Geoacoustic Inversion for Bottom Parameters in the Deep-Water Area of the South China Sea

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.

Spatial correlation of the high intensity zone in deep-water acoustic field

“…The bottom sediment is core sampled in this experiment, and the results show that the surface bottom density is 1.6 g/cm 3 . Reference [14] inverted the bottom acoustic parameters near this experimental area and 124310-2 the attenuation coefficient was α = 0.78 f 2.08 dB/m, where the frequency is in units of kHz. In the signal processing, we first obtain the compressed pulse signal s c (t) by using the pulse compression technique which can increase the signal-to-noise ratio (SNR).…”

Deep-sea explosion sound signal propagation loss measurement and model verification

“…Dong et al conducted a numerical study of very low frequency sound field in deep sea 3D submarine mountain terrain using 3D spectral element methods [13]. Wu et al proposed a multiple-step TL inversion method to invert sound speed, density and attenuation in deep water environment [14]. Li et al inversed bottom parameters in a thermocline environment in the northern area of the South China Sea using the experiment data [15].…”

Geoacoustic Inversion for Bottom Parameters via Bayesian Theory in Deep Ocean

“…A significant difference from Ref. [11] is that our approach uses the Bayesian theory to invert bottom parameters. Moreover, considering that the sensitivities of shallow-zone TLs vary for different frequencies of the bottom parameters in the deep ocean, this research obtained bottom parameters at varying frequencies.…”

“…Similar to the approach in Ref. [11], the received signals carry substantial information for bottom parameters, especially the signals in the acoustic shadow zone that mainly consist of the bottom reflection energy. Therefore, the bottom parameters can be easily estimated from the transmission loss (TL) of the shadow zone.…”