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ELI5 Yahaaa

Air, pushed

How Does Sound Travel?

Sound is not a thing that flies. It is a squeeze passed along from one bit of air to the next.

1 Somethingvibrates2 Air squeezesand spreads3 Your eardrummoves
Nothing flies from the speaker to your ear — the push does.

  1. Step 1 of 5

    Every sound starts with something shaking.

    Vibrating Makes soundHeld still Silence

    A guitar string, a drum skin, your vocal cords, a speaker cone. Stop the shaking and the sound stops instantly.

  2. Step 2 of 5

    The shaking squeezes the air next to it.

    Pushed out Air squeezed togetherPulled back Air spread thin

    As the surface pushes out, it crams the nearby air molecules together. As it pulls back, it leaves them spread thin.

  3. Step 3 of 5

    That squeeze passes itself along.

    The push startshere Arrives hereThe air stays put. The squeeze travels.

    Each crowded patch of air shoves the patch beyond it, which shoves the next. The pattern travels outward while the air itself barely moves at all.

  4. Step 4 of 5

    Your eardrum feels the pushes.

    Your ear A skin being pushed andpulled thousands oftimes a second

    The arriving pattern of squeezes rocks a thin skin inside your ear back and forth. Your brain reads that rocking as sound.

  5. Step 5 of 5

    No air, no sound.

    In air Sound travels at 343m/sIn space No sound at all

    Sound needs something to squeeze. In a vacuum there is nothing to pass the push along, so space is genuinely, completely silent.

    Sound goes over four times faster through water, and about fifteen times faster through steel — the molecules are closer together.

The short version

Sound is a squeeze in the air, handed from molecule to molecule until it reaches your eardrum.

Try it yourself

Press your ear to a table and have someone scratch the far end quietly. It is loud — solid wood passes the squeeze better than air.

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