Vocal efficiency and aerodynamic aspects in voice disorders.

The variation of vocal efficiency for the mean values for normal subjects was investigated in patients with laryngeal disease. The relative contributions of mean flow rate and intrapulmonic pressure to the variation of efficiency were explored to explain aerodynamic aspects in voice disorders. Vocal efficiency was determined by use of expressions involving simultaneous values of sound pressure level, mean flow rate, and intrapulmonic pressure. The intrapulmonic pressure was noninvasively obtained by plethysmographic and pneumotachographic methods. Values of vocal efficiency were generally abnormally low for the types of larynges studied. An aerodynamic-biomechanical classification of laryngeal disease was inferred from the data: 1) large chink of glottis, associated with high flow rate; 2) mass on vocal fold, associated with high values of both flow rate and intrapulmonic pressure; and 3) high stiffness of vocal fold, associated with high values of intrapulmonic pressure.