why is the speed of sound faster in humid air? I thought it was due to the added moisture making it more dense but I’ve just read that the opposite is true. Can anyone explain?

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If sound travels faster in water due to the increased density and more tightly packed molecules, I would have thought the reason sound travels faster in humid air is due to the added moisture, but I’ve read that humidity leads to a decrease in density and that this is the reason sound travels faster in humid air. The two facts seem at odds with each other. Can anyone explain this?

In: Physics

2 Answers

Anonymous 0 Comments

Water is heavy – or dense – because it is a liquid. Atoms and molecules in liquids are packed close together.

Water in humid air is a gas. Molecules in gasses are much more spread out – and so it is less dense.

A different question is when the air cools and the humidity condenses into fog or cloud – tiny droplets of water suspended in the air. Sound gets badly messed up in fog!

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