A 2D Helmholtz solver based on Combined Field Integral Equation (CFIE) formulation for acoustic scattering problems. It contains a half-space implementation based on a hybrid approach combining Sommerfeld integral and method of images. For ref: O’Neil, M., Greengard, L. and Pataki, A., 2014. On the efficient representation of the half-space impedance Green’s function for the Helmholtz equation. Wave Motion, 51(1), pp.1-13.