Studies On Robust Matched Field Inversion And Noise Suppression

This dissertation studies mainly the inversion of ocean environmental parameters in shallow water and the suppression of sea-surface noise interferences in mismatch environment by Matched Field Processing (MFP). Acoustic field modeling using Parabolic Equation method is analyzed, a global optimization algorithm is developed, the uncertainty analysis of matched field inversion is conducted, and the surface interference suppression algorithm in mismatch environment is obtained. The main contributions are as follows:(1) The global optimization algorithm applied matched field inversion is developed based on generalized neighboring region theory. The optimization algorithms presently applied to matched field inversion are compared. In consideration of a Benchmark problem, two basal algorithms, i.e. Differential Evolution algorithm and Down Hill Simplex algorithm, are selected and a hybrid optimization algorithm based on the basal algorithms is proposed. The structure and performance parameters of the hybrid optimization algorithm are deduced, and a flow chart of the algorithm based on generalized neighboring region theory is shown. Using Matched field inversion Benchmark problem a comparison has been made between the hybrid optimization algorithm, it is called Down Hill Simplex Differential Evolution algorithm, and the basal algorithms. The results indicate that hybrid optimization algorithm is more effective.(2) The uncertainty problem of the matched inversion is investigated using Bayesian statistics and decision theory. The Full Bayesian approach and Empirical Bayesian approach are introduced and the computational complexity is discussed. Qualitative and quantitative analysis for the inversion is performed in low and high dimensional parameter space using the benchmark problem. For the low dimensional case the Full Bayesian approach is adopted for validating the computational model using different signal to noise rate and inversion frequency. For the high dimensional case the computational complexity problem is considered and an algorithm which calculates the inversion uncertainty is developed based on the optimization algorithm.(3) Using experimental data in the Mediterranean Sea the developed algorithms are validated. According to the ocean environment, range dependent inversion is conducted and the results are analyzed.