I built a cabinet to reduce the sound of my BFL 60GH/s miner. It has three chambers insulated with foam. There are four 120mm intake fans pulling cool air in from the floor and another four pushing out the back at the top. I built a little power supply for the fans that draw 15 W. I had hoped to sit the miner vertically pushing air upwards but it won't run that way.

The temperature is about 2-3 deg C higher which I will work on. 59 on the floor is now 63 C in the cabinet. It is significantly quieter and I expect to be able to sleep now.

 http://subjectreality.com/miner/cabinet.png