ABSTRACT
At the present section we give a more complete solution for these triangles. First of all, we will understand why only these three types of triangles (among all others) admit exact analytical solution. Then we will construct an explicit›form representation of the Green’s function for the Helmholtz operator in these domains as an exponentially convergent series (which has not been made until now). But what is much more important is that the method proposed here will allow us to extend this result to some 3D polyhedrons (see the next section), where there are no analogous results at all. For all that, we will use the well known virtual›image technique. To be more specic, we restrict the consideration by the Neumann boundary value problem (the case of acoustically hard boundary surfaces).
