Electromagnetic Interference is defined as any conducted, radiated, or magnetically induced voltage which degrades, obstructs, or repeatedly interrupts the desired performance of electronics equipment. There are four fundamental interference sources:

• Man-made noise
• Electrostatic Discharge
• Electromagnetic pulses through nuclear reactions (NEMP, EMP)
• Cosmic noise – sometimes referred to as audio hum, crosstalk, degenerative feedback, electrical noise and RFI (radio frequency interference)