Vocal Physiology

Vocal Physiology

by Justine Lucas

The physiology of the voice box, or larynx, revolves around the intricate movements of its anatomical structures, which work together to produce sound. The primary mechanism behind vocalization is the vibration of the vocal cords (or vocal folds), located within the larynx. These vocal cords are controlled by several intrinsic muscles of the larynx, which adjust their tension, length, and position to modify the pitch, volume, and quality of the sound produced.

When air is exhaled from the lungs, it passes through the trachea and enters the larynx, specifically the glottis, which is the space between the vocal cords. At this point, the vocal cords are brought together by the contraction of muscles such as the lateral cricoarytenoid and interarytenoid muscles. The airflow from the lungs causes the air pressure below the vocal cords to build up, and when the pressure is strong enough to overcome the resistance of the closed vocal cords, they are forced apart. As the air passes through the narrow opening between the vocal folds, it causes them to vibrate. These vibrations are the basis of sound production.

The frequency of these vibrations, which determines the pitch of the sound, is influenced by the tension and length of the vocal cords. The cricothyroid muscle plays a key role in adjusting this tension. When it contracts, it elongates and tightens the vocal cords, resulting in higher-frequency vibrations and a higher pitch. Conversely, when the thyroarytenoid muscles relax the vocal folds, they shorten and loosen, producing lower-frequency vibrations and a lower pitch. This dynamic process allows for a wide range of pitch variation, from low to high tones.

The loudness or volume of the sound is determined by the force of the airflow from the lungs and the amount of pressure applied to the vocal cords. A greater airflow and higher pressure cause the vocal cords to vibrate more forcefully, producing a louder sound. Additionally, the movement of the arytenoid cartilages helps regulate the positioning of the vocal folds. By adjusting the space between the folds, the arytenoids contribute to fine-tuning the quality of the sound produced, such as controlling the breathiness or resonance of the voice.

In addition to pitch and volume, the resonating chambers above the larynx, including the pharynx, oral cavity, and nasal passages, modify the sound produced by the vocal cords. These structures act as resonators that amplify and shape the sound before it exits the mouth. Therefore, the entire process of voice production is a dynamic interaction between the lungs, larynx, and resonating structures, allowing humans to produce a vast array of sounds used in speech, singing, and communication.