The best way to figure it out is to try different inputs, Does it happen on the cable RF port only or does it do it on the AV inputs also, if it does it on the AV inputs then it is likely the tv. If it only does it on the rf port than ot could be the source of the RF. If you have a cable box with AV outputs see if it does it there. you could also try using a regular off air antenna to see if it comes in that way. Basiclly what I am saying is that the problem is more than likely a cable company problem and it is called 60hz hum. it doesent sound too severe so the cable co. hasn't put time into it to track it down, you are probably the only one to call. If you Live in an apartment complex or at the end of line it may be like that until the cable company's amplifier actually fails, it is probably the one closest to your place.