"Without a doubt, these are the quietest fans I have used to date. A standard enclosure can hold up to three 120mm fans generating 30dBA plus each. That makes for a very noisy situation. The NF-S12's in U.L.N.A. will generate around 1/5th of that. Just imagine these fans cooling a radiator in a watercooling setup; now that would be an ultra quiet PC. "
FULL STORY @ VIRTUAL-HIDEOUT (http://www.virtual-hideout.net/reviews/Noctua_NFS-12/index.shtml)