Modeling sea state induced atmospheric sound transmission loss

Abstract

This work presents a numerical study on atmospheric sound propagation over rough rigid surfaces. The intent is to simulate acoustic propagation over water. Methods to estimate sea state induced atmospheric sound transmission loss and relative uncertainties are evaluated. In previous studies, a flat surface with an equivalent impedance was used to account for the effect of surface roughness on sound transmission loss. Equivalent impedances were estimated based on time-domain numerical simulations of atmospheric sound propagation above pseudorandom sea surfaces coherent with a Pierson-Moskowitz spectra. Estimation of equivalent impedances using time- and frequency- domain approaches are compared for cases up to sea state 4. Acoustic excess attenuation due to propagation over a rough surface was predicted by the authors, in a previous work, by correcting the excess attenuation of a propagation over a flat, perfectly reflecting surface. The correction factor was frequency and sea state dependent and included an additional term to account for the uncertainties characteristic of different sea states. Excess attenuation predictions estimated using the equivalent impedance approach are compared with those obtained from the authors’ previous study. Implications of the use of these methods for source detectability determinations are discussed.