212 Evo keeps fluxing


Aug 1, 2011
I have an i5-2500k, but not OCed. I was playing Anno 2070 today and my 212 evo seemed to keep fluctuating alot. One moment it would be going full blast and be really loud, while the next it would calm down and get quite (not idle quite just more so then before). Is this normal or is there something I can do that would help it stay constant? I know I can make it stay a current rpm through the motherboard controls but I don't much like the idea due to the potential of me setting it wrong..
Just let it do its thing. It's not THAT loud, lol (I have one and run it a constant 100% more times than not, and it's nowhere near as loud as the two fans on my GPU can get, even when they're at 40%).

Fan noise doesn't bother me AT ALL, though because I prefer better cooling performance over silence, but to each their own, I suppose.