In many of the languages that contain the voiced bilabial trill, it only occurs as part of a prenasalised bilabial stop with trilled release, [mbʙ]. This developed historically from a prenasalized stop before a relatively high back vowel, such as [mbu]. In such instances, these sounds are usually still limited to the environment of a following [u].
The manner of articulation (how the sound is produced) is trill. This means that this sound is produced by directing air over the articulator so that it vibrates. In most instances, it is only found as the trilled release of a prenasalized stop.