Q- Why do speakers or headphones make a buzzing sound when a mobile phone is near them?
Answer:
Many speakers, headphones and other electronic gadgets may produce a distorted or buzzing sound when a mobile phone is near them because of electromagnetic interference. Almost every electrically powered equipment acts as a radio transmitter, whether it is supposed to or not. That's because the rapidly changing electric currents running through these devices naturally radiate electromagnetic waves. The signals that are going to the speaker are electromagnetic and they are of a particular frequency. Mobile phones also receive the same signals but of a different frequency. Whenever these signals meet , they disrupt and the final electromagnetic waves reaching the speaker is of a higher amplitude causing distorted noises.
Even computers emit radio waves in the range of frequencies reserved for cell phone communications, typically around 800 megahertz (MHz). If the signal coming from the computer is strong enough, the mobile phone can mistake it for a cell phone transmission, resulting in a distorted noise. If the mobile or speakers are not electromagnetically shielded there chances of such occurrences.
A mobile phone has an audio amplifier that drives its speaker and the radio waves emitted by the speakers may induce currents in the wiring of the amplifier itself.