The Physics of the Human Voice
The voice is our primary mean of communication and expression. We rarely last more than a few minutes without its use whether it is talking to someone else or humming quietly to ourselves. We can use the voice artistically in many ways. For example, singing carries the rhythm and melody of speech. It creates patterns of pitch, loudness, and duration that tie together syllables, phrases and sentences. We use the voice for survival, emotion, expression, and to reflect our personality. The loss of the voice is a severe curtailment to many professions. It is affected by general body condition which is why we need to consider the location of the larynx and how that organ produces voice. Surprisingly, this complex biological design is mechanical in function. It is mechanical to the point that when it has been excised from a cadaver and mounted on a laboratory bench, the larynx produces sounds resembling normal phonation. (Titze, Principles)
The larynx, known as the voice box, consists of an outer casing of nine cartilages that are connected to one another by muscles and ligaments. There are three unpaired cartilages and six paired. The unpaired cartilages include the thyroid, cricoid, and epiglottis. The thyroid cartilage is the largest and better known as the Adam’s apple. The cricoid cartilage is the most inferior cartilage of the larynx which forms the base of the larynx on which the other cartilages rest. Together, the thyroid and cricoid cartilages maintain an open passageway for air movement. The epiglottis and vestibular folds, or false vocal chords, prevent swallowed material from moving into the larynx. The paired cartilages, accounting for the remaining six, include the arytenoid (ladle-shaped), corniculate (horn-shaped), and the cuneiform (wedge-shaped). The paired arytenoid cartilages articulate with the posterior, superior border of the cricoid cartilage. The paired corniculate cartilages are attached to the superior tips of the arytenoid cartilages. The paired cuneiform cartilages are contained in a mucous membrane anterior to the corniculate cartilages.
There are two pairs of ligaments that extend from the anterior surface of the arytenoid cartilages to the posterior surface of the thyroid cartilage. The superior ligaments are called the vestibular folds, or false vocal cords. They are covered by a
mucous membrane and, as stated above, prevent swallowed material from entering the larynx. The inferior ligaments are called the vocal folds or true vocal cords and are also covered by a mucous membrane. The vocal folds and the opening between them are called the glottis (Seeley).
Vocal folds are the primary source of sound production. As air moves past them it causes a vibration and sound. The greater the amplitude of the vibration, the louder is the sound. Thus, the force of air moving past the vocal folds determines the amplitude of vibration and loudness of the sound. It is like a...