Page "Phonation" Paragraph 4

Fundamental frequency, the main acoustic cue for the percept pitch, can be varied through a variety of means.

Large scale changes are accomplished by increasing the tension in the vocal folds through contraction of the cricothyroid muscle.

Smaller changes in tension can be effected by contraction of the thyroarytenoid muscle or changes in the relative position of the thyroid and cricoid cartilages, as may occur when the larynx is lowered or raised, either volitionally or through movement of the tongue to which the larynx is attached via the hyoid bone.

In addition to tension changes, fundamental frequency is also affected by the pressure drop across the larynx, which is mostly affected by the pressure in the lungs, and will also vary with the distance between the vocal folds.

Variation in fundamental frequency is used linguistically to produce intonation and tone.