Figure 1-3. The larynx.
b. The larynx serves two functions and has two sets of muscles--one for each
(1) One set controls the size of the glottis. Thus, it regulates the volume of
air passing through the trachea.
(2) The other set controls the tension of the vocal cords. Thus, it produces
vibrations of selected frequencies (variations in pitch) of the moving air used in the
process of speaking.