What causes Line Noise? Line noise has a variety of causes, found inside as well as outside homes and businesses. External Causes - Lightning Strikes: Lightning strikes not only generate damaging surges (voltage increases) but also generate a large quantity of EMI/RFI line noise interference (voltage distortion). Radio & Cell Towers: the air around everyone is filled with a constant stream of radio wave communication, from both radio and cell phone towers. These waves introduce interference into nearby utility power, phone, network and coaxial grids. Internal Causes - Line noise can also be generated within a facility. Lights & Appliances: Fluorescent lights (both the tube and energy-saving, screw-in bulb varieties) generate line noise when it is turned on. Printers and appliances also generate line noise.