High-resolution nearfield acoustic holography based on iterative weighted equivalent source method

摘要

Because of the ill-posed nature of equivalent source method (ESM)-based nearfield acoustic holography (NAH), regularization methods based on the minimum L2-norm criterion such as the Tikhonov regularization are usually employed to stabilize its reconstruction procedure. However, the minimum L2-norm constraint sometimes makes the reconstruction result too smooth and thus degrades the spatial resolution of NAH, because this kind of constraint tends to disperse the acoustic field energy on the hologram surface to all the equivalent sources. To deal with this problem, an iterative weighted ESM (IWESM) is proposed, in which an iterative weighted regularization procedure is developed to solve the strengths of equivalent sources. The IWESM can reduce the dispersion of acoustic field energy on the hologram surface to those equivalent sources that contribute little to the acoustic field, and get more reasonable solution of source strengths. The validity of the IWESM is proven by a numerical simulation, and the result shows that comparing with ESM-based NAH, the proposed method can significantly improve the spatial resolution of reconstruction results.