Every driver and passenger has experienced the infuriating rush of noise as they open their window on the motorway, but there’s a simple way to fix it. The noise is caused by Helmholtz Resonance, the same concept as when you blow across the top of an empty bottle. Air passing over the top of a small opening in a vessel (your car window) creates mini vortexes which spin around the cabin as waves of pressure causing your ears to interpret them as sound. To reduce the intensity just open another window, or all four to really tone it down. The phenomenon is worse in modern cars because improved aerodynamics means the wind passes closer to the car, whipping through the window at a higher speed. The problem is more noticeable if you open just the rear windows as your wing mirrors push the air out slightly, disrupting its flow across the car, before it shoots back in through the back windows. So, the next time you wind down your window to enjoy the breeze, open the other three.