The bilabial clicks are a family of click consonants that sound like a smack of the lips. They are found as phonemes only in the small Tuu language family (currently two languages, one down to its last speaker), in the ǂ’Amkoe language of Botswana (also moribund), and in the extinct Damin ritual jargon of Australia. However, bilabial clicks are found paralinguistically for a kiss in various languages, including integrated into a greeting in the Hadza language of Tanzania, and as allophones of labial–velar stops in some West African languages (Ladefoged 1968), as of /mw/ in some of the languages neighboring Shona, such as Ndau and Tonga.
The symbol in the International Phonetic Alphabet that represents the place of articulation of these sounds is ⟨ʘ⟩. This may be combined with a second letter to indicate the manner of articulation, though this is commonly omitted for tenuis clicks. An uncommon non-IPA phonetic symbol for bilabial clicks is a turned b with hook, ⟨ɋ ⟩.[1]
In official IPA transcription, the click letter is combined with a ⟨kɡŋqɢɴ⟩ via a tie bar, though ⟨k⟩ is frequently omitted. Many authors instead use a superscript ⟨kɡŋqɢɴ⟩ without the tie bar, again often neglecting the ⟨k⟩. Either letter, whether baseline or superscript, is usually placed before the click letter, but may come after when the release of the velar or uvular occlusion is audible. A third convention is the click letter with diacritics for voicelessness, voicing and nasalization; it does not distinguish velar from uvular labial clicks. Common labial clicks are:
The last is what is heard in the sound sample at right, as non-native speakers tend to glottalize clicks to avoid nasalizing them.
Damin also had an egressive bilabial [ʘ↑], which may be an egressive click (if it is not buccal) and which is always followed by another consonant ([ɲ], [ŋ] or [pj]).[2]
The basic articulation may be voiced, nasal, aspirated, glottalized, etc.
The forward place of articulation is labial, which means it is articulated with the lips. The release is a noisy, affricate-like sound. Bilabial articulation, using both lips, is typical. Sometimes this may pass through a labio-dental stage as the click is released, making it noisier.[3] In other cases, the lower lip may start out in contact with both the upper teeth and the upper lip.[4]
Clicks may be oral or nasal, which means that the airflow is either restricted to the mouth, or passes through the nose as well.
Because the sound is not produced with airflow over the tongue, the central–lateral dichotomy does not apply.
The airstream mechanism is lingual ingressive (also known as velaric ingressive), which means a pocket of air trapped between two closures is rarefied by a "sucking" action of the tongue, rather than being moved by the glottis or the lungs/diaphragm. The release of the forward closure produces the "click" sound. Voiced and nasal clicks have a simultaneous pulmonic egressive airstream. (One of the two labial clicks in Damin is lingual egressive, which means that the trapped air pocket is compressed by the tongue until it is allowed to spurt out through the lips.)
The labial clicks are sometimes erroneously described as sounding like a kiss. However, they do not have the pursed lips of a kiss. Instead, the lips are compressed, more like a [p] than a [w], and they sound more like a noisy smack of the lips than a kiss.
Symbol
The bullseye or bull's eye (ʘ) symbol used in phonetic transcription of the phoneme was made an official part of the International Phonetic Alphabet in 1979, but had existed for at least 50 years earlier. It is encoded in Unicode as U+0298ʘLATIN LETTER BILABIAL CLICK.
The superscript IPA version is U+107B5𐞵MODIFIER LETTER BILABIAL CLICK.[5]
Similar graphemes consisting of a circled dot encoded by Unicode are:
A symbol called a turned b with a tail was created and is used in older publications.[citation needed] It was never widely used and was eventually dropped for ʘ. Still the deprecated IPA character is encoded at U+024BɋLATIN SMALL LETTER Q WITH HOOK TAIL. Earlier it is privately encoded by SIL International at U+F211<private-use-F211> and is available in SIL supporting fonts.[6]
Occurrence
English does not have a labial click (or any click consonant, for that matter) as a phoneme, but a plain bilabial click does occur in mimesis, as a lip-smacking sound children use to imitate a fish.
Labial clicks only occur in the Tuu and Kx'a families of southern Africa, and in the Australian ritual language Damin.
Labial clicks may have arisen historically from labialization of other places of articulation. Starostin (2003)[7] notes that the ǂ’Amkoe words for 'one' and 'two', /ʘ̃ũ/ and /ʘoa/, have labial clicks whereas no other Khoisan language has a labial consonant of any kind in its words for these numerals, and Starostin (2007)[8] and Sands reconstruct a series of labialized clicks in Proto-Kxʼa, which became labial clicks in ǂ’Amkoe. In Hadza, the word for 'kiss', /ǀ̃ua/, becomes a mimetic /ǀ̃ʷa/ or /ʘ̃ʷa/ in greetings.[9]
