Asetek Vapochill Micro
 

Both the Extreme and High-end version are so quiet that you can barely hear them if you put your ear right next to the fan - but this results in seriously degraded cooling performance. While the Low-noise fan is a bit louder, it is still unbelievably quiet on the low-speed setting.
At the high-speed setting the Extreme Performance fan sounds like a vacuum cleaner, reminds me of GeforceFX times. The high-end fan is still a bit loud, but the low-noise fan comes out with a very acceptable sound level.

http://www.techpowerup.com/reviews/A...pochillMicro/4

no comparison or reference HSF tested :(