Listen to this: an interview with The Linguists
(Below is text almost directly from the wiki, something I don't usually do, but it's so charmingly, accidentally, sexy.)
A bilabial fricative is a phone whose place of articulation is bilabial (with both lips) and whose manner of articulation is fricative. There are two bilabial fricatives, neither of which appears in standard English. The voiced bilabial fricative (IPA: [β]) is a sound similar to English v, but with the air going between the lips. It is used for the Spanish letters b and v, as well as in other languages. The voiceless bilabial fricative (IPA: [ɸ]) is a sound similar to English f, but also made between the lips. It appears in the Japanese sound romanized as f or h, as well as in other languages. The two sounds, as well as the two labiodental fricatives, are used contrastively in Ewe.
George Carlin incorrectly used the phrase bilabial fricative to refer to the sound of blowing a raspberry which is correctly called a linguolabial trill (except as performed by chimpanzees). Jack Black also incorrectly used the phrase bilabial fricative [...]. He was actually referring to a repeated voiced labial plosive, often used as part of his vocal warm up.