Ochmann M., Piscoya R.

The source simulation technique is a general tool for calculating the sound radiation or scattering from complex-shaped structures into the three-dimensional space. The basic idea of the method consists in replacing the structure by a system of acoustical sources placed in the interior of the structure. By definition, these source functions have to satisfy the Helmholtz equation and the radiation condition. For solving the radiation or scattering problem completely or approximately, the source system also has to fulfil or minimize the boundary conditions on the surface of the body. In most cases, spherical wave, functions e.g. monopoles, dipoles, quadrupoles etc. with different source locations are used as sources, since they can easily be calculated. If the coordinates of the source positions are shifted from real values into the complex plane, the corresponding monopoles show a similar behaviour like surface waves or possess a distinctive directivity pattern, depending on the values of the imaginary parts of their coordinates. Therefore, by adding such complex source point solutions to the system of equivalent sources, strongly focused sound field should be computed in a more efficient and stable way. The capacity of the extended source simulation technique is investigated and represented by applying it to selected radiation problems.