“…A subtlety of our approach is that, in order to close the system of equations, surface integral operators must be introduced which connect interface traces of the scattered fields (Dirichlet data) to their surface normal derivatives (Neumann data). Such Dirichlet-Neumann Operators (DNOs) have been widely used and studied in the simulation of linear wave scattering, e.g., for enforcing far-field boundary conditions transparently [2,3,8,9,15,19,21,22,35] and interfacial formulations of scattering problems [27,29,32,34,36].…”