A Thermoacoustically-Driven Vocal Tract Model

Over centuries, different mechanical methods have been used to mimic the sounds of the human vocal tract. Arai's three-tube sliding model is recreated to demonstrate the formant frequencies of human vowel sounds. Physiologically, this project is designed to imitate vowel formants determined by tongue position for several vowels. The source of the sound energy in this model is sound produced by heat via the thermoacoustic effect in a standing wave. The model has a sliding constriction piece that represents the tongue, a single open end to represent the mouth, and a closed end to represent the glottis. Resonances of the vocal tract act as a filter of the vocal folds and create what are called formant frequencies. Which formants resonate most strongly sheds light on how the vocal tract may promote one dominant frequency over another as determined by the tongue placement and constriction. A one-dimensional wave equation is used to calculate the formant frequencies as a function of the tongue position. By analyzing the peak frequencies from the FFT spectrum, the more dominant modes were compared to the mathematical model. The model's results can assist with speech therapy and diagnosis.