I built a baffle box to help quiet down my air compressor. I drew up the plans in SketchUp and built it with 2x4s, OSB, and Foamular + fiberglass insulation.
SketchUp file for download: bafflebox.skp
It is a simple design that takes in the cooler air from the lower port and exhausts it through the upper port. I had toyed with the idea of adding a fan to each port, but found it was not needed after running it and checking the temperatures.
The inside was lined with Foamular except for the floor, and the wall cavities were lined with fiberglass insulation.
I ran the air lines through the top and mounted the valves and gauges on the side of the box. I also connected a hose and valve to the drain and ran it through so I can drain it without removing the door. It is much, much quieter and was definitely worth the time to build it. I went from it being so loud that I could barely hear myself think, to being able to lean right on it and have a conversation at regular volumes.