Fundamental Structural-Acoustic Idealizations for Structures with Fuzzy Internals

[+] Author and Article Information
A. D. Pierce

Department of Aerospace and Mechanical Engineering, Boston University, 110 Cummington Street, Boston, MA 02215

V. W. Sparrow, D. A. Russell

157 Hammond Building, Pennsylvania State University, University Park, PA 16802

J. Vib. Acoust 117(3A), 339-348 (Jul 01, 1995) (10 pages) doi:10.1115/1.2874456 History: Received June 01, 1993; Online February 26, 2008


Fundamental issues relative to structural vibration and to scattering of sound from structures with imprecisely known internals are explored, with the master structure taken as a rectangular plate in a rigid baffle, which faces an unbounded fluid medium on the external side. On the internal side is a fuzzy structure, consisting of a random array of point-attached spring-mass systems. The theory predicts that the fuzzy internal structure can be approximated by a statistical average in which the only relevant property is a function m F (Ω) which gives a smoothed-out total mass, per unit plate area, of all those attached oscillators which have their natural frequencies less than a given value Ω. The theory also predicts that the exact value of the damping in the fuzzy structure is of little importance, because the structure, even in the limit of zero damping, actually absorbs energy with an apparent frequency-dependent damping constant proportional to dm F (W)/dω incorporated into the dynamical description of the master structure. A small finite value of damping within the internals will cause little appreciable change to this limiting value.

Copyright © 1995 by The American Society of Mechanical Engineers
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