A Simple Tank Test for Inversion of Equivalent Acoustic Impedance of an Underwater Flat Plate

This paper presents a basic experimental study on the evaluation method for determining the equivalent acoustic impedance of an arbitrary material flat plate. The study applies an inversion method based on the complex sound speed of the acoustic material, utilizing reflectivity measurement results. To achieve this, an equation for calculating reflectivity which incorporates the equivalent acoustic impedance of the flat plate and the acoustic impedance of the contacting media, was adopted. A procedure for inverting the equivalent acoustic impedance of the plate was developed by numerically solving this equation, incorporating the reflectivity measurement results. Additionally, the validity of the method was assessed through a series of reflectivity measurements conducted for an acrylic flat plate in a simple water tank, using an omni-directional acoustic source. The equivalent acoustic impedance inversion was then performed based on the measurement data. The results demonstrate that the inversion method for determining the equivalent acoustic impedance of an arbitrary material flat plate, using reflectivity measurements, can be effectively applied to evaluate the equivalent acoustic impedance of acoustic materials attached to submarine hulls.