The voiceless alveolar tap or flap is rare as a phoneme. The symbols in the International Phonetic Alphabet that represent this sound are ⟨ɾ̥⟩ and ⟨ɾ̊⟩, combinations of the letter for the voiced alveolar tap/flap and a diacritic indicating voicelessness, either above or below the letter. The equivalent X-SAMPA symbol is 4_0.
Features of the voiceless alveolar flap:
Its manner of articulation is flap, which means it is produced with a single contraction of the muscles so that the tongue makes very brief contact.
Its place of articulation is dental, alveolar or post-alveolar, which means it is articulated behind upper front teeth, at the alveolar ridge or behind the alveolar ridge. It is most often apical, which means that it is pronounced with the tip of the tongue.
Its phonation is voiceless, which means it is produced without vibrations of the vocal cords. In some languages the vocal cords are actively separated, so it is always voiceless; in others the cords are lax, so that it may take on the voicing of adjacent sounds.
It is an oral consonant, which means air is allowed to escape through the mouth only.
It is a central consonant, which means it is produced by directing the airstream along the center of the tongue, rather than to the sides.
The airstream mechanism is pulmonic, which means it is articulated by pushing air solely with the lungs and diaphragm, as in most sounds.
A tapped fricative is in effect a very brief fricative, with the tongue making the gesture for a tapped stop but not making full contact. This can be indicated in the IPA with the lowering diacritic to show full occlusion did not occur.
Tapped fricatives are occasionally reported in the literature, though these claims are not generally independently confirmed and so remain dubious.
Flapped fricatives are theoretically possible but are not attested.
Features of the voiceless alveolar tapped fricative:
Its manner of articulation is tapped fricative, which means the tongue makes a brief obstruction sufficient to create frication.
Its place of articulation is apical alveolar, which means it is articulated with the tip of the tongue at the alveolar ridge.
Its phonation is voiceless, which means it is produced without vibrations of the vocal cords. In some languages the vocal cords are actively separated, so it is always voiceless; in others the cords are lax, so that it may take on the voicing of adjacent sounds.
It is an oral consonant, which means air is allowed to escape through the mouth only.
It is a central consonant, which means it is produced by directing the airstream along the center of the tongue, rather than to the sides.
The airstream mechanism is pulmonic, which means it is articulated by pushing air solely with the lungs and diaphragm, as in most sounds.
Reported from Turkish in a single source. A " voiceless apico-alveolar flap with variable friction" is reported as the word-initial allophone (and one of four word-final allophones) of /r/ in Kobon. It is also reported from Afenmai, where it is the "tense" equivalent of "lax" [ɾ].
