# How a Microphone Works

How a microphone turns sound waves into an electrical signal, following a ringing tuning fork through the grille, diaphragm and magnet coil\.

By sunny\-koala\-10215ae1

Topic: Art, Music & Film

[Open the interactive Jig](https://ask.jig.com/j/T9WsqqjKZxMd)

## Transcript

### 1. Sound into electricity

A microphone turns sound into a tiny electrical copy that can travel down a wire\. Here a tuning fork is ringing next to a microphone on a studio desk\. Let's open the microphone up and follow the sound inside\.

Drag anywhere to turn the scene and look around\.

### 2. Sound is moving air

The ringing fork's prongs push and pull on the air\. The air bunches up, then spreads out, in waves that race outward at about 343 metres per second\. Try a low note and a high note\.

The dots are slowed down a lot\. A real A note shakes the air 440 times every second\.

### 3. In through the grille

The round metal mesh at the front is the grille\. It lets sound waves in but keeps out fingers and spit\. Behind it, a layer of foam softens the puffs of breath from sounds like p and b\.

On this kind of microphone the grille ball is about 5 centimetres across\.

### 4. The diaphragm

Let's cut the microphone open\. Just behind the foam sits the diaphragm, a very thin, light plastic dome\. Each push of air nudges it in and each gap lets it spring back, so it trembles in step with the sound\.

The real movement is tiny, often less than the width of a hair\. Here it is made much bigger\.

### 5. Coil and magnet

Glued to the back of the diaphragm is a coil of very thin copper wire, wrapped around a strong magnet\. When a wire moves near a magnet, electricity flows in it\. Strike the fork and watch the coil\.

This is called electromagnetic induction\. A power station generator uses the same idea\.

### 6. An electrical copy

As the coil slides in and out, the electricity flows one way, then the other\. Two wires carry this wavy signal out through the handle\. On the screen, its shape is a copy of the sound wave's shape\.

The signal is tiny, about 1\.6 thousandths of a volt for a loud voice up close, so an amplifier makes it bigger\.

### 7. Loud and soft

A louder sound pushes harder on the diaphragm, so it swings farther and the electrical wave grows taller\. A soft sound makes a small wave\. Slide to change how loud the fork rings\.

### 8. The same idea in reverse

A loudspeaker works the other way round: electricity moves a coil, and the coil pushes a cone that makes sound\. Some microphones use a charged plate instead of a coil\. But every microphone starts with a thin diaphragm dancing to the air\.

Microphones with a charged plate are called condenser microphones\. They need a little power to work\.