Acoustic remote sensing of shallow ocean sediment characteristics

Abstract

In this paper, a procedure is presented for estimating the acoustic parameters of shallow ocean sediments from the sound field measurements using a horizontal array. The sediment is modeled as a fluid with sound speed c at the water-sediment interface, a constant sound-speed gradient g, and a constant density ρ . Initially, the modal wave numbers k_m (m = 1,2,...,M) are estimated using the generalized pencil-of-functions method. Next, an iterative procedure is used for estimating (c,g,ρ ). This procedure is based on the fact that the phase change Φ _m of the modal waves at the water-sediment interface can be determined from the dispersion relation using the estimated values of k_m. The phase change Φ ^{^}_m of the modal waves can also be computed for any assumed values of (c,g,ρ ). Estimates of (c,g,ρ ) are obtained by adjusting their values so as to minimize the error Σ_m = ∑ _m(Φ _m-Φ_m)². Simulation results are presented to illustrate the method.