Generator Compartment Soundproofing
Before Soundproofing Mod
After Soundproofing Mod
Generator compartment with soundproofing material installed (high-res image). Note that the air intake on the door is offset from the air intake on the generator and the soundproofing above the generator for additional noise reduction. There are four layers of soundproofing material (2") under the generator to raise it up to clear the frame structure. The material was purchased from Lowes and is called "Sound Board" stock number 15387. I think it is made by Dow and has appears to be self extinguishing when a source of flame is removed. Please note that this generator installation is an LP device, and therefore the risk of fuel soaking into the material is low. For the installation of a gasoline or diesel generator, additional fire rating research is suggested. A noise reduction of 9db was achieved by this modification as measured by a Radio Shack Digital-Display Sound-Level Meter Model 33-2055.
An Onan exhaust resonator was also added to the installation (hig-res image). While Onan claims only 1 db of noise reduction from the resonator, the effect is more significant because the resonator removes the harshness from the noise. If you listen to the exhaust from a very close distance, all you hear is a very muffled "put, put, put". Most all of the remaining noise is engine and generator mechanical noise transmitted directly from the generator housing, which is reduced by the soundproffing material shown above.