TAKING INTO ACCOUNT THE EFFECT OF THE FREE-BOUNDARY IN CALCULATING THE ACOUSTIC FIELD IN A MEDIUM WITH A SUBSURFACE DEFECT

The authors examined the wave field in a halfplane weakened by a subsu rface inclusion or a cavity. The use of the long-range field approxima tion [1] for these defects results in a very large error. In this case , the problem is reduced to a system of boundary integral equations at the boundary of the inclusion (or to a single equation in the case of a cavity). The boundary element method is used to calculated the wave field on the surface of the halfplane in the zone close to the defect .