AcoustiFan No Dust Quiet Fans
 

If you are one of those people that hate any little bit of noise
and want your computer as silent as possible, than this review is for you.
We all know that dust increases a fan's noise over time. Put that new quiet
fan in, and a couple of months later it is a little louder than it used to
be. That is why AcoustiFan has developed a dust free fan. It is designed to
eliminate that gradual increase in noise over time of a fan. Quiet PC was
nice enough to send us a couple for review.

Link: http://www.atruereview.com/acoustifan/index.php