Shallow water ocean reverberation data analysis and extraction of seafloor geo-acoustic parameters below 4KHz

This dissertation presents some unique analysis and processing procedures and describes new results from measurements of seafloor reverberation using a horizontal line array. A primary goal of this research is to use the reverberation data to usefully characterize the ocean bottom.; An original aspect of this work is the analysis of reverberation data from three recent experiments performed jointly with SACLANTCEN and DRDC. Sources were monostatic SUS charges and coherent pulses. The receivers were horizontal arrays. Data were analyzed in bands from 80 to 4000 Hz. Highlights of the reverberant returns are discussed. One site is a relatively flat, heavily sedimented area, but with a rocky ridge to the east. The second area is known to have benign surface morphology but contains many buried river channels. Using coherent bistatic and monostatic sources near 400 Hz, many small strong clutter returns were found in this area which seem to correlate with the location of buried river channels. Differences in reverberation characteristics between SUS and coherent pulse results are discussed. Some statistical characterization of the observed clutter is also presented.; A principal objective of this work is to extract useful geo-acoustic and bottom scattering parameters that apply over a large ocean area. An original aspect of this work is the design and implementation of an inverse method using towed array data to accomplish that goal. For each data set, a simulated annealing algorithm is used together with the Generic Sonar Model. After automatically adjusting bottom loss and scattering strength, good agreement is achieved between the diffuse reverberation data and model predictions in relatively flat areas. Model/data differences are generally correlated with bottom scattering features. Since reverberation from SUS typically lasts 10–40 s or more, extracted parameters apply over wide areas. Local bottom loss and backscattering measurements were made by Holland in these areas. A comparison of geo-acoustic models obtained with his method and with this one was quite good. Further, a comparison of transmission loss predicted with Turgut's local inverse method and transmission loss predicted with the method presented here, gave answers that were usually within 3 dB of each other.