The Relative Amount Measurement New Method And Technology Of Acoustic Parameter Of Seafloor Sediments

Seafloor sediment palys an important role in ocean physics and engineering, and its acoustic characteristic has been researching by the scholars at home and abroad. Seafloor sediments acoustic characteristic mainly contains two parameters: the sound velocity and acoustic attenuation. Current methods for measuring the sediment acoustic properties in laboratory belong to the absolute measurement method. Since the sediment is easy to deform, and its attenuation is big, it is hard to judge the first wave of sound waves accurately; and the disturbance in the process of absolute measuring is large, these all bring bigger error to measurement results. Therefore, in order to meet the needs of the seafloor sediments acoustic characteristic research, on the basis of preliminary study, this thesis put forward a new method for measuring named the relative measurement method. At the same time, the current measuring instruments commonly used8-bit A/I) sampling, data accuracy is not high, so on the basis of these, a multichannel acoustic signal measurement system is developed which use acoustic probe as sensors and high precision A/D converter and complex programmable logic device as the core. Then the sediment acoustic characteristic has been studied, and the acoustic transmission signal between the sediment sample cross section was obtained.The thesis introduces the research status quo ofseabed sediment laboratory measurement,andoutlinesthemainacousticcharacteristicsparametersof sealloor sedimentsandthemanufacturemethodsof sedimentsamples.Usingrelative measurement method proposed in this thesis, analyzed the sediment acoustic velocity and attenuation features, and designed a new type of ultrasonic signal measurement system.Thewhole systemconsists of two parts:digitalsignalprocessingsystem and ultrasonicsignal generation system.This thesisr mainlyintroduced the digitalsignal processing system in detailed, through introducing the hardware module of each part, built the hardware platform of digital signal measurement system. In terms of hardware module, control signalreceiving module of the acoustic meter system, the ultrasonic wave signal receiving module and digital signal uploading module are given, and the interface circuit of data acquisition module is introduced in detail. On software, through programming of CPLD device, download the working parameters of the acoustic meter control system to the lower place machine to make the whole system work in accordance with set parameters, and convert analog sound wave signal in the sediment to14-bit signal and then store it in an external double-port RAM; write the upper machine data reading and processing program with VB6.0, and its working flow chart is presented.In order to verify the accuracy of the new acoustic instrument, we made a preliminary measurement experiment. We get the ideal waveform in the experiment that we used a onic probe to receive the signal source of sinusoidal and pulse signals. We combine the problems and deficiencies which found in the experimental measurements, and put forward ours opinions on the further improvement about the measurement system.