If it makes any difference, there were a few years when the Lance generators had a real muffler attached. That muffler makes the noise level very tolerable.
I say this because a friend has a 2003 Lance and the generator has the muffler kit.
I don't know the year in which Onan made the change, but the generators switched to a "spark arrestor" type muffler and is very loud.
And they cannot easily be retro-fitted to the old style muffler.
Your Lance may have the old muffler'd generator and it'd be a shame to loose that in my opinion.