Originally Posted by Foiled Again
(snip)Bi-labial fricative - George Carlin's definition. (form lips into tight circle, place tongue forward, blow air making noise that might come from one's nether lip)
Sounds like a Carlin! Actually, Carlin has been good to linguistics; he's one of several well-known folks to appear in an excellent series about human languages
As for "raspberry," it is a noun, one of whose meanings is "a derisive or contemptuous sound made by vibrating the extended tongue and the lips while exhaling." That meaning seems to be related to the verb "to razz [somebody]" ("To deride, heckle, or tease"). The relevant sound ("z") that he may be referring to would be a voiced alveolar fricative
Just ask a linguist! You'll get more than you ever wanted to hear!