How do noise-cancelling headphones block out sound?

Noise-cancelling headphones are like having a friendly helper inside your ears that fights against loud sounds.

Imagine you're at a busy playground, and someone is shouting over you. That’s like the noise around you. Now imagine you have a friend who starts shouting back, but in a way that makes the other person's voice seem softer. That’s what noise-cancelling headphones do!

Sound waves are like ripples in water. When there’s noise, those ripples hit your ears and make you hear things. But inside the headphones, there’s a tiny computer that listens to the sound.

This computer creates its own opposite sound waves, just like when you whisper something secret and someone else whispers back, it makes the secret harder to hear. These opposite waves go into your ears at the same time as the noise. They cancel each other out, like when two ripples meet and make calm water again.

So instead of hearing a loud voice, you might just hear a soft whisper, or even nothing at all!