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In phonetics, initiation is the action by which an air-flow is created through the vocal tract. Along with articulation, it is one of the two mandatory aspects of sound production: without initiation, there is no sound. The means of initiating a phone is called its airstream mechanism.
Initiation may be divided into pressure and suction. In the former, the organ performing the initiation—called the initiator—builds up pressure within the vocal tract, creating an outward airflow. In the latter, the initiator reduces pressure within the vocal tract, creating an inward airflow. Phones pronounced with pressure initiation are called egressive, and those pronounced with suction initiation are called ingressive.
There are three initiators in spoken human languages, the lungs/diaphragm, the glottis, and the tongue, for six possible airstream mechanisms. Four of these are found in 'normal' words around the world:
- pulmonic egressive, where the air is pushed out of the lungs by the ribs and diaphragm; all human languages employ such sounds (such as vowels), and many, such as English, use them exclusively.
- glottalic egressive, where the air column is pushed upward by the glottis. Such consonants are called ejectives.
- glottalic ingressive, where the air column is rarefied as the glottis moves downward. Such consonants are called implosives.
- velaric ingressive, AKA lingual ingressive, where the air in the mouth is rarefied by a downward movement of the tongue. These are the clicks.
The Khoisan languages have pulmonic, ejective, and click consonants, the Chadic languages have pulmonic, implosive, and ejective consonants, and the Nguni languages utilize all four, pulmonic, click, implosive, and ejective, in normal vocabulary.
In interjections, other initiations may be employed. For example, in Canada, Sweden, Turkey, and Togo, a pulmonic ingressive ("gasped" or "inhaled") vowel is used for back-channeling or to express agreement, and in France a velaric/lingual egressive (a "spurt") is used to express dismissal. The only language where such sounds are known to be contrastive in normal vocabulary is the ritual language Damin; however, that language appears to have been intentionally designed to be different from normal speech.
Pulmonic initiation Edit
Initiation by means of the lungs (actually the diaphragm and ribs) is called pulmonic initiation. The vast majority of sounds used in human languages are pulmonic egressives. In most languages, including all the languages of Europe, all phonemes are pulmonic egressives.
The only attested use of a phonemic pulmonic ingressive is a lateral fricative in Damin, a ritual language formerly used by speakers of Lardil in Australia. This can be written with the extended version of the International Phonetic Alphabet as [ɬ↓]. !Xóõ has ingression as a phonetic detail in one series of its clicks, which are ingressive voiceless nasals with delayed aspiration, [↓ŋ̊ʘʰ ↓ŋ̊ǀʰ ↓ŋ̊ǁʰ ↓ŋ̊!ʰ ↓ŋ̊ǂʰ]. Peter Ladefoged considers these to be among the most difficult sounds in the world. Other languages, for example in Taiwan, have been claimed to have pulmonic ingressives, but these claims have either proven to be spurious or to be occasional phonetic detail.
In interjections, but not in normal words, pulmonic ingressive vowels such as [ə↓] occur in languages as diverse as Swedish and Ewe. In Ewe, [ə↓] is used for back-channeling, to indicate that one is listening (like ah or I see in English).
Glottalic initiation Edit
It is possible to initiate an airflow in the upper respiratory tract by means of the vocal cords or glottis. This is known as glottalic initiation.
To perform glottalic pressure initiation, one lowers one's glottis (as if to sing a low note), closes it as if for a glottal stop, and then raises it, building up pressure in the upper trachea and oral cavity. Glottalic egressives are also called ejectives. Since the glottis must be fully closed to form glottalic egressives, it is impossible to pronounce voiced ejectives.
To perform glottalic suction initiation, the sequence of actions performed in glottalic pressure initiation is reversed: one raises one's glottis (as if to sing a high note), closes it, and then lowers it to create suction in the upper trachea and oral cavity. Glottalic ingressives are also called implosives.
It is usual for implosives to be voiced. Instead of keeping the glottis tightly closed, it is tensed but left slightly open to allow a thin stream of air through. Unlike pulmonic voiced sounds, in which a stream of air passes through a usually-fixed glottis, in voiced implosives a mobile glottis passes over a nearly motionless air column to cause vibration of the vocal cords. More open phonations than modal voice, such as breathy voice, are not condusive to glottalic sounds because in these the glottis is held relatively open, allowing air to readily flow through and preventing a significant pressure difference from building up behind the articulator.
Because the oral cavity is so much smaller than the lungs, vowels and approximants cannot be pronounced with glottalic initiation. So-called glottalized vowels and other sonorants use the more common pulmonic egressive airstream mechanism.
Velaric initiation Edit
The third form of initiation in human language is velaric or lingual initiation, where a sound is produced by a closure at two places of articulation, and the airstream is formed by movement of the body of the tongue. Velaric stops are more commonly known as clicks, and are almost universally ingressive.
To produce a velaric ingressive airstream, first close the vocal tract at two places: at the back of the tongue, as in a velar or uvular stop, and simultaneously with the front of the tongue or the lips, as in a coronal or bilabial stop. These holds may be voiced or nasalized. Then lower the body of the tongue to rarefy the air above it. The closure at the front of the tongue is opened first, as the click "release"; then the closure at the back is released for the pulmonic or glottalic click "accompaniment" or "efflux". This may be aspirated, affricated, or even ejective. Even when not ejective, it is not uncommon for the glottis to be closed as well, for a triply articulated consonant, and this third closure is released last to produce a glottalized click. Clicks are found in very few languages, notably the Khoisan languages of southern Africa and some nearby tongues such as Zulu. They are more often found in extra-linguistic contexts, such as the "tsk tsk" sound many Westerners use to express regret or pity (a dental click), or the clucking noise used by many equestrians to urge on their horses (a lateral click).
Velaric egressive initiation is performed by reversing the sequence of a velaric ingressive: the front and back of the tongue (or lips and back of the tongue) seal off the vocal cavity, and the cheeks and middle of the tongue move inward and upward to increase oral pressure. The only attested use of a velar egressive is a bilabial nasal egressive click in Damin. Transcribing this also requires the use of the Extended IPA, [ŋʘ↑].
Since the air pocket used to initiate velaric consonants is so small, it is not thought to be possible to produce velaric fricatives, vowels, or other sounds which require continuous airflow.
Clicks may be voiced, but they are more easily nasalized. This may be because the vocal cavity behind the rearmost closure, behind which the air passing through the glottis for voicing must be contained, is so small, clicks cannot be voiced for long. Allowing the airstream to pass through the nose enables a longer production.
In nasal clicks, the velum is lowered so as to direct air through the nasal cavity. This nasalization is pulmonic, and as it involves a second airstream, it may itself be egressive or ingressive, independently of the nature of the rest of the click. Nasal clicks may be voiced, but are very commonly unvoiced and even aspirated, which is rare for purely pulmonic nasals.
- Eating the Wind: a satirical, but illustrative example of sound symbolism and iconicity of airstream mechanisms.
- he:מנגנון זרימת אוויר
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