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ELI5 Yahaaa

How big the push is

What Makes a Sound Loud?

Loudness is not about speed of vibration. It is about how far the air gets shoved.

Quiet Small pushes — airbarely movesLoud Big pushes — air shovedhard
Same note, different amount of shove.

  1. Step 1 of 5

    Loudness and pitch are different things.

    Pitch How often the pushrepeatsLoudness How big each push is

    Pitch is how often the air is pushed. Loudness is how hard. You can play the same note quietly or deafeningly.

  2. Step 2 of 5

    A bigger vibration shoves more air.

    1 Hit harder2 Skin swingsfurther3 Bigger pressurechange

    Hit a drum harder and the skin swings further. It crams the air more tightly on each push, so a stronger pressure wave leaves.

  3. Step 3 of 5

    Your eardrum moves further.

    Your eardrum Pushed further with alouder sound

    A big pressure swing pushes your eardrum further in and out. More movement means a stronger nerve signal and a louder experience.

  4. Step 4 of 5

    Loudness fades fast with distance.

    At 1 metrefull loudnessAt 2 metresa quarterAt 4 metresa sixteenth

    Sound spreads over an expanding sphere. Double your distance and the energy spreads over four times the area, so it drops to a quarter.

  5. Step 5 of 5

    Decibels are a squashed scale.

    Jet engine — 130 dBinstant damageTraffic — 80 dBsafe for a whileWhisper — 30 dBbarely there

    Our ears handle a colossal range, so we count in decibels. Every 10 dB is ten times the energy — 90 dB is not slightly worse than 80, it is ten times worse.

    Sustained sound over about 85 dB damages hearing permanently — and the damaged cells never grow back.

The short version

Loudness is how hard the air gets pushed; pitch is how often. They are independent.

Try it yourself

Pluck a guitar string gently and then hard. Same note both times — only the size of the wobble changed.

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