Sensitivity analysis of the acoustic field in shallow water to environmental parameters

Abstract

Environmental parameters, such as sound-speed profile and bottom structure, have very important effects on the acoustic propagation in shallow water. In this paper, some detailed simulations are presented for a typical shallow water with a thermocline. The simulated properties include the coherent and incoherent transmission loss, averaged energy loss, group velocity, phase of the acoustic field, and the multipath arrival structure. The concerned environmental parameters include surface speed, thermocline depth and thickness, water depth, bottom structure, and its geoacoustic parameters. The results show that the coherent transmission loss and the phase of the acoustic field are sensitive to the environmental parameters, while the other properties are relatively stable. Theoretical explanations of these results are also given. Both the sensibility and the relative stability can be utilized. Through reasonable cost function design, the former can be used to invert the geoacoustic parameters of the bottom, while the latter can be used to localize distant targets. Finally, the geoacoustic parameter inversion for a complicated bottom is given by using the real data from a vertical line array. With the obtained bottom parameters, experimental transmission loss is well explained.