Hardware · Cabling
Electrical Noise
Also known as: Electrical Interference, Signal Noise, Electromagnetic Noise
Electrical noise is unwanted electrical signal interference that degrades data transmission or power quality — caused by motors, fluorescent lights, power lines, and other electrical equipment running near signal cables.
Every electrical conductor carrying alternating current radiates an electromagnetic field, and every conductor in that field picks up an induced voltage. When that induced voltage is high enough relative to the signal being carried, it becomes noise — corrupting data signals, triggering false alarms in control systems, or reducing power quality.
Common noise sources in IT environments:
Power cables running parallel to data cables — a power cable carrying 60Hz AC induces that frequency onto adjacent data cables. The NEC requires minimum separation distances for this reason.
Fluorescent and LED driver ballasts — switching power supplies in lighting fixtures generate high-frequency noise.
Motors and HVAC equipment — variable speed drives, compressors, and elevators generate broadband electrical noise.
Switching power supplies — all modern computer power supplies are switching-mode, generating noise at their switching frequency (typically 100kHz-1MHz) and harmonics.
Copper data cables are susceptible to electrical noise. Shielded twisted pair (STP/FTP) cable adds a foil or braid shield that contains noise and reduces susceptibility, but requires proper grounding to be effective. Fiber optic cable is completely immune to electrical noise — one of its primary advantages in electrically noisy environments.