Phonation

Phonation is one dimension of phonetic voicing. It describes the degree of glottal tension. A second dimension of voicing is timing, called voice onset time, or "VOT". (See that article.) When a sound is described as "half voiced", it may not be clear whether it is quality (phonation) or quantity (VOT) that is referred to.

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Phoneticians define phonation as "use of the laryngeal system to generate an audible source of acoustic energy, i.e., sound, which can then be modified by the articulatory actions of the rest of the vocal apparatus."

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A voiced sound is produced when an overpressure of air in the lungs causes the vocal folds to vibrate. This produces a fundamental tone accompanied by several non-harmonic overtones. The resulting sound is modified by movements in the vocal tract, by the volume of the airflow and by the degree of constriction of the folds. The vowels are usually voiced, but there are also voiced consonants.

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If the vocal folds do not vibrate, then the sound (usually a consonant) is called voiceless.

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Other sounds may be produced by completely blocking off the airstream and then releasing the folds. The sound of this type produced at the glottis is called a glottal stop.

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The voice source is used to change intonation and the tone of words by varying the subglottal pressure as well as the tension of the vocal folds. This leads to changes in the frequency of vibration, which are in turn perceived by the listener as modifications in pitch and/or in loudness. During speech the flow of air is relatively small because of constrictions of the folds.

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Subglottal pressure is regulated by a number of factors, namely: the respiratory muscles, gravity and elasticity.

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Lungs: REDIRECT Lung...

Vocal folds: The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx. They vibrate, modulating the flow of air being expelled from the lungs during phonation....

Vocal tract: The vocal tract is that cavity in animals and humans, where sound that is produced at the sound source (larynx in mammals; syrinx in birds) is filtered. In birds it consists of the trachea, the syrinx, the oral cavity, the upper part of the esophagus, and the beak. In mammals it consists of the lary...