http://www.frozencpu.com/products/23410/fan-1303/Aerocool_DS_120mm_x_25mm_Dead_Silent_Cooling_LED_Fan_-_Blue.html?tl=c331s518b13&id=NntG5wqI
The Aerocool DS 120mm x 25mm Extreme Cooling Fan is one of world’s most silence fans with breakthrough technology and innovation. These fans come with dual-layered fan blades - combination of plastic and rubber fan blades to absorb “wind” noise. The “Golf Ball” surface design on the back rubber side of the fan blades is to minimize the air turbulence. The fan frame incorporates four silencer blocks and anti-vibration rubber pads on each mounting hole. Along with the silent treatment these fans also have a super low starting voltage of 3V making them great for controllers.