The Mechanism of the Human Voice: The Larynx and Respiratory System
The Mechanical Workings of the Human Voice: The Larynx and Respiratory System
The human voice, which we prize beyond any man-made instrument for its sound quality and expressiveness, can be understood scientifically as a product of the muscular interaction between parts of the human body and the air we breathe. A multitude of factors—such as a singer’s diet, posture, and even his or her sneezing and laughing patterns (Paton 43)—influence that singer’s voice and sound quality. Of these factors, two, the human larynx and respiratory systems, are basic structural components of the human body that directly support vocalization.
The human larynx is located inside the neck at the top of the windpipe and in front of the esophagus. It contains cartilage, giving it structure (“What” par. 3), and is approximately two inches by two inches in size (“What” par.1). The larynx is stimulated by “branches of the vagus nerve [. . .] on each side” (“Larynx” par.5), and an injury of the vagus nerve or of the superior laryngeal nerve that stimulates the glottis and supraglottis (the middle and top parts of the larynx, respectively) can produce weakened vocal expression, or the complete loss of one’s voice (“What” par.3; “Larynx” par. 6-7). The three basic components of the larynx include 1) the supraglottis (the top part), 2) the glottis (the central part), and 3) the subglottis (the lower part, connecting with the trachea and from there to the bronchi). Additionally, the larynx houses the Adam’s apple (a knob of cartilage at the larynx’s front) and the muscles known as the vocal chords, which reside in the glottis section (“What” par. 3). The larynx opens when we breathe and shuts when we hold our breath. When we swallow, the flap called the epiglottis closes to protect the airway and lungs from being inundated by food and liquids, instead allowing them to travel through the esophagus to the stomach (“What” par.4).
The larynx also, crucially to singers, influences the production of the human voice, or phonation. “The production of the human voice can be thought of in terms of three components: the production of airflow, the generation and resonance of sound and the articulation of voice” (“Anatomy” par.2). That “generation and resonance of sound” depends centrally on the larynx, particularly the vocal chords, or more scientifically put, “The vibration of the mucosa at the inner edge of each vocal cord” (“Anatomy” par. 4). The vocal chords, or vocal folds , the currently preferred term (Paton 41), are tiny sheets of muscle inside the larynx, with membrane at their edges and on their under surfaces (Paton 40-41). They “stretch over the top of the open windpipe [. . . and] by means of a complex musculature they can move together and apart and tip forward, back and to the side, always moving counter to each other” (ibid). This process, relatively slow in a bass voice or terribly quick in a soprano’s, creates the vibration that is human’s basic vocal tone (Paton 39). From there, resonance is developed by the vocal passageway, including the vocal folds, lips and nose, including the sinuses (Paton 39).
The respiratory system is another basic part of human vocal production, and as such, crucially connected to the larynx. The human respiratory system is our breathing mechanism. The body takes in oxygen and eliminates carbon dioxide, thus energizing the blood with oxygen, which the blood then carries to all organs and systems of the body, including the respiratory system (“Inside” par. 1). The respiratory system includes the larynx and also the sinuses, adenoids, nasal cavity, tonsils, oral cavity, pharynx, tongue, esophagus, trachea, right and left bronchia, right and left lungs, diaphragm, and pleura and pleural space. The bronchia include cilia, mucus, and cells; the lungs include bronchiole, alveoli or air sacs, and pulmonary veins (“Inside” Resp. Sys. Chart).
Breathing comes naturally to living humans, unassisted by our mothers’ bodies after being born and inhaling that first breath. Indeed, as John Glenn Paton explains, even if we were to try to stop breathing by holding our breath, “[t]he body would relax involuntarily and air would rush in” (9). Humans breathe in air through the mouth and/or nose, trachea, lungs, and diaphragm. Once in the trachea, air travels into the bronchia and then proceeds through the alveoli, then the capillaries, and then into the blood. Similarly, waste from the veins, including carbon dioxide, returns out of the body in the expiration process, beginning with the alveoli and returning through an exactly reverse process to the intake of air (“Body Systems” par. 2).
The larynx and respiratory system work together to create vocalization. A singer breathes in through the nose and mouth, and through the larynx, in a deep, relaxed manner, with lifted upper chest and open ribs and back. He needs to relax his abdominal muscles when inhaling, opening up space so that plentiful air enters into his lungs. He then breathes out slowly, using his abdominal muscles for support, keeping the diaphragm (a horizontal muscle at the lungs’ base) firmly contracted throughout the singing process, thus controlling his vocal tone. “Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness, and it is necessary for the vocal folds to produce speech” (“Larynx” par. 2). Thus, we see that the sequence of deep, full breath taken in and air then expelled from the respiratory system powerfully, steadily, and in a controlled manner utilizing the diaphragm, through the larynx and subsequently through the vocal passageway, produces the precious, beautiful human voice.
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