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In phonetics, the airstream mechanism is the method by which airflow is created in the vocal tract. Along with phonation and articulation, it is one of three main components of speech production. The airstream mechanism is mandatory for sound production and constitutes the first part of this process, which is called initiation. The organ generating the airstream is called the ''initiator'' and there are three initiators used in spoken human languages: * the diaphragm together with the ribs and lungs ''(pulmonic'' mechanisms), * the glottis ''(glottalic'' mechanisms), and * the tongue ''(lingual'' or ''"velaric"'' mechanisms). Though not used in any language, the cheeks may be used to generate the airstream ''(buccal'' mechanism, notated in VoQS). See buccal speech. After a laryngectomy, the esophagus may be used as the initiator (notated for simple esophageal speech and for tracheo-esophageal speech in VoQS). See esophageal speech. ''Percussive'' consonants are produced without any airstream mechanism. ==Types of airstream mechanism== Any of the three initiators − diaphragm, glottis or tongue − may act by either increasing or decreasing the pressure generating the airstream. These changes in pressure often correspond to outward and inward airflow, and are therefore termed ''egressive'' and ''ingressive''. Of these six resulting airstream mechanisms, four are found lexically 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 nearly three out of four use them exclusively. * ''glottalic egressive,'' where the air column is compressed as the glottis moves upward. Such consonants are called ejectives. Ejective and ejective-like consonants occur in 16% of the languages. * ''glottalic ingressive,'' where the air column is rarefied as the glottis moves downward. Such consonants are called implosives. Implosive and implosive-like consonants occur in 13% of the world's languages. Despite the name, the airstream may not actually flow inward: While the glottis moves downward, pulmonic air passes outward through it, but the reduction in pressure makes an audible difference to the sound. * ''lingual ingressive,'' AKA ''velaric ingressive,'' where the air in the mouth is rarefied by a downward movement of the tongue. These are the click consonants. Clicks are regular sounds in ordinary words in fewer than 2% of the world's languages, all in Africa.〔Ian Maddieson (2008) "Presence of Uncommon Consonants". In: Martin Haspelmath & Matthew S. Dryer & David Gil & Bernard Comrie (eds.) ''The World Atlas of Language Structures Online.'' Munich: Max Planck Digital Library, chapter 19. Available online at http://wals.info/feature/19. Accessed on 18 January 2011〕 These mechanisms may be combined into airstream contours, such as clicks which release into ejectives. 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. Most other languages utilize only one or two airstream mechanisms. In interjections, the other two mechanisms may be employed. For example, in countries as diverse as Sweden, Turkey, and Togo, a pulmonic ingressive ("gasped" or "inhaled") vowel is used for back-channeling or to express agreement, and in France a 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 extinct ritual language Damin (also the only language outside Africa with clicks); however, Damin appears to have been intentionally designed to differ from normal speech. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Airstream mechanism」の詳細全文を読む スポンサード リンク
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