iMac i5 (Mid-2011) Electrical Noise Occurs when Scrolling or High CPU Usage

I'm getting this weird electrical type noise from my refurb iMac (probably why it's a refurb in the first place).

It sounds like its coming directly from the lower right of the computer. The best I can describe it as is a noise a cricket (insect) makes; it's a soft buzzing/ticking sound that increases in level depending on the CPU usage.

It is heard most often when scrolling up or down a web page with lots of graphics and pictures. It also occurs if I open a large PDF document and scroll up/down. Another example; if I open Aperture and make it full screen and scroll through my pictures the noise will occur. The noise also occurs when the CPU usage goes above 20%.

I have a SSD installed so it definitely isn't the hard drive. It also isn't the fans because I can turn the fans on high/low and the noise sounds exactly the same. It can't be the power supply because that is located in the top left and the noise occurs in the bottom right. I don't believe it's the LCD display either.

Anyone else have/had a similar problem? I'm eventually going to take it into the Genius Bar once I'm totally driven crazy by the noise.

Just noticed today, if I use Mission Control and select another desktop the sound is gone when scrolling but it is still there if the CPU usage goes above 20%.

If I go back to the first desktop the sound is still there either way.

UPDATE: So after about a year living with the noise I decided to take it into an Apple Store and have it checked out before the 1 year warranty ended.

The genius tech was able to hear the noise and decided to replace the entire LCD screen. That however did not solve the issue. What did fix the problem was replacing the logic board itself. Now the noise is completely gone.

I just wanted to update my old thread incase someone else runs into this issue in the future.