Analysis of Physical Factors Influencing Acoustic Energy Distribution in the Human Voice via One-Dimensional Models

The aim of this study was to create a simplified, analytical one-dimensional (1D) computational model of the human vocal tract (VT) for the vowels [a:], [i:], and [u:]. Compared to other commonly published 1D models, this model used conical elements. In the model, the influence of steady flow and stiffness of boundary tissues is considered. The sensitivity of the transfer function to the dominant physical parameters (mouth area, resistance coefficient, steady flow, and stiffness of boundary tissues) was investigated using the created mathematical models in order to analyze the influence of these parameter combinations on acoustic energy values in the frequency spectrum. This study shows that the steady flow of the acoustic medium and the stiffness of the boundary tissues can significantly affect not only the frequency of the resonance peaks in the frequency spectrum of the VT, but also positively increase the value of total acoustic energy output of the human voice in the 2 to 3.5 kHz frequency range. The analyses show that the vowel [a:] is the more sensitive to the flexibility of the boundary tissues and the steady flow of the acoustic medium than the vowels [i:] and [u:].