I'm assuming the sound is coming from the TV's own speakers and not a connected audio system. If this is the case, then return it as soon as you can for a replacement or refund. It's likely defective.
So, I got a Panasonic P50GT50 recently and I am not the happiest with it right now. I went from an old Samsung plasma, which I am now starting to miss to this updated Panasonic plasma. Now, occasionally, this TV has the loudest buzzing sound I have ever heard from a TV. I'm not talking about the continuous hum you normally get, I am talking like almost an annoying alarm clock going off to wake you up. It happens most of all when the TV is changing from commercial to commercial and to program again when the screen is blacked out. I am not talking channel surfing, I mean leave it on one channel and that's it.
I don't know if this is a manufacturer defect or if its normal for Panasonic. All I know is I had my Samsung for 4 years and I NEVER experienced this.
Can someone explain to me what is going on because I thought that Panasonic were suppose to be the best plasma TVs on the market but I am started to think otherwise...