The purpose of this study is to investigate the characteristics of aerodynamic sound generated from wake interference of circular cylinder and airfoil vane located in tandem and to clarify the generation mechanism of the sound source with discrete frequency. The effects of the interval between the cylinder and the airfoil on the characteristics of aerodynamic sound are investigated by acoustic measurement, flow visualization and exploration test of sound source. The relation between the flow field and the sound field with discrete frequency noise (DFN) is shown, and then it is found that the downstream airfoil works as the sound source of DFN, which has the frequency of vortex shedding from the upstream cylinder, when the interval of two bodies is longer than a critical distance.