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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 rarifies 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.
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. ?Xóõ has a series of nasalized click consonants in which the nasal airstream is pulmonic ingressive. Ladefoged & Maddieson (1996:268) state, "This ?Xóõ 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."
Ingressive speech sounds are produced while the speaker breathes in, in contrast to most speech sounds, which are produced as the speaker breathes out. The air that is used to voice the speech is drawn in rather than pushed out. Ingressive speech can be glottalic, velaric, or pulmonic.
Ingressive sounds occur in many languages. Despite being a common phenomenon, they are frequently associated with Scandinavian languages. Most words that are subject to ingressive speech are feedback words ("yes, no") or very short or primal (a cry of pain or sobbing). It sometimes occurs in rapid counting to maintain a steady airflow throughout a long series of unbroken sounds. It is also very common in animals, frogs, dogs, and cats (purring). In English, ingressive sounds include when one says "Huh!" (a gasping sound) to express surprise or "Sss" (an inward hiss) to express empathy when another is hurt.
Tsou and Damin have both been claimed to possess an ingressive phoneme. Neither claim has been validated to date however, and the Tsou claim has been nearly disproved. There are claims of Tohono O'odham women speaking entirely ingressively.
There are examples of ingressive sounds that belong to paralanguage. Japanese has what has been described an apicoprepalatal fricative approximant. This sound is similar to an inbreathed [s]. It is used as a response to statements that are upsetting or as a sign of deference. Japanese-speakers also use an ingressive bilateral bidental friction as a "pre-turn opening in conversation" or to begin a prayer.
Speech technologist Robert Eklund has found reports of ingressive speech in around 50 languages worldwide, dating as far back as Cranz's (1765) "Historie von Grönland" which mentions it in female affirmations among the Eskimo.
Several languages include an affirmative "yeah," "yah," "yuh," or "yes" that is made with inhaled breath, which sounds something like a gasp. That is an example of a pulmonic ingressive and is found as follows: