The NDT Problem Solver Software is an old DOS based Utility. Three modules are available,
http://www.ndt.net/publicat/bibliog/pss.htm
Prof. Igor N. Ermolov derived equations for “equivalent reflectors”. These are an extension of the concepts made popular by the brothers Krautkramer in the 1960s and allow the calculation of ideal amplitude responses to
http://www.ndt.net/article/v07n01/ginzel/ginzel.htm