What Does Electromagnetic Interference (EMI) Mean?
Electromagnetic interference (EMI) is a phenomenon where one electromagnetic field interferes with another, resulting in the distortion of both fields. This is commonly observed in radios when switching between frequencies and static is heard, as well as on over-the-air TV when the picture becomes distorted because the signal has been distorted.
Electromagnetic interference is also known as radio frequency interference (RFI).
Techopedia Explains Electromagnetic Interference (EMI)
Electromagnetic Interference is a disturbance in the radio frequency spectrum that affects fields even if their frequencies are not aligned. This is because electromagnetic radiation can still interfere with each other even if they are not on the same frequency, and this is exacerbated by the fact that devices emitting electromagnetic waves have a tendency to also transmit at lower power on harmonic side bands, which is why an FM radio might pick up powerful signals from a nearby CB radio.
EMI can be a problem on electronic devices since electronic circuits are very susceptible to EMI because electromagnetic radiation can easily be picked up by any conductor, which is why speakers sometimes make noise when a nearby cell phone is receiving a call or text message. This is because the coil in the speakers is acting like an antenna which captures the EMI emitted by the cell phone.
EMI can be a serious problem in critical systems that use radios such as on an airplane, which is why all electronic devices are required to be turned off during takeoff and landing, as they might cause interference with communication between the pilot and ground control or other critical systems being used by the plane.