Voice

Voice Production: Phonation

Phonation -

In phonetics, this is the process by which the vocal folds produce certain sounds through periodic vibration. In engineering acoustics and linguistics, it is referred as any sound made during a speech. Simply, it is the production of voiced sounds. Such sounds are created when the exhaled air stirs the vocal folds into vibration.

Structure and Function of the Phonatory Mechanism The phonatory process, or voicing, occurs when air is expelled from the lungs through the glottis, creating a pressure drop across the larynx. The oscillation of the vocal folds serves to modulate the pressure and flow of the air through the larynx, and this modulated airflow is the main component of the sound of most voiced phones. The larynx mat be raised or lowered through the action of certain extrinsic muscles. One such muscle connects the larynx to the hyoid bone and during swallowing pulls the larynx upward and slightly forward so that it presses against the back of the tongue; this raising action of the larynx also exerts a pull upon the opening of the esophagus, enlarging it so that it receives more easily the food and drink that pours over the top of the protected larynx. One theory for which vibration is initiated is stated by the myoelastic theory: when the vocal cords are closed and breath pressure is applied to them, the cords remain closed until the pressure beneath them is sufficient to push them apart, allowing air to escape and reducing the pressure enough for the muscle tension to pull the folds back together again. Alternation in the position and tension of the vocal folds is provided by the action of certain intrinsic muscles. The most important of the intrinsic muscles are the vocal folds themselves, which are called the thyro-arytenoid muscles. During vegetative breathing, the folds are relaxed, leaving a triangular opening (glottis). During certain other biological activities, as well as during phonation, the glottis must be closed to permit the building up of air pressure in the trachea. The closing of the folds is accomplished by the integrated action of various intrinsic muscles which cause the arytenoids cartilages to slide together and to pivot inwardly on their ball and socket-like attachments. These movements bring the folds together so that their edges touch, effecting a closed valve. To open the glottis, other muscles pull the arytenoids cartilages apart and rotate them outwardly. In phonation, the edges are brought lightly together so that they touch throughout their complete length. This closure must be sufficiently tight to prevent the escape of any air except that representing genuine thoracic pressure. It should be not so tight, however, that it precludes the free excursions of the folds when set into motion by breath. When the force of the air stream becomes strong enough to overcome the resistance of the folds and the air pressure above them, the folds are forced apart and a puff of air escapes between them, setting their inner edges into vibration. The puff of air, converted into a wave of condensation and rarefaction by the movement of the folds, continues up the throat and out the mouth and/or nose. Immediately after the puff of air has passed between the folds, the pressure below the

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glottis drops and the glottis is quickly closed. After the pressure has been re-established, it forces again the folds apart and another wave is produced. If this alternate opening and closing occurs more rapidly than about fifty times a second, a vocal tone is produced. When phonation is concluded, intrinsic muscles return the arytenoids to their original station, thus separating the folds.

Importance of Phonatory Mechanism in Good Voice Production 1.

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The phonatory mechanism helps to determine the pitch of the voice. a. When the folds are shortened or lengthened, the pitch tends to be raised or lowered accordingly. b. An increased thickness of the folds tends to produce a lowered pitch and a decreased thickness a raised pitch. c. Because changes in length and thickness tend to neutralize each other, changes in the tension of the folds are possibly the most important single agent in altering pitch. The phonatory mechanism helps to determine the voice quality. a. Pleasant quality can be produced only by elastic, healthy vocal folds possessing sufficient tension to effect close approximation, but free from excessive tension. b. Flabby, inelastic folds allow too much air to escape between them during phonation, causing a husky, breathy tone. c. Excessive tension in either the intrinsic or extrinsic muscles or in the larynx produces harshness or hoarseness.

Degrees of Phonation 

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Voiceless (full airstream) describes the pronunciation of sounds when the larynx does not vibrate. The International Phonetic Alphabet has distinct letters for many voiceless and modally voiced pairs of consonants (the obstruents), such as [p b], [t d], [k g], [q] [f v], and [s z]. Breathy voice (murmur, soughing, or susurration) is a phonation in which the vocal cords vibrate, as they do in normal voicing, but are held further apart, so that a larger volume of air escapes between them. A stop with breathy-voiced is like aspiration in that it delays the onset of full voicing. This is the phonation of the Hindi "voiced aspirated stops": bh, dh, jh, and gh. There are also breathy-voiced vowels. Modal voice (maximum vibration) is the vocal register used most frequently in speech and singing in most languages. It is also the term used in linguistics for the most common phonation of vowels. It is the only phonation found in the vowels and other sonorants (consonants such as m, n, l, and r) of most of the languages of the world, though a significant minority contrasts modal voice with other phonations. Among obstruents (consonants such as k, g, ch, j, s, and z), it is very common for languages to contrast modal voice with voicelessness. Slack voice (lax voice) describes the pronunciation of consonants with a glottal opening slightly wider than that occurring in modal voice. In some Chinese languages and in many Austronesian languages, the 'intermediate' phonation of slack stops confuses listeners of languages without these distinctions. Stiff voice describes the pronunciation of consonants with a glottal opening narrower, and the vocal cords stiffer, than what occurs in modal voice. Creaky voice (restricted airstream) sometimes called laryngealisation, pulse phonation, vocal fry or glottal fry, is a special kind of phonation in which the vocal folds are compressed rather tightly,

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becoming relatively slack and compact. Although creaky voice may occur with very low pitch, as at the end of a long intonation unit, it can occur with any pitch. Glottalized voice (blocked airstream) is the complete or partial closure of the glottis during the articulation of another sound. Glottalization of vowels and voiced consonants is most often realized as creaky voice (partial closure). Glottalization of voiceless consonants usually involves complete closure of the glottis; another way to describe this phenomenon is to say that a glottal stop is made simultaneously with another consonant. In certain cases, the glottal stop can even wholly replace the voiceless consonant. Faucalized voice, also called hollow or yawny voice, is the production of speech sounds with an expanded laryngeal cavity. It contrasts with harsh voice, in which the larynx is compressed. Harsh voice, also called ventricular voice or pressed voice, is the production of speech sounds (typically vowels) with a constricted laryngeal cavity, which generally involves epiglottal coarticulation. It contrasts with faucalized voice, which involves the expansion of the larynx. A whisper is an unvoiced mode of phonation in which the vocal cords do not vibrate normally, but are instead adducted sufficiently to create audible turbulence (a 'hissing' quality) as the speaker exhales (or occasionally inhales) during speech. This is a somewhat greater adduction than that found in breathy voice. Falsetto refers to the vocal register occupying the frequency range just above the modal voice register and overlapping with it by approximately one octave. Both men and women can phonate in the falsetto register. The term falsetto is most often used in the context of singing to refer to a type of vocal phonation that enables the singer to sing notes beyond the vocal range of the normal or modal voice.

References Armstrong, Eric, Phonation. Retrieved January 18, 2008 from yorku.ca/earmstro/journey/phonation.html Caparas, Ma. Veronica G., et al., Readings for Communication III. Quezon City, Philippines: Publisher’s Printing Press. Phonation. Retrieved January 14, 2008 from en.wikipedia.org/wiki/Phonation Voice Production. Retrieved January 14, 2008 .eduweb.vic.gov.au/edulibrary/public/ohs/voicepro.pdf

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