Modeling acoustic target response by component

Abstract

The scattered acoustic response of underwater objects due to active interrogation has been studied for decades for use in detection and classification applications. As a means of detection, fielded applications date back nearly a hundred years. However, use of responses for robust automated classification has lagged behind, particularly when the internal structure of the objects is of key importance and when the objects may be partially or fully buried. Analytic solutions for simple geometries have provided much understanding of certain physical mechanisms, but transfer to complex structures of practical importance has proven difficult. In recent decades, finite element (FE) modeling has provided a method of accurate simulation of many structures previously considered intractable. However, simulation of such complex objects produces equally complex returns, with the result that the models are often simply considered as a "black box" where the physical interpretation of the response components is tenuous at best. Thus the state of the art is still short of a method for development of robust classification systems for complex objects based on the physics of the objects of interest and the varied conditions under which they may be found. This paper introduces an effort to use FE techniques to simulate individual components of a return by "turning off" most aspects of the physics and allowing the researcher to isolate one mechanism at a time. The goal is a true physical understanding of the complete response, a physically justifiable feature set for classification, and a much simpler path to environmental robustness.

Time and frequency constrained sonar signal design for optimal detection of elastic objects

“…[39][40][41][42] The output of the FE models can then satisfy the requirement for target impulse responses when the target of interest is far more complex than the simple example given in our simulation. Another recent development compares a number of analytical and experimental methods for generating target responses for the purpose of populating a target response database.…”