Generators are hella loud,
Most of my neighbors have EM generators running natural gas.
Not much noise at all.
NG or propane, dual fuel generators sound the same.
A newer diesel installation should not be much different?
Last winter we lost power for a few days and the phone/cable company set up a small diesel about 200 yards from my position, no noticeable sounds.
The dogs and I stopped by to inquire about our lost internet service.
Some unnamed locals running an old generator or two they drug out of the garage... Have you ever heard a squadron of the old A-1 Skyraiders on takeoff???
I have an older 7.5KW 2 cylinder Kohler that is as quiet as anything built today. While under full load I cannot hear it when I stand 60 feet away.
I *DID* modify the exhaust slightly, but the mechanical noises are still as quiet as can be.