Why is cumulative sound louder?

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This is definitely stupid, think I’m missing something.

If I say something at 60 decibels for example, the person I’m talking to will hear it at that volume (ignoring the sound lost over distance).

But if a crowd of people say something at 60 decibels, it will be louder to the person hearing it.

I just can’t get my head around why, since they’re all talking at the same volume as the single person. What amplifies it?

In: Physics

7 Answers

Anonymous 0 Comments

Sound is a wave, more fundamentally (zoom in closer) sound is pressure wave of (for example) air molecule density compressing (getting squeezed together) and air molecule density expanding (spreading out).

You often see waves illustrated as transverse waves like strings (sine wave). But sound is longitudal wave, like pushing a slinky.

Back to the air molecules. Perhaps think of them as grains of rice on the table that are bunched up on regular intervals and less dense regions between them.
So if one voice can bunch up 100X air molecules together as the wave progresses. Another voice that does the exact same you now have doubled density. Note the is not creating the air molecules or making wind to push them from somewhere. They are just locally compressing/expanding as a wave.

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