Outdoor stadiums are known to be the loudest. Not domes. I think it's due to the reverberation in the dome causing some noise to cancel itself out. I'm no expert, though.
Not surprising at all. They've done it time and time again to end halves over the last 3 seasons. It's clinical what they do. Like always managing to have a time out left when they get into the red zone. It's by design.