Abstract
The tonal noise source and the corresponding instantaneous velocity field around an aerofoil NACA0018 are measured to understand the mechanism of aerodynamic noise. The source measurement indicates that the tonal noise is generated from the rear side of pressure surface of the aerofoil. The simultaneous measurement of velocity field by PIV in reference to the sound pressure signal shows that highly correlated patterns of vortex shedding with respect to the sound pressures are generated from the trailing edge of the aerofoil. Therefore, the tonal noise could be generated by the periodic formation and shedding process of vortices from the trailing edge of pressure surface.
