Acoustic pressure simulation and experiment design in seafloor mining environment

Abstract

Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor mining environment. Based on the KZK (Khokhlov-Zabolotkaya-Kuznetsov) equation, the method of sound field analysis in turbid water is proposed. Firstly, based on the analysis of absorption in clean water and viscous absorption of suspended sediments, the sound attenuation coefficient as a function of frequency in the mining environment is calculated. Then, based on the solution of KZK equation in frequency domain, the axial sound pressure of transducer in clear water as well as turbid water is simulated using MATLAB. Simulation results show that the influence of the suspended sediments on the pressure of near field is negligible. With the increase of distance, the axial sound pressures of transducer decay rapidly. Suspended sediments seriously affect the pressure in far-field. To verify the validity of this numerical method, experiment is designed and the axial sound pressure of transducer with a frequency of 200 kHz and a beam width of 7.5° is measured in simulated mining experiment. The results show that the simulation results agree well with the experiments, and the KZK equation can be used to calculate the sound field in turbid water.

Keywords

seafloor mining / acoustic pressure / KZK equation / turbid seawater / sound attenuation

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