Hiding Generator Noise...

[Bill B]

Waaaaaay back when I was in the Army we had 5kw diesel generators that were fairly loud. A conversation while standing next to it had to be shouted.
Being in a S & S company we had to have the generators running. To quiet them we dug a pit deep enough so that the top of the generator was about 24 inches below ground level. We then applied overhead cover like you would for a foxhole or a bunker, leaving a gap on one side for ventilation. On the other side was the entrance to the bunker.
The side that had the entrance was loudest, you could hear the gen. from about 50 feet. On the other sides you had to be within 20-30 feet to hear it good enough to localize the sound, past about 50 feet you couldn't hear squat.
The larger generators (15-30 kw) were trailer mounted and had sound proofing kits installed. Basically it was a box that went around the generator made from sheet steel, on the inside was 3/4 inch of open-cell foam covered by heavy aluminum foil.
While it didn't make them silent by any stretch of the imagination, it did reduce the noise by about 50%. Another thing we did, on occasion, was to build sandbag walls around the generators. Not as effective as putting them in a pit, but pretty useful.