Reconstruction of the sound field above a reflecting plane using the equivalent source method

Abstract

In practical situations, vibrating objects are usually located above a reflecting plane instead of exposing to a free field. The conventional nearfield acoustic holography (NAH) sometimes fails to identify sound sources under such situations. This paper develops two kinds of equivalent source method (ESM)-based half-space NAH to reconstruct the sound field above a reflecting plane. In the first kind of method, the half-space Green's function is introduced into the ESM-based NAH, and the sound field is reconstructed based on the condition that the surface impedance of the reflecting plane is known a prior. The second kind of method regards the reflections as being radiated by equivalent sources placed under the reflecting plane, and the sound field is reconstructed by matching the pressure on the hologram surface with the equivalent sources distributed within the vibrating object and those substituting for reflections. Thus, this kind of method is independent of the surface impedance of the reflecting plane. Numerical simulations and experiments demonstrate the feasibility of these two kinds of methods for reconstructing the sound field above a reflecting plane.