I just got this new Mac Pro yesterday. It sounded fairly quiet on start-up but over the past day I have noticed a high-pitched noise that seems to change its intensity and pitch with the fan speed on PCI using Istat Pro. At first I noticed while viewing photos and then watching a short video that I could hear a clearly revving up noise that became rather high pitched. After trying to listen to different areas of the tower (haven't opened it up yet) it was rather difficult to pinpoint the source. I don't think it is the large fans in front or back, but I am far from an expert. I then noticed that when I heard this noise revving up, which happens quite quickly, as if one was putting pressure on a car gas accelerator pedal, that the fan on the PCI was moving from a base of 799 to around 850-900. It's hard to believe such a small jump would kick off this kind of sound but it has been repeated several times. In fact when the PCI fan passes 950rpm the sound seems to decrease with the faster spin. I could be all off here and down an empty path, but I am curious if anyone has any clues as to what might be going on. Or perhaps this is quite ordinary with this higher end card ( I did read that this card could make a lot of noise, but more under load). Other than this, the computer so far is great. I don't want to start with AppleCare or the Apple Store here in Paris if it is doubtful to net me anything. Thanks for any tips or advice.