Faint buzzing from a TV is normal when it is turned on. If it is a plasma TV, the buzzing noise could be due to the altitude of the television. If a plasma TV is above 6,500 feet, it may buzz loudly.
Buzzing can occur if a second high-powered appliance is in use, which can cause electrical feedback. If the buzzing noise continues 10 to 15 feet away from the TV, make sure there are no cables resting against the back panel. If the noise still continues, unplug the TV and other entertainment components for 30 seconds. Plug only the TV back in. The TV is working normally if the buzzing has stopped. If it continues, try adjusting the light values.