The aerodynamic noise from a two-dimensional symmetrical airfoil was studied experimentally using a low-noise acoustic wind tunnel. The measurement of the sound spectrum at Reynolds number 1.6×10 5 indicates the generation of discrete frequency noise from the airofoil at small incidence angles. The surface flow visualizations over the airofoil were carried out using the oil-film method and the shear-sensitive liquid crystal technique. These visualization results indicate that the reattachment

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... d reseparation of the flow occur near the trailing edge of the pressure side of the airfoil, when the discrete frequency noise is generated. The smoke-wire visualization of the flow around the airfoil showed that the strong trailing edge vortices were shed from the airofoil and they form a stable pattern of Karman vortices in the downstream. Aerodynamic sound, Flow visualization, Vortex shedding, Symmetrical airfoil Schematic illustration of acoustic wind tunnel.