App note from Coilcraft about electromagnetic interference and its unintention emission and regulation when comes to consumer products. Link here (PDF)
Everyone enjoys the advantages of electronic devices and gadgets becoming smaller, lighter, and faster, while providing longer battery life and ever-improving processing ability. Smaller devices require smaller electronic components an advantage in reducing electromagnetic interference (EMI). However, a compact design also means smaller spacing between components, circuit traces, and enclosures, which can lead to increased field interactions, current loops, ground loops, cross-talk, and other potential sources of EMI.
EMC is verified by testing to industry standards developed by regulating agencies described later in this discussion. These standards define specific test conditions and limits of noise emissions that may vary by location, application, and operating environment.