Two muscular folds in the larynx, behind the Adam's apple. They are very flexible, and are brought together to impede the airflow during speech, when they vibrate and produce voice, used in the articulation of vowels and many consonants. They are also used to vary the pitch of the voice (generally, the faster the vibration, the higher the pitch) and are also involved in the production of several distinctive tones of voice. When they are completely open, the air flows freely, as in whispering and the pronunciation of ‘h’.