Study On The Acoustic Measurement Characteristics Of The Seabed In-situ Acoustic Measurement Head

In-situ measurement methods and laboratory measurement methods are often used to obtain the sound velocity and sound attenuation coefficient of seabed sediments.The in-situ measurement method is used to measure the seabed sediments,which can obtain the in-situ acoustic measurement characteristic of the seabed and has little disturbance;Firstly,the laboratory measurement method needs to collect sediment samples,although it exists disturbance in the process of storage and transportation to the laboratory,while obtaining the acoustic properties,a series of physical properties such as density,porosity,elastic modulus,and water content can also be obtained.Therefore,in-situ measurement method and laboratory measurement method have certain advantages and disadvantages.The two are complementary.The current seafloor in-situ observation device needs to be able to simultaneously achieve in-situ measurement and sampling of seafloor sediments,so that the in-situ sound velocity,sound attenuation of seafloor sediments and the acoustic physical characteristics of sediment samples can be studied more accurately,so as to achieve the establishment of original data.The connection bridge between in-situ measurement and laboratory measurement are in order to obtain as much as possible the sound velocity and sound attenuation consistent with in-situ measurement.At the same time,accurately obtaining the acoustic parameters of seabed sediments in many fields is an important prerequisite for people to understand the sound speed and sound attenuation of seabed sediments.Usually,the method of extracting seabed sediment acoustic signals is used to calculate the sound speed and sound attenuation coefficient.When processing measurement data,in order to improve the reading efficiency and avoid errors,it is necessary to design a reasonable algorithm to process the acoustic signal.The main research contents of this paper are as follows:1.Complete the overall plan design of the in-situ acoustic measuring head through the structure,function,and measurement principle analysis of the in-situ acoustic measuring head,including the introduction of acoustic probes,temperature measuring probes and other components of hardware and unit composition;2.Select the data obtained from the static calibration measurement of the in-situ acoustic measuring head under the condition of pure water at a depth of(28)mh 25.0,and focus on the comparative analysis.The take-off point interpretation method,feature point interpretation method,automatic interpretation method,and cross-correlation are used the interpretation method extracts the sound velocity calculated from the acoustic signal,uses the amplitude envelope method and the spectrum analysis method to calculate the sound attenuation coefficient,and draws the corresponding conclusions.At the same time,they are integrated using MATLAB to build a GUI interface,which realizes Efficient and accurate processing of data;3.Use in-situ acoustic measuring heads to calibrate and measure pure water.Under static conditions,explore the effects of depth and boundary on sound speed and sound attenuation;under dynamic conditions,explore the effects of speed on sound speed and sound attenuation;4.Develop an experimental plan and build a seabed in-situ layered observation movement simulation experiment platform.The seabed environment with three different media of water,muddy sediment and sandy sediment was simulated in a high drum,and in-situ acoustic measurement was adopted.The heads carry out dynamic layered measurement and sampling respectively to verify that the in-situ acoustic measurement head can simultaneously realize the functions of in-situ acoustic measurement and sample sampling.