Side window buffeting: a smartphone investigation on a car trip

Abstract

Movement of air over a hole or cavity typically generates sound, which can have both noisy and tonal components (cavity noise, cavity tones). Such acoustic phenomena often tend to be a nuisance, e.g. for ‘buffeting’ or ‘wind throbbing’ noise, where airflow over an open side window or sunroof in a moving vehicle can produce low-frequency, high-amplitude ‘booming’ sound signals. The present contribution provides a first description of this curious phenomenon of everyday physics at an intermediate difficulty level, comparing a simplified theoretical model based on a Helmholtz resonator with experimental data obtained by everyday mobile IT devices—namely smartphones or tablet PC. Readers thus are able to reproduce and study the buffeting frequency of a car interior, based on relatively inexpensive equipment using their own mobile devices for data acquisition and analysis.