Variation of Pure Tone Sound Amplitude Caused by Non-Uniform Acoustic Field Deviation in Automobile Wind Tunnel

Abstract:

From the perspective of non-uniform sound field offset， the mechanism of pure-tone sound-amplitude large change with wind speed which measured outside flow field of automobile wind tunnel was studied. A wind tunnel test was conducted with a controllable sound source on the automobile surface as the research object. The amplitude fluctuation of pure tone sound pressure level at different wind speeds was obtained by microphone， and the non-uniform distribution of sound field was observed by microphone array. Based on the point source interference theory， the non-uniform sound field was simulated and reconstructed， and the influence of each reflecting wall was analyzed parametrically. The acoustic field offset caused by shear layer refraction was deduced according to the geometrical acoustic theory， and the trend of pure tone amplitude variation at different test wind speed was predicted. The results show that the deviation of the non-uniform sound field caused by the interference is the fundamental reason for the amplitude fluctuation of the pure sound in the wind tunnel， and the reconstruction method of acoustic field can effectively reduce the error.

Key words:vehicle engineering;wind tunnel;sound amplitude;acoustic interference;acoustic field deviation