Automobile Wind Noise Speed Scaling Characteristics

Wind noise, an aeroacoustic phenomenon, is an important attribute that influences customer sensation of interior quietness in a moving vehicle. As a vehicle travels faster, occupants' sensation of wind noise becomes increasingly objectionable. The purpose of this work is to investigate the increase of wind noise level perceived by a driver in response to an increase in wind speed. Specifically, it explores how much the level of wind noise at the DOE (driver outboard ear) would vary in response to a change in wind speed based on the test data obtained in a wind tunnel from ten vehicles that belong to several different passenger vehicle segments. The first part of this work studies the change of the SPL (sound pressure level) in response to a change in wind speed U. It shows that the SPL(dBA) approximately scales to U^5.7 at the DOE and to U^6.3 in the far-field, which could be interpreted as the dominance of dipoles. The second part of this work looks into the scaling of loudness measured in Zwicker sones that represent the human auditory sensation of wind noise level. It shows that the human perception of the wind noise loudness scales to U^1.7 approximately, which indicates that the wind noise loudness sensation is doubled when the vehicle speed incurs a 50% increase.