Isolation of the Spectrograms and Rosettes of Insonified Sets of Submerged, Concentric, Thin Shells

[+] Author and Article Information
G. C. Gaunaurd

Naval Surface Warfare Center, White Oak Detachment (R-34), Research & Technology Department, Silver Spring, MD 20903-5640

A. Akay

Carnegie Mellon University, Department of Mechanical Engineering, Pittsburgh, PA 15213

J. Vib. Acoust 116(4), 573-577 (Oct 01, 1994) (5 pages) doi:10.1115/1.2930466 History: Received January 01, 1993; Revised October 01, 1993; Online June 17, 2008


The resonance features present, and observable, in the form-functions of submerged, fluid-filled, elastic, thin shells, usually appear combined with smooth, undesirable, background components that tend to obscure them. In order to isolate these features in the frequency domain, at fixed angles of observation, (i.e., the “spectograms”), or in the angular domain, at selected frequencies (i.e., the “rosette” patterns), one usually attempts to suppress the background components by subtracting “suitable” background coefficients. Since the rigid/soft background coefficients of solid elastic bodies/cavities in solids yield unsatisfactory results for thin shells, various other background coefficients have been tried with various levels of success. We present here a more general scattering formulation, valid for many concentric shells, that permits the isolation of these resonance features without having to subtract any type of background coefficients. This resonance feature extraction is achieved either conceptually, or physically, filling the various spaces in between the various concentric shells, with the same fluid present in the outer ambient medium. The extraction of these echo-features is crucial for purposes of active classification by sonar.

Copyright © 1994 by The American Society of Mechanical Engineers
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