I'm a Niner fan but I come in peace!
I was listening to a radio show, and they interviewed our long snapper who has been on the team since 2000. They asked him how loud was Atlanta and if it was the loudest he'd been in since they claimed to be the loudest in the NFL. He said no it wasn't the loudest, and that it was like a regular road game. He then said that Seattle was much louder, and that it wasn't even close.
Edit - Sorry I said 6th man, I had basketball on my mind..