Wind-Tunnel and On-Road Wind Noise: Comparison and Replication

A KIA Soul was instrumented to measure the relative velocity (magnitude and yaw angle) at the front of the vehicle and in-cabin sound at a location close to the side glass near the A-pillar vortex impingement. Tests were conducted at a proving ground under a range of conditions from low wind conditions (~3 m/s) to moderate (7-8 m/s) wind speeds. For any given set of atmospheric conditions the velocity and sound data at any given position on the proving ground were noted to be very repeatable, indicating that the local wakes dominated the "turbulent" velocity field.

Testing was also conducted in an aeroacoustic wind tunnel in smooth flow and with a number of novel turbulence generating methods. The resulting sounds were analyzed to study the modulation at frequencies likely to result in fluctuation strength type noise. The wind-tunnel results were compared to the on-road measurements to investigate the potential of generating repeatable and controllable turbulence in a wind tunnel which replicates the modulated noise experienced on-road.

The results showed that the novel methods used do increase the modulation significantly and subjective analysis indicates that the modulation generated was similar to that experienced on-road. Analytical analysis of the same data showed the extent of the modulation and it was found that that the magnitude of the modulation was too high at low modulation frequencies and too low at higher frequencies. It is believed that with further development of the wind-tunnel techniques the distribution over the modulation frequencies of interest could be improved.