Frequency dependence of elliptical particle motion of acoustic waves transmitted into the seabed from a point source in water

Abstract

When perpendicular components of the particle velocity of a continuous acoustic wave have unequal amplitude and phase, the displacement traces an elliptical path. This is caused by inhomogeneous waves and/or losses in the medium. For spherical waves radiating from a point source in water and transmitted into the seabed, the orientation of the elliptical orbit varies with receiver location and frequency, and the ellipse major axis is not always parallel to the direction of propagation suggested by Snell’s law. If not accounted for, this could bias estimates of sediment sound speed derived from particle velocity measurements. This presentation describes a simple orbit model based on numerical evaluation of integrals for the transmitted field over the entire wavenumber range. The model provides rapid simulation of results for different experimental geometries and source frequencies. The model is validated using an established full-field model and compared with experimental data. [Work supported in part by ONR Code 32.]