Eli5: Why does same sound source get louder if multiplied?

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When I start my boy’s plastic train on a plastic track it has a certain decibel. But when I add many of the same type of train (with same decibel?) on the same track system, I percive the volume to increase, why is that?
I’m not sure it’s the same in a crowd since people tend to raise their voice to be heard when many others are speaking at the same time

In: Physics

2 Answers

Anonymous 0 Comments

Sounds are waves in the air.

How loud something is represents the amplitude of the wave.

When waves overlap they add together.

Think of 2 people in a pool and they both push a wave towards each. When the waves meet in the middle they add together in to one larger wave.

In your example, the waves in the air that the trains are making add together which makes your ear drums vibrate back and forth further which you perceive as louder.

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