Title: The Effects of Unsteady On-Road Flow Conditions on Cabin Noise: Spectral and Geometric Dependence
text: The in-cabin sound pressure level response of a vehicle in yawed wind conditions can differ significantly between the smooth flow conditions of the aeroacoustic wind tunnel and the higher turbulence, transient flow conditions experienced on the road. Previous research has shown that under low turbulence conditions there is close agreement between the variation with yaw of in-cabin sound pressure level on the road and in the wind tunnel. However, under transient conditions, sound pressure levels on the road were found to show a smaller increase due to yaw than predicted by the wind tunnel, specifically near the leeward sideglass region. The research presented here investigates the links between transient flow and aeroacoustics. The effect of small geometry changes upon the aeroacoustic response of the vehicle has been investigated. It was found that sideglass pressures showed close agreement at all turbulence levels while surface sound pressure levels also showed similar behaviour under a wide range of on-road flow conditions. While the overall sideglass sound pressure level changed under the various yaw conditions, the change in shape of the frequency spectrum was less significant. Geometry changes made to a base vehicle reduced the sensitivity of the in-cabin noise to on-road turbulence, showing that shape-change can modify sensitivity to on-road turbulence.