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The football-shaped button sits in the lower right corner, and does precisely what you feared: It produces the dreadful vuvuzela sound.
If you haven't been following the World Cup and you're not familiar with the term "vuvuzela," it's a plastic horn that produces a loud monotone that takes all of about five seconds to get on your nerves.
Oh well. BZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ!