My Panasonic P50U50 is making a buzzing noise. It changes depending on what's being displayed, when it's just displaying black, it makes less buzzing noises (it sounds like there's one thing buzzing instead of 2, or something like that). It seems to be coming from the top of the TV, and turning off the integrated speakers doesn't do anything about the noise. It's been doing this since I got it, but I hadn't really thought much of it until now. Is this normal, or do I need to get it fixed?