This benchmark problem consists of a vibrating surface, which coincides with the spherical one. The plain surfaces of the missing octant are assigned a zero admittance. Thereby, the radiator allows construction of a smooth solution that will make it easy to identify solution failures caused by the ill–conditioning of the integral operator for techniques that solve the Helmholtz equation in an integral formulation, i.e. the irregular frequencies. Furthermore, the cat’s eye structure is a more complicated shape than a sphere and hence, the solution is expected to expose more irregular frequencies in a BEM solution than the sphere. A detailed description with references can be found in the PDF description. Available solutions: Steffen Marburg's solution using the Boundary Element Method: LA_Case2_CatEye_SteffenMarburg.pdf