OK.. on to the eigenvalue problem.

I started with the quantum program... and stripped out all the quantum stuff. ;-)

Basically the acoustics problem is exactly the square well potential (V=0 everywhere) BUT with different boundary conditions.

In quantum_common.py we've got:

    ebc_1 = {
        'name' : 'ZeroSurface',
        'region' : 'Surface',
        'dofs' : {'Psi.0' : 0.0},

Which forces psi to be zero on the surface of Omega. Basically Dirichlet conditions. For acoustics the velocity potential needs to have no normal gradient at the surfaces.. more or less Neumann conditions. Is there an easy way to implement that?