South Park: Season 3, Episode 17

3 - 17: Worldwide Recorder Concert (a.k.a. The Brown Noise)

Mr. Garrison takes his class to Arkansas to perform in a worldwide recorder concert. Cartman spends the bus ride trying to find the "brown noise" - a pitch which causes people to lose bowel control. Once they arrive, Mr. Garrison confronts his father about the lack of molestation in their family, and the boys get in a verbal battle with some kids from New York.