Loud
It would seem to me that when you’re dressed like this, you don’t really need to hold a sign reading ‘loud noises’ to attract attention. When you can’t come up with anything clever to write on your sign, you can’t go wrong with loud noises. After all, that’s the message you’re trying to convey – loud noises, simple as it is!
Sometimes, at sport events, it seems as if the goal is to be as loud as you can, and it doesn’t even matter what you’re shouting. There’s too much noise to make out any coherent sentences anyway, so the point is to make as much noise as possible, to let your team know you’re there and you’re prepared to shout your heart out for them. The real competition in the stadium isn’t between the teams, but rather which fans are louder.