Lungs, folds, and lips turn breath into every human voice
Talking, singing, laughing, crying: the human voice is sound shaped by the vocal tract. Three subsystems do the work. The lungs act as the pump, the vocal folds in the larynx as the vibrator, and the tongue, palate and lips carve vowels and consonants from the buzz.
Strictly speaking, voice means sound whose main source is the vibrating vocal folds, often called vocal cords. Whispering, whistling, clicks and voiceless consonants come from the same part of the body but do not count, because the folds are not doing the buzzing. For voiced sound the lungs must push enough air at enough pressure to set the folds moving, and the folds chop that stream into audible pulses. Small muscles in the larynx then alter how long and how taut the folds are, adjusting pitch and tone.
The folds themselves are flat, triangular, pearly white bands. At the rear they attach to the arytenoid cartilages, at the front to the thyroid cartilage, and their outer sides merge into the wall of the airway while the inner margins swing freely. Each has three layers: a skin-like epithelium, a ligament, and the vocalis muscle, which can shorten the fold and make it bulge. Just above sit the vestibular or false vocal folds, with a small pouch between the two pairs.
Size explains much of the gap between typical male and female voices. Men's folds usually measure 17 to 25 millimetres, women's 12.5 to 17.5, so men generally speak lower. Men also tend to have a longer vocal tract, which darkens the timbre almost independently of the folds. Singers are sorted into types: male voices from bass through baritone and tenor up to countertenor, spanning roughly E2 to E5, and female voices from contralto through mezzo-soprano to soprano, roughly F3 to C6, with extra categories used in opera.
Everything above the larynx, including tongue, palate, cheeks and lips, filters the raw sound and can even strengthen or weaken the airflow feeding it. Spoken language depends on nearly everyone in a community controlling two settings consistently: pitch, set by how fast the folds vibrate, and whether the folds are drawn together or held apart. With those tools a voice can signal anger, fear, surprise, joy or sadness, and listeners can often guess a speaker's age and sex.
Source: Human voice
