I take the opportunity to answer a very old question with no reply. I hope it will be helpful for others in the future.
In the meantime juuli has developed a solver for the finite differences in the time domain (FDTD) approach so calculate a sound field. The name of the project is "Parallel FDTD" and can be found on Github. The solver uses CUDA to accelerate the calculations using your graphics card:
A FDTD solver for room acoustics using CUDA
https://github.com/juuli/ParallelFDTD
