What is sound?
Sound is something shaking. Feel it in your throat, see it make rice jump, and find out why space is silent.
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Put your fingers on your throat and hum. Can you feel it buzzing? That buzzing is a vibration: something shaking very fast. Every sound starts with something that shakes.[1]
When something shakes, it pushes the air next to it. That air pushes the next bit of air, and so on, all the way to your ear. Inside your ear the eardrum starts to shake too, and you hear the sound![1]
Some sounds are loud, like thunder, and some are quiet, like a whisper. Very loud sounds can hurt your ears, so cover your ears or move away when something is too loud.[3]
In space there is no air. With nothing to carry the shaking, sound cannot travel. Space is silent![5]
Long ago, in 1883, a volcano called Krakatoa exploded. It was so loud that people heard it on an island about 4,800 km away![4]
Try it: Jumping rice
You need
- A bowl
- Cling film (plastic wrap)
- A few grains of uncooked rice
- A metal pan and a wooden spoon
Safety
Bang gently near faces and ears. Don't eat the rice afterwards.
What to do
- Stretch the cling film tightly over the bowl, like a drum.
- Put a few grains of rice on top.
- Hold the pan close to the bowl, but not touching it, and bang it with the spoon.
- Watch the rice. Now try banging softly and then harder. What changes?
What happens, and why?
Banging the pan makes it shake. The shaking pushes the air, and the air makes the cling film shake too, so the rice jumps. A harder bang makes bigger shakes, a louder sound and higher jumps.[1]
Play: Loud or quiet?
A sound appears. Is it loud or quiet? Tap the right group.
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 10–11 · Ages 15–16