Why Does Driving With a Car’s Rear Windows Down Hurt Your Ears?

One moment you’re cruising along the road, and the next, you’re faced with an ear-throbbing sound. It’s happened to most of us at some point—and it’s all because someone in the back seat decided to crack a window. Here’s why.

1. The Science Behind the Ear Pain
2. How to Stop the Ear Pain

The Science Behind the Ear Pain

This unpleasant sensation is all due to some chaotic physics known as Helmholtz resonance, which makes your car into somewhat of a musical instrument when the conditions are just right. 

When you roll down one rear window while driving, the car essentially turns into a massive version of an empty soda bottle. Blow across the top of that bottle, and it’ll make a note. That’s because air rushes across the opening, gets sucked in, and then springs back out again. This creates a loop of vibrating air.

The exact same thing that happens when you crack your car’s rear window. Air gets pulled in through the back window, compresses the air inside the car, and then springs back out, over and over again. That pulsating movement creates pressure waves that slap against your eardrums.

Except instead of a cute little whistle like you’d get by blowing on a soda bottle, the frequency is so low that it becomes infrasound, a.k.a. a sound that is below the lower range of human hearing. You might not hear it, but your ears can feel it.

The effect is so intense it can hit pressure peaks around 130 decibels—for context, that’s louder than a jackhammer or a rock concert.

How to Stop the Ear Pain

Oddly enough, rolling down the front windows doesn’t do the same thing. That’s because the airflow up front is messier, and the resonance breaks up before it even starts.

The shape of your car matters, too. Today’s vehicles are way more aerodynamic and airtight than their boxy, leaky ancestors. That’s great for fuel efficiency, but it makes it much harder for air to escape. When you open just one rear window, there’s nowhere for that compressed air to go … except straight into your ears.

Opening more than one window (ideally the one across from the one that’s been rolled down) is how you can prevent this jarring feeling. You could also opt to keep your back windows entirely closed and crack open the front ones. Or, if you want to avoid any potential disturbances, you can simply just crank up the air conditioning. 

Read More About Cars: