I was inspired by the videos of Nils Berglund on youtube to try this example and see if I get similar results. Here the equation is u\_tt = A Delta u - B u\_t with certain coefficients. In the domain of the ellipse the cofficient of the laplacian is only 0.45 as strong. This represents the change of refractive index. In the video description there is information on how you can play with this simulation yourself.