The sound reminds me of a phenomenon called "coil whine" present in some graphics cards. Technically, what happens is that a (relatively) high electrical current runs through the inductors, causing them to vibrate. Hence the high-pitched buzz or whine. If this is related, then it's a hardware issue that won't go away with time. I have two identical AMD graphics cards in my computer—one whines more than the other while under load. You need to be down next to it with the case open in order to hear it, but it's definitely there and would drive me bonkers if I had to listen to it all the time.