I'm going to be building a rack to hold servers, my main source of noise is from the high RPM fans in them.
I'm going to have an inner 1/4" plywood wall, about 2" of space, then an outer 3/4" plywood wall.
What would be the best material to put in the empty space between walls to lessen the fan noise?
I'm going to be using this design as a general template:
http://imgur.com/a/uh82C