We have just started using our new Dell Precision 5720 AIO and noticed that when the room is completely quiet, there is a humming noise coming from the lower, center of the screen. The noise will change in pitch (frequency) when I adjust the screen brightness and will go away if i leave the screen brightness set to 100%. Noise also gone when the screen turns off and the AIO is still on. Is this normal operation? Do other users hear this noise? Is there a problem with my screen power supply (maybe the backlight driver or power supply in general)? Is there a problem with my AIO? Thank you for any feedback you can provide before I start talking to Dell.