Geoacoustic Inversion for Bottom Parameters in the Deep-Water Area of the South China Sea**Supported by the National Natural Science Foundation of China under Grant Nos 11434012, 41561144006, 11174312 and 11404366.

Abstract

Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss (TL) data in the shadow zone of deep water. We propose a multiple-step TL inversion method to invert sound speed, density and attenuation in deep water. Based on a uniform liquid half-space bottom model, sound speed of the bottom is inverted by using the long range TL at low frequency obtained in an acoustic propagation experiment conducted in the South China Sea (SCS) in summer 2014. Meanwhile, bottom density is estimated combining with the Hamilton sediment empirical relationship. Attenuation coefficients at different frequencies are then estimated from the TL data in the shadow zones by using the known sound speed and density as a constraint condition. The nonlinear relationship between attenuation coefficient and frequency is given in the end. The inverted bottom parameters can be used to forecast the transmission loss in the deep water area of SCS very well.