Range-dependent geoacoustic inversion for sound propagation in two seamounts environment

Abstract

This paper presents a work of range-dependent geoacoustic inversion for two seamounts environment with negative gradient sound speed profiles based on the transmission losses (TLs), collected in an experiment in the South China Sea, 2016. Bombs of 200 m and the mooring vertical line array (VLA) is applied for recording. Typical characteristics of shadowing and reflecting by seamounts are confirmed by the fluctuations of TLs with respect to range, indicating the complexity of sound propagation within seamounts environment. In the framework of matched field inversion (MFI), the geoacoustic model of two layers and the range-dependent acoustic model (RAM) is applied to produce the replica TLs, which is used to compute the cost function in combination with the collected TLs in terms of the least mean variance. The simulated annealing (SA) is expected to augment the searching efficiency of geoacoustic parameters. Results of four models with different parameters within 120km are obtained, with which the simulated TLs are in good accordance with experiment results for several frequencies and receiving depths. Conclusion is drawn that the effects of range-dependence of geoacoustic parameters in seamounts environment are as important as those of bathymetry on sound propagation, which should be seriously considered especially with negative gradient sound speed profiles.