I've recently replaced my fans (CPU, GPU, and bought a CHA fan). The GPU remained the same, but I've seen it when it was spinned 2 times faster, than it usual... but it is rarely.
The problem is, that the CPU fan in Windows (especially 7) spinned too much, 'cos it keeps in under 40°C, and it is spinning with 3300-3600 RPM, which is too high I think. If I swich to Ubuntu, it keeps on ~40-45°C with with 2500-2800 RPM, which is a big difference in numbers, and in noise.
I'm looking for a manual fan control solution, or just reduce the Windows' multipliers of fan speed control, somehow... I was bought the new fans because of the lower noise (and it does it, but not with 3.6k RMP).