In this paper, a room acoustics simulation using a finite difference approximation on a face-centered cubic (FCC) grid with finite volume impedance boundary conditions is presented. The finite difference scheme is accelerated on an Nvidia Tesla K20 graphics processing unit (GPU) using the CUDA programming language. A performance comparison is made between 27-point finite difference schemes on a cubic grid and the 13-point scheme on the FCC grid. It is shown that the FCC scheme runs faster on the Tesla K20 GPU and has less numerical dispersion than best 27-point schemes on the cubic grid. Implementation details are discussed.