Flow field structure formed around voice prosthesis during shunt vocalization

Abstract

The shunt speech is a voice restoration method after total laryngectomy. However, the shunt speech has the disadvantage of poor voice quality. In shunt speech, the airflow characteristics of the voice prosthesis in the tracheoesophageal wall are greatly related to voice quality. In this study, we measured the flow field upstream and downstream of the voice prosthesis using PIV. And, optical measurements were made on the valves of the voice prosthesis. In conditions close to the expiratory flow rate during a speech, the flow field downstream of the voice prosthesis had an up-and-down wavy distribution, and the flow velocity in the vicinity of the downstream of voice prosthesis fluctuated with time at a frequency similar to that of the shunt voice. No temporal fluctuation was observed in the flow velocity under conditions exceeding the expiratory flow rate. Temporal fluctuations in the downstream flow field are associated with valve oscillations of the voice prosthesis. Outside the expiratory flow conditions, the valve does not oscillate, but within the expiratory flow conditions, the fundamental frequency of the valve oscillation increases as the applied flow rate increases. It was also confirmed that sound was generated from the voice prosthesis within the exhalation flow conditions. The generated sound coincided with the frequency of valve vibration and flow velocity fluctuation at each flow rate and may act as a source of the sound.

Keywords

• tracheoesophageal shunt speech
• total laryngectomy
• particle image velocimetry
• unsteady flow
• voice prosthesis
• voice rehabilitation