Vortex sound in the presence of a wedge with inhomogeneous surface flow impedance

The low Mach number vortex sound scattered by a sharp wedge formed by a rigid and an acoustically softer material is analyzed theoretically in the present investigation. A general expression for the time-varying far field potential due to the incompressible vortex motion around the edge of the wedge is derived to the leading order of magnitude. Results show that the introduction of a softer material increases the far field sound pulse magnitude. Also, it is found that the lower the impedance of the material, the louder the far field sound will be. In addition, it is shown that the effective fluid density inside the porous material is more important that the flow resistance in affecting the far field sound pulse magnitude when a weak vortex is concerned.