The Title more or less says it: Buzzing Sound Behind Flatscreen - Lights Dim Simultaneously. Heard it for first time today. Samsung LCD flatscreen hangs on wall - installed 2 years ago. Home built in '84. Not sure of wiring specifics. When the buzzing occurred a light on the same receptacle as well as lights in an adjacent room all flickered. This happened 2x's in 10 minutes - each lasting 2-3 seconds, tops. How worried should I be? If it recurs should I get an electrician - frankly I am neither knowledgeable or handy with such things.

Those symptoms sound like a brownout or a temporary drop in line voltage. When that happens, your TV will attempt to draw more current. That may be why you hear buzzing.

If the power in your area is not very stable, you might want to do something to protect your expensive flatscreen. Brownouts can cause electronics to overheat.

Several companies produce power line conditioners that protect against brownouts and overvoltage. They range in price from fairly affordable to stupidly expensive. APC, Monster Cable, and Tripp Lite are some brand names to look for.

I should also point out I'm assuming this is an issue with your neighborhood's power supply. If the issue is localized to a specific circuit in your house, then you really should have an electrician look at it. You could have a fire hazard you're not aware of.

Could be a burn't buss that the breaker plugs onto. 1 circuit or half of the circuits? Any loose connection between power source and TV can cause this.

Rereading, I would check receptacle behind flat screen, and that the other end of the cord is all the way in on TV.