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How a Microphone Works

You’re playing an online game with your friends when your boss calls you. “Be right back!” you tell them. You answer the call and greet your boss, who tells you that you’re needed at work tomorrow. You hang up and curse under your breath, but your friends heard you.

All communication in the above scenario has been sponsored by the microphone! Yes, folks, the device that’s been bringing you someone else’s voice for 140 years is still here, and better than ever! Modern microphones are a technological wonder, capturing sound waves and sending them thousands of miles away. How do they do it? To understand this, we first need to understand sound waves. Your voice – or any sound for that matter – is a standing wave that is set up using the air particles around you. Your vocal folds create subtle but powerful pressure changes in the air in your throat, and these pressure changes propogate out in to the world around you. Inside of your microphone, there is a small membrane of metal, plastic, paper, etc. known as the diaphragm. As the pressure in the air changes, the diaphragm moves back and forth with the air particles. Attached to the diaphragm is a small magnet, which is pushed in and out of a coil of wire. The moving magnet causes changes in the magnetic field around the coil, which induces a current. Different volumes, pitches, and types of noises will vary the current that is induced, which is how a microphone can pick up such a wide variety of sounds. The generated current is translated into digital binary by either a small built in processor (in the case of a USB microphone) or some hardware implementation like a soundboard. The digital content is then sent across the country to your friends, or down the road to your boss.

It’s pretty amazing how something so common in our everyday lives can take some air particles that were wiggling around in your throat, turn them into ones and zeros, and send them wherever you want. Thank you, electrophysics!

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