Influence of position and angulation of a voice prosthesis on the aerodynamics of the pseudo-glottis.

The use of a tracheoesophageal valve, also known as voice prosthesis, is currently the most appealing solution for recovering the ability to speak in subjects who have undergone a total laryngectomy. The prosthesis allows the passage of air from the trachea to the esophagus, thereby promoting the flow-induced vibration of the subject's pharyngoesophageal segment. In turn, the pharyngoesophageal segment modulates the air flow from the lungs into the subject's vocal tract, acting as an alternative source of acoustic energy to generate voice. The vibration of the pharyngoesophageal segment will likely depend on the aerodynamic forces acting on its wall, which will be defined by the flow characteristics downstream from the valve's outlet. Previous works have investigated the pressure drop across different prosthesis designs with both in-vitro and in-vivo experiments. Nevertheless, the aerodynamic aspects of the flow in the tracheoesophageal region have only been investigated experimentally in an idealized geometry. This work investigates the influence of the prosthesis position on the aerodynamic behavior of the pharyngoesophageal segment in terms of wall pressure distribution and characteristics of the velocity field. The investigations were carried out with a static model of the tracheoesophageal region based on the finite volume method and a Reynolds-averaged Navier-Stokes solver. The geometry of the system was based on computed tomography images obtained from laryngectomized subjects during phonation at different voice registers and included the geometry of a commercially available voice prosthesis. The results suggest that the position and angulation of the voice prosthesis have a minor influence on the pressure loss along the tracheoesophageal segment and on the pressure distribution on the pharyngoesophageal segment's wall.

Impedance measurement of non-locally reactive samples and the influence of the assumption of local reaction.

In this paper, the measurement of the absorption coefficient of non-locally reactive sample layers of thickness d1 backed by a rigid wall is investigated. The investigation is carried out with the aid of real and theoretical experiments, which assume a monopole sound source radiating sound above an infinite non-locally reactive layer. A literature search revealed that the number of papers devoted to this matter is rather limited in comparison to those which address the measurement of locally reactive samples. Furthermore, the majority of papers published describe the use of two or more microphones whereas this paper focuses on the measurement with the pressure-particle velocity sensor (PU technique). For these reasons, the assumption that the sample is locally reactive is initially explored, so that the associated measurement errors can be quantified. Measurements in the impedance tube and in a semi-anechoic room are presented to validate the theoretical experiment. For samples with a high non-local reaction behavior, for which the measurement errors tend to be high, two different algorithms are proposed in order to minimize the associated errors.