I've had the plasma TV since Dec of 2006 and all of a sudden I would hear a strange sound coming from the back of the TV. It happens when the tv is on for about 10 mins then that strange sound would come and go. And also the same sound happens after I turn off the TV. I tried calling Panasonic but since the warranty is up they were no help so they gave me some numbers to a tv repair shop and they charging alot of money just to come and look at the problem. Has anybody experienced this before?