An energy method for midfrequency and low modal overlap

Abstract

Some new work has been done on the use of discrete modes to improve the spatial and spectral variance of statistical energy analysis (SEA) estimates of structure-borne noise at ‘‘midfrequencies.’’ For any given frequency band one can partition the subsystem into two groups—high and low modal overlap. Phase-correlated responses across junctions of low modal overlap subsystems (e.g., beams) suggest that at low to midfrequencies, their response is better described by a ‘‘global’’ mode set. These modes are generally few in number and can be estimated with numerical eigensolvers by assuming that the separate set of high modal overlap subsystems contributes only nonresonant stiffness or mass. Coupling loss factors between high and low modal overlap subsystems defined in this new way can be estimated using a generalized Green’s-function form [R. S. Langley, J. Sound Vib. 141, 207–219 (1990)]. Results are presented for the sharing of energy between a low and high modal overlap beam network, with comparison to an ‘‘exact’’ dynamic stiffness solution and SEA. There is a very satisfactory improvement in spectral variance at midfrequencies. [Work supported by RESOUND Consortium.]