If you have a cable box connected to the TV then a ground problem in the cable system can cause a constant buzz that occurs regardless of what source you have the TV playing. Try disconnecting the RF cable from the cable box when you are on a different input. If that works you need a ground lift for the cable line http/www.amazon.com/Viewsonics-VSIS-EU-Cable-Ground-Isolator/dp/B0017I3K9M
If that isn't helpful you may have a ground loop with other causes. Disconnect everything from the TV and see if you get the noise then. If not then this paper on ground loops may help. http/web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
If you get the noise without anything connected to the TV then it is an internal problem of the TV.
If you have a cable box connected to the TV then a ground problem in the cable system can cause a constant buzz that occurs regardless of what source you have the TV playing. Try disconnecting the RF cable from the cable box when you are on a different input. If that works you need a ground lift for the cable line http/www.amazon.com/Viewsonics-VSIS-EU-Cable-Ground-Isolator/dp/B0017I3K9M
If that isn't helpful you may have a ground loop with other causes. Disconnect everything from the TV and see if you get the noise then. If not then this paper on ground loops may help. http/web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
If you get the noise without anything connected to the TV then it is an internal problem of the TV.