Why do I hear extra noise when using 2 monitors w/460 graphics card?

I am wondering if anyone can help me out with this strange and puzzling problem that I am experiencing.

I am using a a single Gigabyte GV-N460OC-1GI (GeForce 460) card
GIGABYTE - Graphics Card - NVIDIA - PCI Express Solution - GeForce 400 Series - GV-N460OC-1GI

into which I have a couple of Samsung P2450H monitors connected via the DVI cables:
24" LCD Monitor | Samsung Office

My motherboard is a ASUS P6X58D Premium, my case is a HAF-X, I am not overclocking my i7-950 and my CPU cooler is a Cooler Master Hyper 212+.
So here is what I am expereincing. 90% of the time when I have BOTH of the monitors turned on, I hear a very faint high-frequency noise emulating. If I have only one of the monitors turned on (doesn't matter which one), there is no noise. This "extra" noise is coming from somwhere within the case, so it could be the motherboard or the graphics card or ???. I very much doubt that it is any of the fans, as those are nearly silent and I would easily notice this by seeing "faster" RPM speed when I run Everest Sensor program. Also, I have double checked that Windows 7 display is setup for 60Hz for both of the monitors. My system is only 3 weeks old, and I doubt it's a capacitor issue (?!?)

This noise is barely audible, but I definately hear it (I am a professional musician...). The noise is very different that the one people used to get when we all had CRT monitors and were trying to run in the "wrong" resultion. That was a very clear high frequency pitch that almost everyone could hear.

Does anyone have any ideas what could be happening?

I'm unsure whether this is a red herring, but could you experiment with the refresh rates for the graphics card and see if that noise persists?

Golden said:

I'm unsure whether this is a red herring, but could you experiment with the refresh rates for the graphics card and see if that noise persists?

That would make sense but both work fine without noise if they are individually (one on and one off). I would think that if there was a refresh issue, it would come out individually also.

Golden said:

Mmmm.....its the only thing I can think of. Its not a loose mechanical connection, and the fans don't spin up any faster either.....Can you humour me and try it anyway, if you haven't already?

Oh, one other thing : can you tell me about your PSU please?

The other possibility is that as the the card works harder,the choke coils are warming up causing some vibration.....I have heard of people fixing this by dabbing glue or nail varnish on the coils to dampen the vibration, but I've never done that myself......

Perhaps some experts here could offer advice.

Thanks and appreciate ALL suggestions! My PSU is a good one, Silencer 910:
Silencer 910

Actually, I don't think Everest shows me the FAN speed of the GPU (graphics card). Is there a program that would show me the speed of the two fans on my graphics card? I doubt it is causing it but I really want to rule-out everything.

Last point: I double checked in my Device Manager that both of the monitors are running at 60Hz (exactly for LCD) and the drivers are specific for my Samsung model. They are show as: SyncMaster P2450H(Digital). I tried to update the driver, but it told me that I am already currently using the latest ones.

You could try Speedfan.

Golden said:

You could try Speedfan.

I finally tried the Afterburner utility (on a recommendation), and I can tell you that the "noise" has nothing to do with the fans. Of course when I jack them up to100%, I hear a very clear "woosh" sound. But even bringing down the fans to "30%" does not make the higher-frequency sound go away. I have been told that the choke coils could be creating this issue.