### ASA 125th Meeting Ottawa 1993 May

## 4pSA7. Structural acoustic modeling using a new high accuracy acoustic
infinite element.

**David S. Burnett
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*Rm. 1A-254, AT&T Bell Labs., Whippany, NJ 07981
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This new 3-D time-harmonic acoustic infinite element uses a truncated form
of the exact asymptotic series solution for general scattered and/or radiated
fields, providing an accurate approximation all the way to infinity. The
infinite element and a companion fluid--structure coupling element have
symmetric matrices that fit seamlessly into any structural finite element code,
providing a structural acoustic capability as versatile and powerful as the
structural code itself. Most important, this approach is several orders of
magnitude faster, for the same accuracy, than the traditional and almost
universally used boundary element method (BEM) for the acoustics, i.e., the
surface Helmholtz integral equation, which the author also developed and used
for several years. The reason is that the bandwidth of the coupled system
equations is much smaller for infinite elements (being a domain method) than
for the BEM. Experience with both methods has revealed that the severe
computational inefficiency of the BEM limits practical problems to low
frequencies and simple structures, whereas this infinite element approach can
handle the full range of frequencies and structural complexities that are
encountered in purely structural analyses, at little additional cost.