They have never hid that the coverings were designed to do two things - keep rain out for 70% of the seats and to keep noise in
However, you need to make noise to have it kept in and Seattle does an excellent job at that. They set the record this past weekend for noise at a live sporting event topping 136 decibels on an official reading - takes more than an overhang to do that.
Keep in mind the Kingdome was always the loudest place in the league - going back to 1983 Dan Reeves was complaining about the noise in the dome after getting bounced in the playoffs
The "noise rule" that the NFL put in was largely due to issues opposing teams had getting plays in at the kingdome
If you look at Husky Stadium it is also very loud - Autzen can get going as well a state to the south
While it definitely gets louder on 3rd down and at the line there are 3 things that help make the stadium loud - the first is that it's now the cool thing to do, the 2nd ties in to the 1st in that the team has created a great environment - from the blue thunder drumline performing outside before the game and in the game, the 12 flag, the hawk flying out of the tunnel leading the team, fans get pumped - the 3rd is the fans really believe they can make an impact and cheer during the huddle, during all downs, it's just constant noise
With the Behring ownership and the changes in Seattle during that same time that shifted the dynamic of the city so much was lost from the environment during the 80s - however, the ownership group has done a fantastic job bringing so much of that back
A far cry from when I went there for the 1st game in that stadium - a loss against the cardinals - in which they needed local businesses and a deadline extension to avoid a blackout and the place was quiet .... I went hoarse yelling at others .... it's grown so much sense then
The seahawks support a local fan who videotapes the games from his seats and host his videos on their webpage .... he records and adjusts the volume to a -3 setting to try and smooth it, but it still comes off pretty loud
Their stadium isn't in the top 20 in stadium capacity for the league - but louder than the larger, covered wonder in dallas and a lot of other covered buildings ..... you also have to balance the overhangs with the fact that they don't cover the entire lower level, they don't cover the endzones and one endzone is fairly open to the outside with relatively fewer seats that sit above the pricey field level boxes
As mentioned, TV just doesn't do that place justice when it's rocking - anytime the defense is on the field you can't have any type of normal conversation around you - you have to scream at the person right next to you and they probably aren't going to be able to hear you ........... it's great