A sediment imaging system using acoustic tomographic techniques

An acoustic imaging system has been developed to characterize both horizontal and vertical variability of the sound speed structure of the sediment. The system consists of an array of needle-like probes, approximately 1 meter in length, that may be easily pressed into the sediment. Each probe contains a 20 element line array of acoustic transducers. Acoustic travel time is precisely measured between all combinations of transducers, thus creating a well saturated web of raypaths through the imaging volume. By using inversion techniques, this data may be used to create an image of the sound speed structure of the sediment within the array. The sound speed structure may then be used to determine various material properties of the sample. This paper presents a detailed description of the system that was developed at Woods Hole Oceanographic Institution in 1996. The transducer design, electronics design and mechanical design issues will be discussed. Data will be presented from sea trials performed in 1996, when the system was first tested in Woods Hole, MA.