Regulation of phonatory efficiency by vocal fold tension and glottic width in the excised canine larynx

An excised canine larynx was used to assess the effects of glottic width and vocal fold tension on acoustic power, aerodynamic power, and vocal efficiency. Multiple regression analysis of the data obtained from 10 larynges revealed that with increased vocal fold tension there is a logarithmic decline in radiated acoustic power, while aerodynamic power remains constant (p less than .05). Vocal efficiency has a similar logarithmic decrease with increased tension (p less than .05). With narrowing of the glottis, the acoustic power increases more than the aerodynamic power delivered to the larynx, and the efficiency increases. The inverse relationships glottic width has with acoustic power and vocal efficiency are best described by a reciprocal model (p less than .01). There is a negative linear relationship between glottic width and aerodynamic power. These results suggest that within the larynx the energy conversion is regulated by glottic aperture and longitudinal vocal fold tension. The optimal width for efficiency appears to be the narrowest width that produces phonation within the modal register, whereas increased tension decreases the efficiency of the glottis.