High Freq. Noise

[Prospect]

There is a High Pitch sound that comes and goes from the back of my Antec Sonata II case. At first, I thought it was the battery backup/power surge protector that I added but I got a little closer and it was coming from the back of the case. I don't know if it's the power supply that's making the noise or something else but I never had that problem. Could it be that the power supply is failing? Or could it be that it's not getting enough power to it from the battery back up that I recently added? It makes the high pitch sound if the tower is powered on and when it's off, that is why I am very confused. Can somebody please help me with this problem? Thanks for your time.

[Rob]

I would suspect the power supply. There are capacitors in the power supply that can hold a charge for a long time (months, years), so that would explain why the whine would exist when everything is powered off. I don't see how a connection to a UPS or power strip (if I understand right) would make a difference. It wouldn't hurt to try connecting the computer to a wall outlet, but I wouldn't expect it to make any difference.