Voice box anatomy. Computer artwork showing the location (right) and structure (left) of a human larynx (voice box). The larynx is involved in breathing, sound production (phonation), and protecting the trachea against food aspiration. It houses the vocal folds (vocal cords), which are essential for phonation. They open (far left) during breathing, close when holding one's breath, and vibrate to modulate the flow of air being expelled from the lungs for phonation.