A geoacoustic inversion method based on bottom reflection signals

Abstract

It is important for underwater acoustic modeling and passive localization to estimate the geoacoustic properties with high accuracy. A geoacoustic inversion scheme was presented, which uses a broadband source to generate the linear frequency-modulated signal at different ranges and depth. The signal was received by a vertical array. The bottom reflection loss was extracted by matched filtering and then used to estimate the sea-bottom density and sound speed. Meanwhile, an inversion method based on sub-bottom reflection was investigated using the experimental data. Because the direct arrivals in the water were influenced strongly by the internal waves, the first sea-bottom reflection was taken as the reference path to calculate the relative arrival time and amplitude of sub-bottom reflections. Firstly the sediment sound speed and thickness were estimated using different source depth and receiver depth. Then the sediment attenuation was estimated by assuming that it has linear frequency dependence. The estimated values of the sediment properties compared well with the core data, chirp sonar data, and the matched field inversion results.