loud. I get that the Seahawks weren't that great that year (and they stunk it up that game), but I always hear about how the 12th Man is so amazing -- even when the Seahawks aren't good.
The stadium was relatively loud at times, don't get me wrong. But most of the loudness came from blaring speakers trying to pump the crowd up TBH. I'm sure it gets crazy loud these days, particularly during exciting games. I'd like to go back and see another game now.