잔향음을 이용한 지음향 인자 역산

Abstract

In this dissertation a primary goal of this paper is to use the 8 kHz bottom reverberation data to characterize the sediment properties using mid-frequency bottom reverberation model. This work presents some analysis and processing procedure from measurements of bottom reverberation using a single hydrophone. Analysis is presented on the bottom reverberation data from experiment performed in September 2007 in shallow water 16 m of deep, off the coast of Ando in the south of Korea. The omni-directional source and receiver were set near enough to the bottom to obtain the bottom reverberation signal without surface interaction. The experimental site was relatively flat that the bottom slope is 1.5°. The measured bottom reverberation signal is used to verify the forward reverberation model for geoacoustic parameter inversion and the measured backscattering strength from the bottom signals are compared with the APL-UW bottom scattering model. The optimization technique is based on Monte Carlo method and mid-frequency bottom reverberation model is used as the forward model for bottom reverberation. The mid-frequency bottom reverberation is modeled based on the Gaussian Ray Bundle which is ray based model with APL-UW bottom scattering model. The sensitivity of geoacoustic parameters is studied to understand the complexity of the problem and the result shows that sound speed and volume parameter is more sensitive than others. The objective function is a sum of a mean square error between the measured bottom reverberation data and the mid-frequency reverberation model run. In this work, a data-model comparison is used to address following questions; 1. Suitability of APL-UW bottom scattering model for mid-frequency reverberation. 2. Suitability of mid-frequency reverberation model which is consisted of GRAB and APL-UW model for inversion of geoacoustic parameters. 3. How sensitively does the mid frequency reverberation model results depend on the geoacoustic parameters and characterize the parameters (sediment volume, surface roughness et al.)?