Abstract: The Von-Karman vortex street flow around a circular cylinder is successfully solved at Re=100,with the ADI-BGE schemes and the recent treatment of body boundary conditions being applied and a new acceptable pertubation model to being introduced solving incompressible N-S equations in the form of stream function and vorticity.The solutions of the flow field obtained are better than previous numerical ones,and agree with the experimental data more closely.Therefore,it can be used to study sound field numerically.As for computation of sound field,the Curie equation is directly and numerically solved to analyze the distribution of sound sources and the characteristics of their radiated sound field at Re=100 and to compare with the solutions from the theory of vortex sound and the spectrum of the fluctuating force and separated vortices in the flow field.It is shown that this method is more successful.