My testing process for this cooler is simple: for load temperatures, I will use LinX to load the processor for 30 minutes. The idle temperatures will be measured after 30 minutes of inactivity on the system.
Here are the specifications of the test system I'll be using:
Processor: AMD Phenom II X2 555 @ 3.2 Ghz
Memory: Crucial Ballistix DDR3-1333 @ 6-6-6-20-1T
Motherboard: Jetway HZ03
Hard Drive: Seagate ST3500410AS 500GB
Graphics: Integrated Radeon HD 4250 (128MB SidePort DDR3 in use only)
As you can see, the idle temperatures don't change much, if at all between the low and high fan speeds. However, at load, turning the fan up to max speed shaves off 4 degrees. With temperatures this low, there is quite a bit of overclocking that can be done before approaching a dangerous temperature.
The fan is almost silent on low, but quite audible at the high speed setting. However, the sound seems to be only the sound of air moving and not any mechanical motor sounds or vibrations. At any rate, unless you are overclocking, in which case you should be prepared for noise, keeping the fan speed on low is no problem in regards to the CPU temperatures.