Robert,
I assume your Class A is a diesel pusher?
You might be willing to use a gas genset if your motorhome's engine was gas, and hence fed by a large gas tank that also fueled the generator - like our Class C. ;)
You do have a point. The quietest RV generator setup I've ever experienced was a Class A parked close to us once that was making only a slight very, very low level humming sound. I walked right up to within, maybe 5 feet of it, to find out what the quiet sound was - it was their amazing diesel generator. I assume it might have been a water-cooled generator and one of those diesel generators that turns at only a constant 1800 RPM, instead of 3600 RPM. Nice!