Go to groups.google.com and enter the phrase "rec.outdoors.rv-travel
generator quiet" and you'll find a couple hundred messages about your
subject. Some know what they are talking about. Check for "neon john".
Another fellow, I've forgotten his name, is a sound engineer familiar with
motorhomes. I'll copy another that was informative.

Steve
www.wolfswords.com under the motorhome link



The major flaw in your plan is that moving the genset away from your
rig puts it close to your neighbors, who probably won't appreciate it.

In my professional life before I dropped out of the rat race (the rats
were winning) I did a lot of work with VIP airplane conversions of
airliners. We made the first-class area of a 747 so quiet that the
customer bitched about the noise from the cooling fans in the
entertainment cabinet.

The main "trick" is to put absorption curtains around the source, and
to isolate the curtains from the vehicle structure. The most successful
scheme was to make an enclosure with acoustic tile mounted on honeycomb
wall board and then hang the enclosure on bungee cords from the ceiling
of the compartment in which the noise was being generated. The basic
principle is that the sound energy goes into holes the acoustic tiles
and rattles around in there while the softly suspended enclosure
isolates the sound from the vehicle.

For an RV, where cost is more critical than weight, you could do the
same using gypsum wallboard as the enclosure walls, with acoustic tile
applied to the inside surfaces. I have used this technique in a
townhouse where a new furnace was far too noisy for its location at the
top of the stairs. I figure we reduced the noise by about 70 percent.

By all means, use the best exhaust muffler you can afford, but for
mechanical vibration, an acoustic enclosure with noise-cancelling
mounts can work very well.

The ultimate solution would be an active, noise-cancelling audio
system, but that can get into mucho dollars. The concept has worked
very well on some turbo-prop airplanes. It produces opposite phase,
electronically generated noise which cancels out the source. The
drawback is that the electronics have to have about the same power as
the sound levels that penetrate the sensitive areas. Again, adequate
insulation is the key to making one of these systems work, otherwise
you need electrical power of similar magnitude to the source of the
noise.

There are many sources of information available on the Internet for
anyone wishing to pursue more details.

Frank Damp
Anacortes, WA