The larynx (or voicebox) is the organ of voice in mammals. It is a tubular chamber about 2 inches high, consisting of walls of cartilage bound by ligaments and membranes, and moved by muscles. The human larynx extends from the trachea (or windpipe), the principal tube that carries air to and from the lungs.
In humans, part of the structure may protrude noticeably at the front of the neck, forming the so-called Adam's apple. It is especially prevalent in men. Within the larynx lie the vocal cords, or vocal folds, a pair of elastic folds in the lining of mucous membrane. During silent breathing, the vocal cords rest along the larynx walls, leaving the air passage fully open. During speech, the cords are stretched across the larynx; air released from the lungs is forced between the cords, causing them to vibrate and so produce what we call the voice. The articulation of these sounds results from the manipulation of teeth, tongue, palate, and lips.
Various muscles adjust the tension of the cords as well as the space between them, thus altering the pitch of the sounds produced. The more taut the cords, the higher the pitch that is produced. Since men's larynges are usually larger than women's, the longer vocal cords lead to a deeper voice than that which is generally heard in women. Growth may double the length of the vocal cords in the male adolescent, thereby leading to the "change of voice" phenomenon.