A MIMO-system for a 2-dimensional active noise control application

In active noise control a given sound field called primary field is superposed by a secondary field, which is generated with the aim to cancel or at least to attenuate the primary field. For this both fields have to have exactly the same amplitude, but the opposite phase. A long wave length and a simple structure of the primary field make the superposition easier. Therefore, when DSPs are fast and accurate enough, the cancellation of low frequency noise in a duct (Nelson and Elliott, 1992; Morgan) (e.g. in an air condition system) was one of the first commercial application. Compared with this one-dimensional situation ANC in two dimensions is much more complicated (Doelman, 1993). Here a system should be described, which controls the noise in a two-dimensional bounded area. Results of simulations and measurements are showing principal limits and the performance of the system. Possible strategies of adaptation are discussed at the end.