Does the noise come from the speakers, or from inside the box with the volume turned all the way down also?
You might try a noise reducing surge protector power strip (glorified extension cord) to plug the computer and television into.
You might try improving the grounding. Get a long (bare or insulated, #14 to #18 gauge) wire and daisy chain it from one piece of equipment to the next. For the computer, attach it to one of the screws that holds the back cover in place. For the television, attach it to one of the stud jacks in back for left/right audio or composite video (yellow). Connect the far end of the wire to a known ground. For the latter you might get away with a radiator or a water pipe or the screw that holds a receptacle cover plate on but a sure shot is down the basement stairs to the electrical panel or the fat bare ground wire coming out of that.
Note that plug in noise reducers (that "clean up" "dirty" power) draw some power 24/7 unless unplugged. The harmonics that get filtered out are dissipated in a manner not too different from running a light bulb or heater and that counts as billable power.
You might try a noise reducing surge protector power strip (glorified extension cord) to plug the computer and television into.
You might try improving the grounding. Get a long (bare or insulated, #14 to #18 gauge) wire and daisy chain it from one piece of equipment to the next. For the computer, attach it to one of the screws that holds the back cover in place. For the television, attach it to one of the stud jacks in back for left/right audio or composite video (yellow). Connect the far end of the wire to a known ground. For the latter you might get away with a radiator or a water pipe or the screw that holds a receptacle cover plate on but a sure shot is down the basement stairs to the electrical panel or the fat bare ground wire coming out of that.
Note that plug in noise reducers (that "clean up" "dirty" power) draw some power 24/7 unless unplugged. The harmonics that get filtered out are dissipated in a manner not too different from running a light bulb or heater and that counts as billable power.