Role of the thyroarytenoid muscle in regulation of fundamental frequency

Thyroarytenoid muscle activity is shown to combine with cricothyroid muscle activity to regulate fundamental frequency of phonation. The relative amount of activity in these muscles, as measured electromyographically, is illustrated on a muscle activation plot (MAP) for four subjects vocalizing at different pitches and loudnesses. Electrical stimulation of the thyroarytenoid muscle in various regions of the MAP suggests that both positive and negative changes in fundamental frequency (F0) can occur with increased thyroarytenoid activity. At lower fundamental frequencies and lower vocal intensities, F0 correlates positively with thyroarytenoid activity, but at higher fundamental frequencies and low intensity (especially in falsetto voice) an increase in thyroarytenoid activity tends to lower F0. A biomechanical body-cover model of fundamental frequency control is used to explain this phenomenon.