This is backwards. The stadium was MUCH louder in the 4th quarter than at any other time in the game. On the Giants' final drive, it was deafening the whole time, everyone in the stadium was standing, and on third downs it was a madhouse.
If you're going based off of what you hear on TV, then I think you get a skewed view. In the pre-game they're mic'ed down on the field trying to pick up all the external noise. During the game, they're trying to do a broadcast, so I imagine they have ways of dampening what you hear over the air so you can actually hear the announcers.
It was very loud. I've been to plenty of games, including big college games like the Red River Shootout, and it was every bit as loud as those, if not louder at times.
Does anyone who was actually at the game think that it wasn't loud?