Seabed parameter estimation by inversion of long range sound propagation fields

The seabed parameters are especially important in underwater sound propagation in shallow water. A long range geoacoustic inversion experiment was conducted in January 2005, in winter conditions in the South China Sea where the bottom is mostly sand and silt. In this experiment, single frequency CW pulse signals were transmitted from a suspended source, and received by a vertical array of hydrophones. The data were inverted for the geoacoustic properties of the seabed using a hybrid inversion method-the adaptive simplex simulated annealing (ASSA). Owing to the identical inversion procedures, the favorable results were obtained for 6 unknown geometrical and geoacoustic parameters by the semi-infinite seabed model. It is shown that seabed inversion parameters are consistent for the different time arrival signals. By comparing with the inversion for a sediment over basement bottom model, the single layer seabed geoacoustic model is adequate to obtain the equivalent seabed parameters very well for the long range experiment site.