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What is sound?

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Quick answer

Sound is a form of energy that travels as vibrations through a medium like air, water, or solids. When something vibrates, it pushes the particles around it back and forth, creating waves that your ears detect and your brain interprets as sound.

Key things to understand

  1. Sound is a vibration that travels as a wave through a medium — it can't travel through a vacuum (empty space).
  2. It needs particles to pass through: it moves fastest in solids, slower in liquids, and slowest in gases like air.
  3. Pitch depends on frequency (how fast the vibration is); loudness depends on amplitude (how big the vibration is).
  4. In air at room temperature, sound travels about 343 metres per second.
  5. Your ears turn these vibrations into nerve signals the brain understands as sound.

People also ask

Can sound travel in space?
No. Space is a near-vacuum with almost no particles to vibrate, so sound has nothing to travel through. That's why space is silent.
What's the difference between pitch and loudness?
Pitch is how high or low a sound is, set by the wave's frequency; loudness is how strong it is, set by the wave's amplitude.
Why does sound travel faster in water than air?
Particles are packed closer in denser media, so vibrations pass from one to the next more quickly — sound moves several times faster in water than in air.