Measuring the sound speed in deep-sea first sediment layer using a high-frequency submersible sub-bottom profiler: Method and sea trial application

In the study of sedimentary acoustics, measuring sound speed in the first layer sediment is a key issue. To solve this problem, we proposed a method for measuring the sound speed in the deep-sea first-layer sediment using a high-frequency submersible sub-bottom profiler. In this method, we obtained the reflection data of deep-sea sediments near the bottom using a wide-band narrow-beam single transducer and obtained the profile of deep-sea sediments using the reflection compression method. The first sediment layer was extracted according to the layer structure information, and the sound speed of the first sediment layer was directly measured. The transducer feasibility of the high-frequency submersible sub-bottom profiler operating at high pressure in deep sea was verified through high hydrostatic pressure tests in the laboratory. We designed a laboratory reflection compression measurement device to simulate the first layer of deep-sea sediments and verified the effectiveness of the measurement method. This method also was used to process deep-sea sediment data acquired by the Deep-Sea Warrior manned submersible.