Numerical predictions of transient acoustic scattering from a tyre-shaped object inside the seabed are compared with data from a sea trial at a shallow water site in the Baltic Sea. A ROV-mounted parametric transmitter was used to insonify the object at oblique incidence angles, and the scattered field was registered by an eight-hydrophone vertical array as well as a single hydrophone placed on the seafloor vertically above the tyre. The numerical predictions are computed by a high-order frequency- domain boundary-integral equation (BIE) method for acoustic scattering from smooth 3D bodies in a layered fluid-solid medium. Transient fields are computed by Fourier synthesis, employing a linear combination of an ordinary and a hypersingular form of the BIE to avoid ill-conditioning from artificial singularities. The observed data show a good ping-to-ping consistency, indicating a satisfactory stability of the experimental conditions. A good agreement between the predicted and the experimental waveforms is observed at receivers in high signal strength locations. The spatial distribution of scattered energy is found to agree well with model predictions in directions near the specular scattering angle, while showing some evidence of unmodelled effects of roughness and seabed inhomogeneity in directions outside the bottom-reflected main lobe.
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