The fan speed will be tied to the cpu temperature. Increasing the cpu temperature will cause the fans to speed up. You're much better off investing in a fan controller for sound management rather than relying on foam. I bought a $100 worth of foam to sound treat my case and the difference was only slightly more than negligible. My $40 scythe fan controller from 5 years ago is still going strong to this day and it's easily one of my best purchases.
10/26/14 at 2:39am