Ingressive sound

In phonetics, ingressive sounds are sounds by which the airstream flows inward through the mouth or nose. The three types of ingressive sounds are lingual ingressive or velaric ingressive (from the tongue and the velum), glottalic ingressive (from the glottis), and pulmonic ingressive (from the lungs). The opposite of an ingressive sound is an egressive sound, by which the air stream is created by pushing air out through the mouth or nose. The majority of sounds in most languages, such as vowels, are both pulmonic and egressive. Lingual ingressive, or velaric ingressive, describes an airstream mechanism in which a sound is produced by closing the vocal tract at two places of articulation in the mouth. This rarefies the air in the enclosed space by lowering the tongue and then releasing both closures. Such sounds are called "clicks". Glottal ingressive is the term generally applied to the implosive consonants, which actually use a mixed glottalic ingressive–pulmonic egressive airstream. True glottalic ingressives are quite rare and are called "voiceless implosives" or "reverse ejectives". Pulmonic ingressive describes ingressive sounds in which the airstream is created by the lungs. These are generally considered paralinguistic. They may be found as phonemes, words, and entire phrases on all continents and in genetically-unrelated languages, most frequently in sounds for agreement and backchanneling. Some pulmonic ingressive sounds do not have egressive counterparts. For example, the cell for a velar trill in the IPA chart is greyed out as not being possible, but an ingressive velar (or velic) trill is a snort. Pulmonic ingressive sounds are extremely rare outside paralinguistics. A pulmonic ingressive phoneme was found in the ritual language Damin; its last speaker died in the 1990s. ǃXóõ has a series of nasalized click consonants in which the nasal airstream is pulmonic ingressive. Ladefoged & Maddieson (1996:268) state, "This ǃXóõ click is probably unique among the sounds of the world's languages that, even in the middle of a sentence, it may have ingressive pulmonic airflow.