My Ultimaker 2 fan seemed noisy.
A little spacer for the extruder fan to help reduce the turbulence noise and to increase the air flow over the heat ...sink. I designed it so you can reuse the 2 screw you removed from the fan. This mod makes the air flow over the heat sink easier and it will cool the extruder better. It may also help with dual extuders, I have not tested it on dual extuders but I think it will work.
12-aug-14 I have added another version of the Fan Mod to help it print on the UM2 (it's a bit more solid).
3d model print parameters
A little bit of ABS and you can reuse the parts you have....