My 50" Samsung Plasma is humming/buzzing too, and it is very audible throughout the room, even 12 feet away. My normal seating position is 6-8 feet away, but you can hear the buzz from anywhere in the room. It gets worse with bright images, even in bluescreen. I HATE THIS BUZZING.
I tried a variety of things to see if any other device is causing it. Normally, all my AV devices go through my PureAV console, and none besides my Plasma are having this issue. Nonetheless, I tried unplugged everything else in the room, changed plugs, etc. But nothing seems to help. Plugging directly into various outlets in the room, or going through the PureAV console makes no difference.
I have another TV, a 46" Vizio LCD panel, and it doesn't make any buzzing noise, I even moved it into the same room and plugged into the same outlet as my Samsung just to see if it gets the same symptoms, but it didn't.
I've read in multiple forums and multiple online sources that this buzzing is very common with all brands of plasmas; pioneer, pannasonic, etc. I haven't yet read any solutions despire hours of reading across the internet. I am nearly at the breaking point, and ready to banish plasma from my house, and switch to LCD. I can't believe this is such a widespread problem and there is no solution to it. As good as plasma picture quality is, it is completely unbearable, if the manufacturers can't overcome this problem then plasma is dead to me.
Someone please tell me you have found a way to overcome this problem.