Experimental Investigation of Tonal-noise Generated from a Rear-view Mirror for Automobile

摘要

The aim of this investigation is to understand the generation mechanism of tonal-noise from rear-view mirrors. In order to clarify velocity fluctuation and radiated noise, correlation in terms of aerodynamic noise and velocity fluctuations were measured in a low-noise wind tunnel. The experimental results showed that noise level of the tonal-noise depended on the ratio of the height of the bump to the thickness of the boundary layer. Strong tonal-noise was generated when the thickness of the bump was almost equal to the half height of the boundary layer. However, tonal-noise was not observed when the height of the bump was almost the same as the thickness of the boundary layer. Tonal-noise was also disappeared in the case of the bump was placed at turbulent boundary layer or the downstream of the separation point. It revealed that the seed of the tonal noise was small disturbances generated by the bump on the surface of the rear-view mirror.