vocal cords

n. The vocal cords (also vocal folds) are two folds of flesh housed in the larynx and surrounding the glottis. Muscles in the larynx pull the vocal cords apart (abduct) during breathing, opening the glottis and allowing air to enter and escape from the lungs through the trachea. During phonation (in the production of voiced sounds, such as vowels and voiced consonants), the vocal cords move together (adduct). The increased subglottal pressure forces air through the vocal cords, causing them to move apart. The rush of air at the same time decreases pressure, by Bernoulli's principle, moving the vocal cords together again. This cycle takes place in rapid sequence – on average, 125 Hz (cycles per second) in adult males, 200 Hz in females, 300 Hz in children; these differences are linked to differences in the size of the larynx, the length and mass of the vocal cords, and the length of the vocal tract. The result of the cyclical opening and closing of the vocal folds is voicing, or phonation, in speech production or singing: a fundamental frequency is generated that will be modulated as it travels through the vocal tract. – EMF