Plane wave reflection coefficient from near field measurements

The plane wave reflection coefficient for all angles and frequencies is a unique descriptor of the acoustic properties of a seabed, but it is difficult to measure directly in shallow water. However, one can calculate the point receiver result by a plane wave expansion given the plane wave reflection coefficient. In this paper it is shown that it is also possible to perform the more useful inverse operation of calculating the plane wave reflection coefficient given point source and receiver measurements. This means that it is possible to make propagation predictions in the presence of complex bottom structure using short range reflection measurements but without ever determining the detailed geoacoustic parameters. Simulations show that the method works for multiple isospeed layers and also continuously varying sediment sound speed profiles. The feasibility of experimental determination of the plane wave reflection coefficient is addressed. (C) 2004 Acoustical Society of America.