Windtunnel Measurements of Aerodynamic Noise Sources of Full Scale Motor Cars

Tests in two large windtunnels designed for investigations on car aerodynamics have been carried out to determine the dominant sources of wind noise of full scale automobiles by means of the acoustic mirror telescope. The principle and characteristic features of this device are discribed. Measurements of the acoustic source distributions along the sides of the cars demonstrate the potential of the acoustic mirror system to identify dominant sources of aerodynamic noise, to measure the distribution of noise source intensity and to investigate the effect of modifications to reduce the noise radiation. The latter feature is particularly important if there are several noise sources of similar intensity.