The voiceless retroflex trill is a sound that has been reported to occur as an allophone of /ʂ/ in the Maldivian language. Although the tongue starts out in a sub-apical retroflex position, trilling involves the tip of the tongue and causes it to move forward to the alveolar ridge; this means that the retroflex trill gives a preceding vowel retroflex coloration the way other retroflex consonants do, but the vibration itself is not much different from an alveolar trill. Thus, the narrower transcription ⟨ɽ͡r̥⟩ is also appropriate.
Features of the voiceless retroflex trill:
- Its manner of articulation is trill, which means it is produced by directing air over the articulator so that it vibrates.
- Its place of articulation is retroflex, which prototypically means it is articulated subapical (with the tip of the tongue curled up), but more generally, it means that it is postalveolar without being palatalized. That is, besides the prototypical sub-apical articulation, the tongue contact can be apical (pointed) or laminal (flat).
- 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.