Acrylic plate acoustic transmission experiment and theory

Abstract

An approximate model of the transmission of sound waves in water through a plate of PMMA was developed for a point source. The model is based on spherical wave propagation and plane‐wave transmission through a solid layer, and it is calibrated by identifying the properties of the plastic. By minimizing the error between the modeled and the experimentally measured acoustic wave, the mechanical properties of PMMA can be estimated for PMMA plates of varying thickness d for the d/fluid range of 0.04 to 2.5, and sound‐incident angles of 0 deg to 35 deg. This calibration requires only the compression wave ray‐path information and was shown to achieve 90% correlation between experimental and predicted waveforms for synthetic cavitation pulses with a nominal bandwidth from 40 kHz to 200 kHz. At larger angles of incidence as measured based on the compression wave, it was necessary to track the various waves that occur in the solid, i.e., compression, shear, and evanescent. The acoustic pressure waves that they generate have to be appropriately added at the receiver location to then recreate the experimentally‐measured acoustic signal. The achieved model‐experiment correlation at these greater angles of incidence was 80%. [Work supported by ONR.]