Hi, I am asking this question because I am on my 4th replacement and all my iMacs have had this issue (among others). This last replacement is actually the best one I have recieved, as it only has this problem and some gray banding. This has been my experience so far: 1st - Yellow tint, high pitched noise (when lowering brightness), 1 dead pixel. 2nd - Yellow tint, high pitched noise, 1 dead pixel (like the 1st one!) 3rd - Minor Gray banding, high pitched noise, 2 dead pixels. 4th (and current one) - Gray banding, high pitched noise. I can see how unlucky I am. On the other hand, I have a friend who recently bought a 27" and also has the high pitched noise. He says he can live with it, as he's always on 100% brightness. The thing is, are there really imacs without this issue? To all the people saying that they have a 100% perfect unit, have you tested THIS? I am aware that as people age, they stop hearing high pitched sounds (high frequency). Maybe the people that say they can't hear it it's because they are uncapable to do so? I'm 21 years old and have heard it in all my imacs. Please I would like some advice, as I'm starting to get tired of this. Thank you!