If you mean the Hum is coming from the built-in speakers of your TV, then you likely have a "ground loop" -- 60Hz power line interference. Check the Hum/Hiss FAQ sticky thread in the Audio Theory forum here for suggestions on how to locate and fix this. HINT: These days the single most common source of such garbage is stuff coming into your house along the cable shield of a cable or satellite TV feed wire. Temporarily disconnect that feed wire where it comes out of your wall. If your hum goes away then you've found the problem. Fix this by correcting how that feed is grounded at the point where it ENTERS your house.
If you mean that there is a buzzing or other sound coming from inside the display -- i.e., *NOT* from its built in speakers -- then you do need to find the proper owner's thread for your model of display in the appropriate displays forum here for your type of display (LCD, Plasma, etc.) as Bill suggested.