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 voice & speech source

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voice & speech: journey of the voice: phonation: physiology

Laryngeal Physiology: How it works

Understanding how the structures of the larynx work is a complicated process as it works aerodynamically, in response to the breath stream flowing through the glottis. Once you understand how the stream of air is chopped up to make the waves of sound, it is quite simple to grasp the different ways in which that sound can be modified to change the pitch (i.e., singing high or low), the intensity (volume) or to switch registers.

How Vibration Happens

The Bernoulli Effect
is the scientific principle the draws the vocal folds together. The Bernoulli Effect is all around us. It is the main principle of lift, which causes airplanes to fly, and baseballs to spin.

A simple example of how the Bernoulli effect works is experienced by a bicycle commuter everyday: riding along, a large truck passes her. Its speed creates an area of lower pressure, it draws in the surrounding air as it passes the cyclist, and she feels as if she is being sucked toward the truck -- in fact she is! Another example is found in the tap in a highschool science lab. The flow is constricted in a very narrow nozzle. Above the nozzle is a small hole, which draws in air to create a vacuum in experiments.

The vocal folds are also drawn in by the Bernoulli Effect. The intrinsic muscles of the larynx bring the vocal folds together, they "approximate" them, so that the space between the folds, the glottis, is essentially closed off. Once they are closed, the air stream creates a pressure against the closed vocal folds until they are blown apart. As the air rushes through the very narrow, constricted opening, it must accelerate to get through. This high speed air, much like the truck in the example above, creates suction perpendicular to the direction of its flow -- it draws the side of the opening in.

"The Wave" - the simultaneous actions of the vocal folds and the mucosal wave
The vocal folds move in a wave-like manner, opening and closing in three dimensions:

Pitch Change

Intensity Change
If frequency (pitch) is the number of waves of high and low pressure, intensity is the size of the wave, which controls "volume". As we get louder:

Modes of Vibration
Regular or Modal: sometimes called chest-tone

Falsetto: sometimes called head-tone

Glottal Fry:

Thumbnail of the registers table
Registers tend to mean the type of voice, especially in singing, though the name may refer to the mode of vibration in some writings. The Registers Chart helps to explain and visualize the various traditional voice types and to compare where the modes shift.

There are three kinds of attacks (or beginning of the each voiced sound):


Back to Phonation

Back to The Journey of the Voice



More on Phonation Physiology

The Bernoulli Effect
The Exploratorium puts it in simple terms and explains it by floating a ball on a stream of air. posted May 26, 98.

A Sound Judgement
A web site promoting an excellent program to teach people to hear the difference between healthy voices and impaired ones. Features great information on perceptual components of voice, including pitch, intensity, and a number of qualities. posted May 27, 98.