The principle of an active scatterer based on the JMC method

The principle of formulating the JMC method to produce secondary sources that function as active scatterers on a hypothetical scattering surface is established. The principle can be applied, e.g., in the active control of interior spaces where changeable acoustical properties or adding sound quality and comfort are needed. The examination is based on the modified JMC method, to ensure that the logic does not lead to the need of changing the primary sources. The actively reflecting plane serves as an example of the JMC formulation for the active scatterer. The solution for the actively reflecting plane works on the local control principle: each reflecting subarea needs information of the primary field only at that subarea. The solution can also apply to piecemeal planar surfaces and to smooth convex surfaces, approximately. More versatile active scatterers, the boundary condition elements and the scattering–absorbing elements, do not generally work on the local control principle. With those elements any homogeneous boundary condition can be realized and original boundary conditions can be changed to any desired ones.