"Another importnat factor to achive silent operation is the use of a a high quality frictionless noiseless bearings incorporated inside the fan motor,
such as (FDB) Fluid Dynamic Bearings, & SSO bearings. The type of bearings inside a high-end fan motor are exceptional quality and will guarantee
silent operation as well as reduce vibration and provide a long life span. For example these high-end bearings are found in Thermalright (FDB) Fluid
Dynamic Bearing Fans & Noctua SSO bearing Fans."
As far as fans go, the most efficient and highly recommended fans are Yate Loons. Go here http://www.petrastechshop.com/
and search Yate Loons. Yate Loon's are some of the better fans out there in my opinion, and they have different models so you can chose if you want LED's or not and higher / lower CFM or higher / lower DBa.
A notice to EVERYONE who has posted here with a computer problem, I highly encourage you to keep current with the forums, even if it's browsing for 10-15 minutes during lunch, or before you go to bed at night. There are many things that you can learn and apply to future issues. My goal is to help people get to a point where they can use their own knowledge to help themselves, and others.
Also please use the search button. You've got a 50/50 chance that someone's asked your question and we've answered it.