest form, vowels can be conceived as being produced with static configurations of the vocal tract shape. Laboratory measurements of both acoustic and articulatory characteristics of vowels are typically performed with this assumption. In the case of natural, connected speech, however, the vocal tract shape undergoes nearly continuous change thus a true “static” configuration is rarely produced. Listeners are able to identify vowels in this time-varying situation, often with greater accuracy than for a vowel deliberately produced without any vocal tract change. This chapter examines the time-varying changes of the vocal tract shape that produce vowel inherent spectral change. Specifically, a model of the vocal tract area function is used to investigate how time-dependent formant frequencies originate from movement of the vocal tract.