The voiceless bilabial trill is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨ʙ̥⟩. The X-SAMPA symbol is B\_0

This sound is typologically extremely rare. It occurs in languages such as Pará Arára^[1] and Sercquiais.^{[citation needed]}

Only a few languages contrast voiced and voiceless bilabial trills phonemically – e.g. Mangbetu of Congo and Ninde of Vanuatu.^[2][3]

There is also a very rare voiceless alveolar bilabially trilled affricate, [t̪͡ʙ̥] (written ⟨tᵖ̃⟩ in Everett & Kern) reported from Pirahã and from a few words in the Chapacuran languages Wariʼ and Oro Win. The sound also appears as an allophone of the labialized voiceless alveolar stop /tʷ/ of Abkhaz and Ubykh, but in those languages it is more often realised by a doubly articulated stop [t͡p]. In the Chapacuran languages, [tʙ̥] is reported almost exclusively before rounded vowels such as [o] and [y].

Additionally, Lese has another rare trilled affricate, a labial–velar trilled affricate [k͡pʙ̥], which occurs as an allophone of the voiceless labial–velar plosive [k͡p].^[4]

Features of the bilabial trill:

• Its manner of articulation is trill, which means it is produced by directing air over an articulator so that it vibrates.
• Its place of articulation is bilabial, which means it is articulated with both lips.
• 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.
• Because the sound is not produced with airflow over the tongue, the central–lateral dichotomy does not apply.
• Its airstream mechanism is pulmonic, which means it is articulated by pushing air solely with the intercostal muscles and abdominal muscles, as in most sounds.