An equivalent source method for recovering and reconstructing the target sound field in a non-free field

In a non-free field, the existence of disturbing sources would destroy the free-field condition required by near- field acoustic holography, and confuse the identification of target source due to the scattering effect caused by disturbing sound falling on the target source. To totally remove the influence of disturbing source, a method for recovering and reconstructing the target sound field in a non-free field was proposed based on the equivalent source method and the pressure-velocity measurement. In the proposed method, the sound field separation technique was firstly used to separate the mixed sound field into the outgoing field coming from the target source and the incoming field coming from the disturbing source. Then the scattered component contained in the outgoing field was calculated by using the disturbing sound and the surface impedance of the target source. Finally, the sound field radiated by the target source in a free field was obtained by subtracting the scattered component from the outgoing field and was further used to reconstruct the sound field of the target source. The proposed method was numerically and experimentally testified and the results of both the simulation and the experiment demonstrated the validity of the proposed method.