Analysis of sound transmission through the sea surface in shallow water

Different paths of sound waves penetrating through air into water are examined by use of both ray theory and wavenumber spectral integration method.Some comparisons with the experimental data are also given.It follows from the results that the main contribution paths to the underwater acoustic field in shallow water are the direction path and the successive bottom reflection path.The contribution of the direct path concentrates mainly around the area just below the air-borne source.With the range increasing,the propagation loss of the direct path increases remarkably because of the spread loss and shadow zone effect.The main contribution to the long-distance underwater acoustic field comes from the bottom reflection path,including the multiple reflection paths of the bottom and sea surface.