The Experimental Study On Small-scale Sound Field In The Seabed Sediment Based On Ultrasonic Probe

The study on seabed sediment has a great meeting in the fields of economic construction and national defense. At present, the acoustic measurement based on ultrasonic is the main way to surveying the seabed sediment, to study the physical property and internal structure of the sediment by the sound velocity and sound attenuation. The research on seabed sediment mostly based on the in situ measurement and the laboratory measurement.It presented the definition of the seabed sediment, the representation of seabed sediment acoustic characteristics and the basic principles of sediment acoustic attenuation. It introduced the mainstream method of sediment acoustic measurement—differential measurement. It introduced the typical methods of in situ measurements and laboratory measurements, analyzed the measuring principles and merits and demerits of the typical laboratory measurements comparatively.In view of the measuring demerits that the results of measurement of the whole sample can not reflect the sound field of the sample, it presented to study the sound field of the small-scale seabed sediment by the measurement which is meet the differential analysis of sound field, to study the acoustic attenuation properties and the acoustic velocity of the small-scale sample of seabed sediment.In order to meet the measuring density and the small sample disturbance in the measurement, it protocolled two measurements of fiber-optical grid and ultrasonic probe. It verified the two methods respectively by experiment and confirmed the ultrasonic probes as the measurement method to study the sound field of small-scale seabed sediment for its feasibility.Combined the measuring principles of sound field of small-scale seabed sediment with the ultrasonic probe, it designed the experiment platform and made the manual tubular sample by the seabed sediment which was collected by the Chinese academy of sciences, the south china sea institute of marine research in the south China sea in Dec.2010. It verified the initial phase of the wave received by the ultrasonic probe in the water. The measurement experiment was carried by the flat transducer and ultrasonic probe with 40KHz to study the sound field in the small-scale sediment, including the acoustic attenuation properties and the acoustic velocity in the small-scale sample of sediment. The regression analysis on the amplitude of the measuring point was carried, the acoustic attenuation in the sediment can be described well by the exponential function model. It studied the relation between the depth of ultrasonic probe into the sediment and the measurement of the acoustic characteristics of the sediment. According to the data collected by the ultrasonic probe in the sediment in 3 different depths, found that the acoustic velocity in the tubular sample meet the velocity gradient of viscous movement of the plane wave in the pipe while no visible changes in the acoustic attenuation.According to the deficiencies found in the experimental operation and the problems found in the analytical processing of the experiment data, the paper presented the improvements to the study of small-scale sound field in the seabed sediment based on ultrasonic probe measurement.