Ours is under the bed (5500) and it's not loud at all. AC is way louder. I can still nap with both on though. We're in a 5th wheel though so there's some space between the bed and the generator. I'm not sure we'd ever leave our generator on all night long though, even in the warmer places we camp, it cools off at night.
In our old bumper pull Raptor though, we had a 4000 directly under the bed and it was much louder, and it made the bed itself warm. Great when it's cold out, not so much in the summer, especially for a mid afternoon snooze :)