Ever experienced that uncomfortable ear-thumping sound when you open a car window? Colloquially known as window buffeting or throb, this phenomenon has a scientific explanation called Helmholtz resonance. It occurs when only one vehicle window is lowered, creating a low-frequency throbbing sound, akin to blowing across the top of a bottle.
Neil Lewington, PhD, technical specialist and aerodynamics supervisor at Ford Australia, explains that the principle is similar to producing a hum by blowing across a bottle. The air rushing past an open window creates vortexes that compress and decompress the air inside the vehicle rapidly, resulting in the throbbing sound. This discomforting noise is particularly pronounced in modern cars, which are better sealed and more aerodynamic.
Mark Thompson, PhD, Noise, Vibration, and Harshness engineer at Ford, highlights the effort in designing side mirrors to reduce window throb and the use of a mesh deflector for sunroofs to optimize height and position. Lowering two windows helps alleviate the throb by providing an escape route for the compressed air.
The volume of the sound depends on the speed of air rushing past the opening, making it louder at higher speeds. To avoid window throb, experts suggest driving with only one window open at low speeds, opening two windows at higher speeds, or using air conditioning to maintain comfort.