ORLANDO, Fla. – Ever wonder why the highway sounds louder at night, even when traffic seems lighter?
Well, believe it or not, it has to do with the weather.
We decided to break down the elements to show you the impacts.
TEMPERATURE
Temperature plays a big role in how noise is heard. Here’s why.
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During the day, as warm air rises and cool air sinks, sound waves bend upward into the atmosphere and away from our ears so we don’t hear it as much. Once the sun sets and the night air cools, an interesting thing happens —a warm layer of air above the cool night air causes sound waves to bend back toward the Earth. This means that the traffic noise at night sounds louder than during the day, even if there are fewer cars on the road. Sneaky, right?
Oh, and let’s not forget about the speed of sound itself. Did you know that, according to NASA, sound travels at an average speed of 761 mph? But here’s the kicker—the temperature can actually affect how fast sound travels. At lower temperatures, like 32°F, sound slows down to 740 mph, while at higher temperatures, like 96°F, it speeds up to a brisk 788 mph.
Rain can also affect traffic noise as it changes the temperature profile, and of course, we can’t forget the increased noise caused by the vehicle tires driving through the water on the road.
WIND
Now let’s talk about the wind. It’s not just rustling leaves, causing a mess in your yard—it’s also playing a major role in how we perceive sound. The wind can carry sound waves, bending them either toward or away from the Earth in a process called refraction.
When the wind is blowing from the highway toward you (downwind), it amplifies the sound levels, making that rush-hour traffic roar even louder in your ears. But when it’s blowing away from you and toward the highway (upwind), it carries the sound upward into the atmosphere and away from your ears, so the sound levels diminish.
So, there you have it, folks! The next time you find yourself wondering why the highway sounds louder at night, just remember the weather around us is has a big part in what you’re hearing.