Generator Noise

The bulk of the noise from our Onan 4K generator is cooling air flow noise, not noise out of the exhaust pipe. This air flow noise reflected outward from the sides of your rig varies by what kind of surface you are parked on.

Also, some motorhomes do not have their Onan generators mounted up high enough into their outside compartment. If your Onan is hanging down such that you can see a little bit of the bottom of it from the side of your rig, the outside noise from it will be greater.

With a properly mounted Onan up into a completely enclosed (except for the bottom) outside compartment, noise can be improved by lining the inside of the compartment walls with sound absorbing material and by replacing the vibration mounts with high performance ones.

Noise from your Onan inside your rig depends upon any sound insulating material that you put inside it's compartment, as mentioned in the above paragraph - PLUS - whether or not the Onan is under your rig in an area inside your rig that is lightly or heavily carpeted.

Here's a couple of links to good sound absorbing material and better vibration mounts:

http://www.marinefoam.com/marine-grade-ultra-barrier-plus.html

http://www.avproductsinc.com/index.html

For what it's worth, a poster in these forums quite some time ago had worked extensively on their RV's Onan compartment and gotten their outside noise readings down to around 55 dB. I don't remember what the distances were for their sound measurements, but probably some persistent searching on past posts over a year old would produce the thread.