An experimental model of the pharyngoesophageal segment in tracheoesophageal phonation.

Tracheoesophageal (TE) speech is an important method of speech rehabilitation for those who undergo a total laryngectomy. Despite the many advantages over other methods, there is still room for improvement in terms of the overall quality of the TE voice as well as its success rate. These points could be greatly assisted by an improved knowledge on the mechanics of TE speech. Here, an experimental model of the pharyngoesophageal segment (PES), based on the idea of a collapsible tube, is proposed. To implement the model, considerable simplifications had to be made, most notably in the use of a thin flexible tube to represent the PES. The model was used to assess the minimum amount of tonicity required for the onset of phonation in terms of the flow rate and longitudinal tension. Additionally, comparisons with a mathematical model [Tourinho, da Silva, dos Santos, Thomaz, and Vieira, J. Acoust. Soc. Am. 149, 1979-1988 (2021)] have been made, yielding similar trends for sufficiently large flow rates. The measurements also suggest that the phonation frequency is most affected by the tonicity of the PES, which highlights the question of which physiological mechanism is responsible for the control of the fundamental frequency of phonation.

A study on tracheoesophageal phonation based on a collapsible channel model.

Laryngeal cancer afflicts a large number of people worldwide, and some will need surgery to contain the disease. Currently, tracheoesophageal (TE) speech is a common method of voice rehabilitation for patients who have had their larynges excised. However, despite the relatively high success rate, not everyone is capable of producing the TE voice, usually due to the tonicity of the pharyngoesophageal segment (PES). The present work studies how the tonicity of the muscles of the PES affects TE phonation, focusing mainly on hypotonicity. A simplified collapsible channel model is used. Steady-state solutions are obtained and a linear stability analysis is performed. It is then shown that the steady-state solutions of the model are similar to the wide variety of possible PES configurations that are reported in the literature. The linear stability analysis results provide a simple expression for the estimation of the minimum tonicity required for self-sustained oscillations of the PES.

Numerical simulations of fluid-structure interactions in single-reed mouthpieces.

Most single-reed woodwind instrument models rely on a quasistationary approximation to describe the relationship between the volume flow and the pressure difference across the reed channel. Semiempirical models based on the quasistationary approximation are very useful in explaining the fundamental characteristics of this family of instruments such as self-sustained oscillations and threshold of blowing pressure. However, they fail at explaining more complex phenomena associated with the fluid-structure interaction during dynamic flow regimes, such as the transient and steady-state behavior of the system as a function of the mouthpiece geometry. Previous studies have discussed the accuracy of the quasistationary approximation but the amount of literature on the subject is sparse, mainly due to the difficulties involved in the measurement of dynamic flows in channels with an oscillating reed. In this paper, a numerical technique based on the lattice Boltzmann method and a finite difference scheme is proposed in order to investigate the characteristics of fully coupled fluid-structure interaction in single-reed mouthpieces with different channel configurations. Results obtained for a stationary simulation with a static reed agree very well with those predicted by the literature based on the quasistationary approximation. However, simulations carried out for a dynamic regime with an oscillating reed show that the phenomenon associated with flow detachment and reattachment diverges considerably from the theoretical assumptions. Furthermore, in the case of long reed channels, the results obtained for the vena contracta factor are in significant disagreement with those predicted by theory. For short channels, the assumption of constant vena contracta was found to be valid for only 40% of the duty cycle.