Anybody know the quietest PC Case Fan?

What do you think is the most effective and quietest PC Case Fan.. as i am in need of the lowest possible DbA... but also do not want a shitter.. any help?

preferably a 120mm/140mm

Your best bet would be to go with a delta PC fan and a speed controller. You can get them at frozencpu.com They put out the most CFM out of any PC fan I have ever used plus with a fan controller you can control the db and cfm.