Just went and got a 55inch proscan TV, came home and hooked it up and my Xbox was making a high pitched ringing noise all of a sudden. When off it stops. But my room mate texted me today and said that the TV is making a slight ringing noise too. Any ideas as to what it might be, or if there is any way to get rid of it.
You may have a ground loop or a bad TV.
Disconnect the TV from everything except the AC.
If it is making that noise it is defective. Return it.
If it is not making that noise then reconnect your external connections one at a time. When the noise comes back you will need to try a ground lifter on the AC cord of that source.
You might want to try to get the TV exchanged in either case. It should not have this issue.