I've had this TV about 5 years, admittedly it's not top of line, but it works, or used to work. I get picture and sound and the buzzing started out of the blue about a month ago. It's been plugged in to the same outlet all those years, the only thing I added was a dvd player about a year ago. (No techie here.) The buzzing started out loud and then got softer, then last weekend it started going on softer then just got louder and louder. The level, once it settles down, is the same whether sound is up or down. I have unplugged and replugged, disconnected the dvd, taken all plugs from that socket except TV. I think it's getting worse. Do I need a new TV?
Sounds like you need a new set. Somethings going out inside of it. I would say its a ground loop issue, but since you arent seeing any hum bars in the image, I tend to think its something else. Just to be sure though, try plugging the TV into a different outlet via an extension cord and power strip. If the problem persists, chances are you just need a new set.