I have been wondering the same thing about making these switches quieter. They sound like a jet engine. There are two fan speeds, normal and turbo. They boot in turbo and then fall back to normal, but even normal is crazy loud.
It doesn't make sense that these switches need a lot of fan because they don't draw that much power (216W max, 106W typical), and the power they do draw is spread across a number of components in the switch.
I actually purchased some additional fans to see if I could come up with a way to quiet the fans. I was thinking about putting a resistor in-line with the fan power wire. I haven't had a chance to actually do testing yet, but will have to come up with something because I need my 40Gig speeds, in my house! The only other alternative is to sound-proof the wiring closet these are in, but that is a pain too...
If anyone has other good ideas, I would love to hear them...