As mentioned earlier, make sure it is isolated regarding the mounting. In reality it is likely isolated as far as mounting goes, but you may need to improve upon that. Also, I've used duct liner from Heating and A/C shops for many years to use as sound deadening. Comes in 1/2" and 1" thicknesses. HVAC shops will also likely have the stick on pins to help hold it in place til the contact cement sets. Another option, though possibly pricey-er would be to use the high density foam that is used to make "ergo-pads". That stuff would work great, though I'm not sure how you'd source enough of it in sizes large enough for the compartment that wouldn't leave your wallet hemorrhaging. Then there is always the possibility of different options to get thru the night w/o the unit running
