Nexus Real Silent Fans
 

These fans range from 8 to around 9.50 euros and are definitely silent enough. But if you start comparing these with the higher end Noctua fans, than they are simply no match for them. However, keep in mind that high cfm at lower decibels comes with a price tag. These Nexus fans are much cheaper than the Noctua fans we compared them with. These fans are silent at a reasonable price. So they are still a good choice if your on a tight budget.

http://www.burnoutpc.com/modules/sma...php?itemid=250