Some compressors are just plain noisy. I've worked with ones that were almost quiet, up to 'can't stay in the room with it' loud.
Couple things I did to my latest compressor that quieted it down a bit;
I put cork on the walls behind it.
I put a LARGE air filter on it. The large filter did make it quieter and for some reason it pumps up 4 lbs more. Can't figure that one out.
Put it on plastic 'feet'.
I remotely mounted it, in an 8x8 'annex' outside my garage with other things I don't want in my garage like my solvent tank, my grinder, my drill press and my table saw.
Combined it's very quiet...
With the door shut, and the garage door shut...
Unless you are in the little room with it, then it's still pretty noisy.
The cork and the big air filter (a stock one from a 4.6 Ford, custom mounted) do tone it down a bit.
Still, hammer that much air into that small a volume, it makes noise.
