phonation

Phonation. The voice is produced when the closed, taut vocal folds in the position of phonation are opened and made to vibrate by an air stream expelled from the lungs, causing sound waves to be produced. The volume of sound depends on the force of the air stream, and the pitch is determined by the frequency of vibration. The latter depends on the length (sex and age differences), tension and thickness of the vocal cords, as in the strings of a musical instrument.