Microphones: How They Work

Microphones have gotten quite sophisticated. They can be very small, wireless, and stuck on a lapel pin or they can be handheld wands plugged into a karaoke machine. In most cases they work on the basic principle that like charges repel and opposites attract.

Diagram Explaining How Microphones Work

A microphone begins with a metal diaphragm that bends back and forth when it is struck by sound waves. When it bends in, it is called compression. When it bends out it is called rarefaction. The metal diaphragm is negatively charged from the battery (or power source), while the fixed plate (situated close to the diaphragm) is positively charged. When the sound wave creates compression, electrons jump from the diaphragm to the fixed plate. This causes a positive signal to be sent from the microphone.

When there is no sound, the diaphragm is flat. At this point its negatively charge exactly balances the positive charge of the fixed plate. When rarefaction (not really a rare occurance) takes place, the negatively charged metal diaphragm moves away from the fixed plate. Then the negative electrons in the diaphragm repel each other and the flow out of the diaphragm, causing an opposite flow of electrons from the flow that occurs in compression.

These signals are exactly in phase and amplitude to the sound waves hitting the diaphragm. They are usually sent to an amplifier for further processing.

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