Abstract
In tracheoesophageal (TE) phonation, voice is produced with expiratory effort after occlusion of tracheal opening. The expiratory air introduced into the hypopharynx vibrates the mucosa where the retropharyngeal prominence comes in contract with the anterior wall. This prominence is mainly formed by thyropharyngeus muscle activity. This muscle is also reported to be activated by the expiratory act alone.
The purpose of this study is to clarify the difference in the activity the phonatory and the expiratory act under equivalent tracheal pressure, and to know the mechanism which suitably adjusts the thyropharyngeus muscle for phonation.
Examinations employed for six TE speakers are fluoroscopy, fiberscopy, and electromyography (EMG) with simultaneous aerodynamic measurements. A major difference made between two acts in fluoroscopy and fiberscopy is change in the volume of retropharyngeal prominence, which is characterized by the reduction of the craniocaudal length for phonation. Significant finding available in EMG is lower activity of the thyropharyngeus muscle for phonation than that for the expiratory act alone.
The decrease in volume and electromyographic activity of the thyropharyngeus muscle for phonation strongly suggests that TE speakers acquire a regulatory mechanism suitable for phonation by reducing its contraction. Based on this neural mechanism, they speak fluently and naturally by changing the quality and quantity of the vibratory source.
