Modelling and characterization of acoustic wave propagation in seabed

Abstract

In this paper, acoustic wave propagation in water-saturated sand under controlled laboratory conditions is investigated. Our method uses a combination of two fundamental frequencies f1 & f2 generated using piezoelectric transducers placed on the surface of the sand, simulating seabed with fresh water and sand. The interaction of sound (acoustic) waves in a dispersive but homogenous medium will typically generate harmonics and intermodulation terms (intermod). These interactions result in perturbations as the sum and difference frequencies. The results show that the amplitude of the intermodulation products is inversely proportional to the density and thickness of the buried inhomogeneity. For instance, 2nd order intermod term show 2 dB decreases in amplitude for 7 mm increase in thickness at constant density of plywood. For constant thickness at 5 mm there is 10 dB drop in same intermod term for change in density from plywood 550 Kg/m3 to copper 8930 Kg/m3.