for surfers and benefit of others:
Cowbells are sometimes popular noisemakers at sporting events, despite attempts to suppress them. In the United States, they are most closely identified with Mississippi State University, whose football fans smuggle in cowbells by the thousands despite a ban on artificial noisemakers by its conference, the Southeastern Conference. Worldwide, in Cross-Country Skiing, cowbells are often rung vigorously at the start and finishes of races. Cornell ice hockey fans who are also known for their zealous support of their team have cheers that feature use of a cowbell while in Lynah Rink.
http://en.wikipedia.org/wiki/Cowbell