Does anyone know a place to get the Charlie Brown teacher voice sound?

Hey guys, I'm working on a project for t.v. productions and i really need to get the Charlie Brown Teacher voice. You know the one that goes waa waa waa and all that. Does anyone know a website, or have a link, to get this sound?
Update: I need it in a file. I can't make it with a trombone or with my mouth.
Update 2: I don't wanna know what makes the noise, if its funny, or what you think of the voice, i just need a site or link like that one guy. thx
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