# Structural Acoustics

Structural acoustics is the study of the vibration and subsequent
acoustic radiation from structures. Examples of such structures include
models such as beams, plates, shells, as well as more realistic
structures such as automobile components, airplane interiors, and
submarine hulls.

** Fuzzy Structures **

Dr. Sparrow's current research in structural acoustics deals with
a topic called fuzzy structures.
Fuzzy structures are not related to fuzzy sets, a separate
important area. Originally developed at ONERA in
France by Christian Soize, fuzzy structures is the study of large
dynamical systems, such as entire ships or airplanes, in which not
all of the dynamical components can be described with certainty.
A number of models for fuzzy structures now exist.
Any of these fuzzy structures models can be straightforwardly included
in conventional finite element representations for a structure.

The Soize fuzzy structures model assumes that a large number of
probabilistic one degree of freedom oscillators are ''painted'' over
an area of the structure that is well understood. Here is an
example of the dynamical behavior of a normal one degree of freedom
oscillator and an identical oscillator except in having uncertainty
in its mass:

Normal:

Fuzzy:

These are frequency response plots, impedance in Ns/m versus frequency
in rad/s, for a one degree of freedom oscillator. The normal plot
has no uncertainty, and the fuzzy plot has all
parameters the same except for a plus or minus 20 percent
uncertainty in the oscillator's mass. This research was
undertaken in collaboration with Daniel A. Russell and
Judith L. Rochat.

This research was funded by the Office of Naval Research.

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© 1995, 1996, Victor W. Sparrow.

Most recent update: 8/12/97

For more information contact
sparrow@helmholtz.acs.psu.edu.