Active noise absorption (ANA) by multisources in free field

In this paper, the ANA in space was discussed for arbitrary primary acoustic field. A general formula for calculating the optimal complex strengths of secondary sources was derived. The physical mechanisms of ANA was explained by using a general source radiation impedance-based approach. On this basis, the characteristics of ANA were discussed with two monopoles in primary acoustic field of plane wave as an example. The relation between absorbed power and location of two secondary sources was discussed and the absorbed area was obtained. All the theoretical results are verified by the experiments carried out in a semi-anechoic room and the absorbed noise effects are satisfactory.