There is no such thing as a really quiet genny. In an otherwise quiet CG the sound is going to carry a considerable distance. True, the ECO gennys are far better than the contractor types which, IMO, have no business being in a CG of any sort except maybe the infield of a NASCAR track.
It involves a little thought but a good way to eliminate the sound of others gennys is to run your own when the neighbours run theirs.
A run in the morning to recharge from overnight & power whatever for breakfast. A run in the evening at dinnertime for whatever is needed & a battery top off for the night.
If everyone runs at the same time, nobody notices the other guys noise.