Influence Factors of Noise Reduction for a Cluster Active Control System in Free Space

Comparing with the centralized active noise control system, a cluster system has the advantages of low implementation costs and flexible extensions, hence it is helpful to examine the influence factors of noise reduction performance of the cluster active system for engineering applications. Firstly, a theoretical model is established and the optimal strengths of secondary sources are obtained using the least square method. Then sufficient conditions related to equivalent performances of the cluster and centralized system are derived. Finally, the influence of unit partition and layout on noise reduction is analyzed when the equivalent condition cannot meet in a free space. The results demonstrate that when the number of the error sensors are less than or equal to that of secondary sources, and the acoustic impedance matrices of the control units and the system are both full rank, the cluster system is equivalent to the centralized system. When the equivalent condition isn't met, the performance of the cluster system degrades small if for each unit both of the following conditions are satisfied: a) the number of the error sensors should be greater than or equal to, or all smaller than or equal to the number of the secondary sources; b) the sub-impedance matrices should be full rank.