Been to every home game the past 3 seasons and I can't honestly say I can tell much of a difference in the crowd noise. After a certain level I'm not sure how so many people are so convinced it's markedly quieter than before. There are some games you know aren't going to have the same buzz, like the Raiders this year, Jaguars last year.
i think the real change is that teams are prepping for it regularly rather than fitting in some things the week before they play seattle, at least in the NFC, knowing they may have to play here in the playoffs. There are obviously things you can do to combat the noise but in the past It probably wasn't worth the time spent working it into a routine game plan. Last year though, everyone witnessed how difficult it really is, and how likely it might be that Seattle (and other loud stadiums) are a true obstacle in the playoffs. I notice in general in the nfl a lot more of lines looking in at the ball and the QB doing more stomping than recent years.
Seeing teams like Seattle and Kansas City being so loud, and places like New Orleans having such a home field advantage, it's no doubt offenses will learn to adapt - and rule changes lately favoring the offense has given them some room to breath and fit in some extra work on defending against it.