Recently, my ~1 year old Mac Pro has been audibly noisier. There's a low, quiet but distinctly mechanical spinning sound that's essentially always audible. Doing a little bit of diagnostic work, I *think* it's the intake fan - spinning all the other fans up doesn't produce much of an audible change in the sound, but spinning the intake fan up makes the sound (which is separate from the usual "fast spinning fan" noise) speed up. The RPMs aren't unusual though, and the temperatures in the system are well within normal ranges. I've tried opening up the case and blowing dust out, but that doesn't seem to have done much. Any other suggested fixes? Is this something to be actively worried about?