Bilabial trill

The 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 ʙ.

In many of the languages where the bilabial trill occurs, it occurs only 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].

(只有少數語言將此音視為獨立音素。在絕大部分情況，它只是作為前鼻化雙唇塞音的顫動除阻，讀音是 [mbʙ]。在歷史上，這是由較高的後元音緊接前鼻化輔音演變出來，例如[mbu]。這讀音僅出現在數種語言，而且往往限于這類情況才出現。例子有在馬努斯島東邊使用的Kele語中的[mbʙuen]「它的果實」。)

PS.老師說小時候有心理創傷ㄉ人~沒辦法發這ㄍ音.
這ㄍ論點是否成立還是會被推翻~~有機會ㄉ話找ㄍ人做做實驗吧!!!

from:http://en.wikipedia.org/wiki/Bilabial_trill