We're in 2571 and 2573 next December, so I'm interested in reports too. We're actually under the atrium though. I don't know how much noise from the restaurants actually filters down, but it's probably not much.
For what it's worth, we've had late seating on 2 cruises, and most people are out of dinner by 10 or 10:30. I'd imagine that there's probably 45 minutes to an hour of cleanup at most, so there shouldn't be any Triton related noise after 11:30. It's got to be better than under the nightclub section, which will probalby go til 2 at least.