Viewing data for Noisy Screen

Comments: just received my new iMac 21.5" and it also has this very annoying high pitched whistle (like old CRT TVs).
Serial W8949, hence made in Shanghai in week 49, if I'm not wrong.

Differently from what others have experienced, changing brightness from min to max doesn't affect noise volume nor frequency.

Since everyone here has a slightly different problem (and we all have different ears, which makes things even more difficult to compare) I have done a few experiments, and noticed that:

1. At boot up, noise shows up briefly then disappears (simultaneous to and same duration of the "Apple chord").

2. Once booted, the machine is silent, but any of the following actions trigger the noise:
remove one icon from the dock (starts when releasing the mouse button)
play a song from a CD (starts when pressing play on iTunes)
play a video from DVD (starts when pressing play on DVD Player))
play a song from file (starts when clicking on the file)
taking a picture from PhotoBooth (starts when pressing the shutter button)
... and probably many others ...

3. In all above cases, noise stops by itself after about 30" (or by putting the machine to sleep) which makes me think it might be a matter of fans (CPU/GPU), but this is only a guess, I'm not an electronic technician.

Tomorrow I'm going to try to have my iMac replaced at an Apple Store, but only if they allow me to check the new one on the spot, because having another one sent from abroad seems to me too risky, having heard (in this thread only!) people experiencing problems like yellowish screens, dead pixels and of course noise, even after multiple replacements.

Specs: 21.5" 3.06 Core2Duo 500GB

Source of comments: PaoloS

Serial Number: W8949

Date Ordered:

Date Shipped:

Date Arrived: 2009-12-10

Destination: Italy

Courier: Fedex