### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 1pNS3. Developing acoustic models for boundary and finite element methods.

**James T. Browell
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*Software Support, Automated Anal. Corp., 2805 S. Industrial, Ste. 100, Ann
Arbor, MI 48104
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The software needed to develop meshes for acoustic boundary element methods
(BEMs) and finite element methods (FEMs) are the ones commercially available for
structural finite element codes. However, creating a mesh is only the first step
to acoustic model development. The analyst must also consider meshing guidelines
required and simplifying assumptions allowed by the various solution methods.
The density of acoustic analysis meshes is primarily defined by the geometry of
the domain boundary and the maximum frequency of the analysis. Accurately
describing the distribution of boundary conditions and coupling interfaces also
plays a role. While BEMs have distinct modeling advantages over FEMs, BEMs have
specialized modeling requirements. In addition, BEM requires the creation of
data recovery meshes to display results, because the surface of the model is not
usually the point of interest. Simplifying assumptions are made in acoustic
analyses to decrease the time for model development. For example, symmetry is
used to simplify a problem. In addition, assumptions are made to simulate fully
reflective or pressure release infinite planes, such as highways or ponds,
sources are used to represent excitation boundary conditions in the far field,
and acoustic damping is considered as surface impedance or complex speed of
sound.