Low = Very quiet. High = Slightly loud and noticeable.
Interesting. What CPU + Speed? Fan settings?
i5 2500k@4Ghz and Fan at it's lowest speed (my case has a built in dial to control all the fans, as a downer I don't know at what RPM they are)
I set it up as intake in the supposed exhaust vent which might ruin your case's overall thermals but in the 600T it doesn't since there is an exhaust right on top and there is nothing hot on top besides the CPU