Originally Posted by Don Landis
Have an onboard Olan 4000 generator, and I'd like to better sound proof it, with some kind of external sound barrier and then maybe some internal sound barrier materials. Is that possible, and if so what does it look like and what materials should I use?
There are limits to the soundproofing you can do, because you need to maintain adequate air circulation to allow the engine to breathe and cool itself.
So if you want to soundproof the generator enclosure, make sure you do not decrease the size of any openings. But each solid surface can have sound-deadening materials attached to the interior and/or exterior surfaces. The most effective thin
material is a sheet of lead completely encased in foam, frequently used on sailboats with auxiliary engines in order to muffle engine noise. Here's a link that can give you more information…
There are lead-free barriers as well, but they tend to be thicker to get the same attenuation.
On another note, you can add a resonator to the exhaust system, if it doesn't already have one— that's in addition to a muffler, by the way. A resonator for an Onan generator only provides about a 3dB reduction, but that's the same as cutting the sound volume in half. But that only helps on the noise heard outside
From inside, much of the sound is transmitted by vibration directly to the vehicle frame through the generator mounts, so the resonator doesn't make it quieter inside the vehicle. If you have rigid generator mounts, you can replace them with vibration-isolating mounts, but then you have to carry that on through to any exhaust pipe mounts as well or else the exhaust pipe will rattle when the generator vibrates on its new mounts and the exhaust pipe is prevented from vibrating by rigid hangers.