Abstract
The aim of this investigation is to clarify generation mechanism of aeroacoustics feedback of rearview mirrors for automobiles. To understand relationship between flow field and tonal noise, wind tunnel experiments were carried with a backward-facing step and small bump. The experimental results showed that the strong tonal-noise was observed when the height of the bump was almost equal to 40% of height of the boundary layer. Correlation in terms of velocity fluctuation and tonal-noise was high at the edge of backward-facing step. Strong correlation was also observed just behind the small bump. The disturbances from the small bump therefore seem to be the seeds of the tonal-noise. In order to understand the effect of edge shape of backward-facing step, acoustic field around the edge of step was calculated. The acoustics filed depended on the edge shape of the back-step. The result of wind tunnel experiments showed the tonal-noise was not observed in the case of the back-step with large round-edge.
