Human voice

The sounds a person makes with their vocal tract—like talking, singing, laughing, crying, screaming, shouting, humming, or yelling—are what make up the human voice. This type of sound production relies on the vocal folds (also called vocal cords) as the main source of sound, though other noises from the same area, such as unvoiced consonants, clicks, whistling, and whispering, come from different mechanisms. The voice is created through three main parts working together: the lungs act as a pump to push air, the vocal folds inside the larynx vibrate to produce audible pulses, and the articulators (tongue, palate, cheeks, lips, and other parts above the larynx) shape and filter that sound. The larynx’s muscles adjust the length and tension of the vocal folds to fine-tune pitch and tone, while the articulators can also strengthen or weaken the airflow. Together, the vocal folds and articulators can produce highly complex sounds, and the tone of voice can be modulated to show emotions like anger, surprise, fear, happiness, or sadness. The voice also reveals a speaker’s age and sex, and singers use it as a musical instrument.

Adult men and women typically have different-sized vocal folds because their larynxes differ in size. Men’s voices are usually lower-pitched, with larger folds measuring between 17 mm and 25 mm in length; women’s folds range from 12.5 mm to 17.5 mm. These folds sit inside the larynx, attached at the back to the arytenoid cartilages and at the front to the thyroid cartilage. Their inner edges are free to vibrate, and they have a three-layer structure: an outer epithelium, a vocal ligament, and the vocalis muscle, which can shorten and bulge the folds. They are flat, triangular bands that are pearly white in color. Above each vocal cord is the vestibular fold (or false vocal cord), with a small sac between its two folds. The size difference leads to different voice pitches, and genetic variation within each sex creates singing voice types: for men, these include bass, bass-baritone, baritone, baritenor, tenor, and countertenor (ranging from about E2 to E5 and higher); for women, contralto, alto, mezzo-soprano, and soprano (ranging from F3 to C6 and higher). Additional categories exist for operatic voices. Beyond the folds, men generally have a larger vocal tract, which gives their voices a lower timbre, independent of the folds themselves.

In spoken language, people dynamically adjust two key parameters of the laryngeal voice source: pitch (based on how fast the vocal folds vibrate) and the degree of separation between the folds (adduction or abduction). The ability to quickly vary this separation has a strong genetic component, as it helps keep food from entering the lungs, and the muscles controlling it are among the fastest in the body. Children can learn to use this action consistently in speech before age two, simply by listening to adults around them, even though the laryngeal movements are invisible. If an abductory or adductory movement is strong enough, the vocal folds stop vibrating (or never start). A sound with an abductory gesture is called voiceless, though listeners often identify it by the change in spectral qualities rather than the absence of vibration. Similarly, an adductory gesture can be called a glottal stop even if the folds don’t fully stop vibrating. Other aspects of the voice, like variations in vibration regularity, also play a role.