Long(~ish) time reader, first time posting and all that (hi!)
I bought 2 U2412M's a few months back and they both, though the other is far less noticeable, give off a high pitched sound when not at 100% brightness, though the sound can only really be heard when placing my ear close to the upside of the monitor and even then the sound seems to be very directional, meaning that if I move my head by just a centimeter to the side I can't hear it anymore. There are 5-6 spots like this along the upper rim.
At the spot where I'm sitting, around a meter away I can't hear it, though sadly my current computer is not as silent as I would like it to be (about to change soon, I hope), not to mention me having slight tinnitus...
Worth noting that the monitors have markings that say 'U2412Mb', in which the 'b', according to http://en.community.dell.com/support-fo ... 52392.aspx
, means that the manufacturer location is different from U2412M's.
Also, it says that they're Rev. A00, though I'd figure it means that it's the first revision of the U2412Mb batch, rather than having anything to do with the U2412M Rev. A00, which I remember reading was not the best version of the original monitor around.
Also, the same high pitched sound at greater volume is produced when displaying a clock and phase test picture such as http://www.lagom.nl/lcd-test/clock_phase.php
When displaying that picture, the high pitched sound can be heard at the 1 meter distance I'm sitting at and can also be heard at full brightness.