The sound that all of the adults make when they talk on Charlie Brown cartoons. (It actually sounds like it's coming from a trombone or a trumpet.)

It's actually a muted trumpet making the sound. It's a brilliant theatrical device to make the adults in the Peanuts world irrelevant. It's also useful when you're trying to describe someone who's talking but not saying anything, especially if they're in the room while you're doing it.

Also useful for mimicing the speeches of university administrators.