Active noise absorption by multisources in free field

In this paper, Active Noise Absorption(ANA)in space is discussed for arbitraryprimary acoustic field. A general formula for calculating the optimal complex strengths ofsecondary sources is derived. The physical mechanisms of ANA is explained by using a general source radiation impedance-based approach. On the basis of the discussion,the characteristics of ANA are discussed with two monopoles in primary acoustic field of plane wave as anexample. The relation between absorbed power and location of two secondary sources is discussed and the absorbed area is obtained. Finally,all theoretical results are verified by experiments carried out in a semi-anechoic room and the absorbed noise effects are satisfied.