Methods Of In-situ Acoustic Measurement And Acoustic Characteristics Study In Seafloor Sediment

Electromagnetic waves and other methods are difficult to meet the needs of the people to detect the seabed,such as the attenuation of the electromagnetic waves in seawater and the limited propagation distance.Acoustic wave has good propagation characteristics in seawater,so acoustic detection method plays an important role in ocean detection.In addition,the sound velocity and attenuation of seafloor sediments are of great value to underwater acoustic communication,seabed construction and disaster monitoring.Therefore,the study of the ground-acoustic characteristics of seafloor sediments has always been the focus of scientific research institutes and experts in various countries.Because it can maintain the original environment of seafloor sediments well and reduce the disturbance of sample,in-situ acoustic measurement technology can obtain more accurate acoustic parameters of seafloor sediments.At the same time,in-situ acoustic measurement technology will not limit the test frequency range because of the sample size.In this paper,a new in-situ acoustic measurement system for seafloor sediments is introduced in detail,including its working principle,system composition and technical specifications.The wave propagation process of a new in-situ acoustic measurement system is numerically simulated and analyzed based on Biot model.In this paper,the method of insitu acoustic data processing is studied and the method of STA/LTA in-situ acoustic velocity extraction is established.A new in-situ acoustic measurement system of seafloor sediments was used to measure sediments in the north of Hangzhou gulf and the East China Sea Zhoushan Qundao,and the gas phase distributions and content of sediment samples were obtained by CT nondestructive testing.The relationship between free gas and in-situ acoustic properties in seafloor sediments was studied.The results show that the sound velocity of seafloor sediments in the northern part of the Hangzhou gulf and the East China Sea is negatively correlated with their gas content,and the sound velocity of seafloor sediments in the sea area near the East China Sea are much higher than that of the Zhoushan Qundao in the north of Zhoushan Qundao.The sound attenuation of seafloor sediments in the northern part of Hangzhou gulf and the East China Sea is positively correlated with their gas content,at the same time,when the gas content is less than 2%,the acoustic attenuation of seafloor sediments in the Zhoushan Qundao area near the East China Sea is slower than that in northern Hangzhou gulf,when the gas content is more than 2%,The acoustic attenuation of seafloor sediments near the Zhoushan Qundao of the East China Sea is more severe than that in the northern Hangzhou gulf sediments.