Here’s why sound travels faster in warm weather but farther in cold weather.

Have you noticed that at night your voice sounds much louder than it is during the day? That awkward moment you keep on hearing a rock concert several miles away deep in the night — and you just can help it. In reality, you’re more likely going to hear sounds better in cold temperatures than it is in warm temperatures. That’s because even though sound travels faster in warm weather, it travels farther in cold weather. Let’s explain.

Related media: What If The Speed Of Light And Sound Were Switched?

Sights And Sounds

Let’s debunk one great misconception about sound. People talk about the speed of sound as if it’s a constant. Spoiler Alert: It isn’t. In fact, the speed of sound changes depending on the environment and what’s causing the sound in the first place. That’s because sound is a pressure wave that’s conveyed by the movement of molecules around — the faster or slower it is, depends on what those molecules are. For instance, sound travels faster through liquids than in gas, and travels faster through solids than in liquids.

Let’s take air for instance, humidity and temperature both play important roles to the speed of sound. The more humid air is, the less dense it becomes — so much for air feeling heavy! — and makes sound travels slightly faster. Check! Heat on a technical note, is the transfer of energy, and thus the movement of molecules. This in turn makes air molecules move around faster, able to carry away a pressure wave faster than slow-moving molecules. Because of that, heat makes sound travel faster, too. Double check!

Bend Down Low

We’re sure you’ve seen how a spoon sitting in a glass of water bends as if it’s broken. That’s because of the refraction of light: light travels in water differently than it does through air. This is the way light rays bend when they move from a medium like air to a medium like water. Technically speaking, the speed of light slows down in water — it takes a bend toward the air-water boundary (try this at home if you doubt us!). This is the same thing that happens to a wave moving through a slow medium to a fast one, it bends away from that boundary, too.

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So what does all this have to do with a winter rock concert? Everything! On that winter cold night, there is a layer of warm air above the cold pockets of the floor. (Why not, it’s a rock concert). As the metal band rock the night, the sound wave that’s suppose to move out in all directions gets refracted by that warm air; and because sound move faster in warm than cooler air, that wave bends away from the warm air and back towards the floor. That makes sound travel farther in cold weather.

The Farther I Go, I’m Heard

You might be wondering, that’s not all that makes winters more quiet. Of course, there’s a lot that’s not happening that makes winter much more subtle than the summer. Snow muffles sound — trapping that wave pressure — thereby all that little buzzes you’d hear are lost reverberating off the ground. Obviously, people stay in doors, so there are fewer cars and activities around enough to make a ruckus. You might be miserable out there in the cold, but at least you have peace and quiet as your reward.

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Written by: Nana Kwadwo, Thu, Jul 11, 2019.


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