### ASA 127th Meeting M.I.T. 1994 June 6-10

## 3pSAa10. The radiation modes of baffled finite plates.

**Noelle Currey
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Kenneth A. Cunefare
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*The George W. Woodruff School of Mech. Eng., Georgia Inst. of Technol.,
Atlanta, GA 30332-0405
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The modal-style approach for representing the exterior radiation
characteristics of structures generally seeks to find a set of orthogonal
functions, or acoustic modes, that diagonalize a radiation operator in the
exterior domain of the structure. The choice of basis functions for the modal
representation is arbitrary, though use of the natural modes of structural
vibration tends to provide some physical insight. The acoustic modes are found
through an eigen analysis or singular value decomposition analysis of the
radiation operator. The eigenvalue or singular value associated with a given
mode is directly proportional to the radiation efficiency of that mode. The
dependency of the radiation efficiencies and mode shapes on the number of
degrees of freedom permitted in the derivation of the radiation operator is
investigated for a baffled finite rectangular plate. The accuracy of the
acoustic modal representation depends on the number of degrees of freedom
permitted in the derivation of the radiation operator, with the least efficient
modes converging slowest. Further, the rate of convergence is dependent on the
particular basis function selection. The convergence behavior has significant
impact on those applications of the exterior acoustic modal approach that seek
to exploit the least efficient modes. [Work supported by NASA GSRP program.]