What Causes the ‘Sound’ of a Thunderclap and How Is It Measured?

A thunderclap is just air getting really, really hot and then suddenly cooling down, and that makes a big sound.

When lightning strikes, it super-heats the air around it in an instant. This hot air expands very quickly, pushing outwards like a balloon being blown up too fast. Then, when the air cools down again, it contracts, kind of like when you let go of a balloon and it goes whoosh.

This expansion and contraction of air is what causes the loud sound we call thunder.

Scientists use something called a microphone, which is like a really sensitive ear. When the sound waves from thunder hit the microphone, it turns them into signals that can be measured.

They also use distance to help figure out how strong the thunder was. If you’re close to where lightning struck, the thunder sounds louder, just like when you shout in someone’s ear versus shouting across a room.

Sometimes they even use sound level meters, which are like special microphones that tell them exactly how loud the thunder was, measured in units called decibels.