These parameters control the reverberation computation. CPH is the phase velocity of the incident field component for which the scattering kernel should be computed. Only has significance for options I, S and c, otherwize it is dummy.
INTFC is the number of the rough interface for which the scattered field or reverberation has to be computed. The roughness for that interface must be specified in the corresponding line in block IV. Note that the uppermost interface (lower boundary of upper halfspace) is interface number 2!