You are out enjoying a nice drive. The weather is nice enough to warrant putting down the windows. Then you are met with a loud helicopter-like thumping inside the car while driving. So, what is that annoying noise, and why is it happening more often with newer cars?
According to Erie Insurance, what you are experiencing as you roll down your car window on the highway is called wind buffeting.
Wind buffeting is caused by what’s called Helmholtz Resonance. According to Car and Driver, this is the same phenomenon that makes a glass bottle hum when you blow over the open top. It occurs when the air in a container with one opening interacts with the air that passes over that opening. In the case of a car, the car is the container, and the window is the opening. The air inside the vehicle thumps up against the air flying outside the window.
When these two masses of air clash, they then compress and decompress over and over again. This causes small wind vortexes, and those cause the annoyingly loud thumping and throbbing noise.
There are a few factors that can affect your wind buffeting experience. More aerodynamic cars have louder thumping than older and boxier models. Your car’s speed affects buffeting as well. The faster you move, the louder the buffeting will be to you. Finally, wind buffeting is worse when the back windows are open. Front windows have side mirrors that help deflect the air and reduce buffeting. Side mirrors are placed and explicitly designed for redirecting airflow to minimize airflow by the front windows.
According to Family Handyman, wind buffeting is worse in newer cars. Why? It’s because newer cars are more aerodynamic. The shape and design of these vehicles help them move through the air much more effortlessly, reducing drag. This means that the wind can pass over in a very efficient manner.
On the other hand, older vehicles were much boxier and less efficient. Air leaks into the cars all the time. That leaking air would relieve the pressure caused by wind buffeting. Newer vehicles are designed to keep the air inside rather than escaping or entering. Keeping air from going in or out of the vehicle helps improve fuel economy among other things.
When you open a window, all the air that was closely hugging the vehicle is disrupted. That disruption in the smoother airflow causes the annoyingly loud thumping in your ears.
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All you have to do to stop wind buffeting is to open another window. The buffeting occurs when you open one window and disrupt the airflow. Opening a second window stabilizes the pressure inside the vehicle. Evening the pressure allows the buffeting to stop together or at least minimize it.
There are also cars with deflectors on the front edge of the side windows. These deflectors help direct the air out and away from your car. Your sunroof or moonroof may already have a deflector as well.
So, if you love a good drive with your window down, look for a car with deflectors to reduce wind buffeting. Also, watch out for aftermarket roof racks. Roof racks can contribute to buffeting thanks to reducing the aerodynamics of your vehicle.
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