How the Larynx (Voice Box) Works

Our voices originate from an organ in our neck called the larynx, or voice box. The larynx is a short passageway that lies in the front of the neck connecting the throat (pharynx) with the windpipe (trachea). The walls of the larynx are formed by nine pieces of cartilage that is a flexible but strong connective tissue of the body found in places such as the end of the nose and the top of the ear. Cartilage provides strength and structure while at the same time retaining some flexibility.

The two front pieces of cartilage of the larynx are fused and form the "Adam’s apple" that protrudes in the front of the neck. The Adam’s apple is often more pronounced in human males because male sex hormone during puberty influence its growth.

The interior of the larynx consists of a region called the glottis. During swallowing, a large, leaf-shaped piece of cartilage (the epiglottis) moves downward to cover the glottis and close it off to prevent food and liquids from "going down the wrong way." The glottis includes a pair of folded membranes, the vocal folds (or vocal cords), and the space between the folds through which air passes from the lungs. Above the vocal folds is a second pair of folded membranes, often called the false vocal cords.

Photo of a normal larynx looking down at the glottis from the top.
Front of larynx (throat) is toward top of picture, back of larynx toward the bottom.

The false vocal cords can be brought together to hold breath against pressure in the chest. This often happens when we strain to lift heavy objects. They also close during swallowing to protect the glottis.

The vocal folds, or true vocal cords, and the space between them are involved in sound production or phonation. The vocal folds have many elastic ligaments that stretch between pieces of rigid cartilage. Muscles of the larynx attach to the cartilage and to the folds. When these muscles contract, they pull the ligaments tight and stretch the folds into the airway, making the airway passage smaller. Air that is forced from the lungs through this narrow passage causes the stretched folds to vibrate. The vibrations set up sound waves that travel through the larynx and are amplified by the throat, mouth and cranial sinuses.

If the vocal folds are stretched very taught, they vibrate rapidly and the sound produced is high-pitched. When producing lower-pitched sounds, the vocal folds are somewhat relaxed and therefore vibrate more slowly as the air strikes them. Men tend to have lower pitched voices than women because male sex hormones at puberty cause the vocal folds to become thicker. Thicker folds are not able to vibrate as rapidly.

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