ADDRESSING COMPLEXITY IN STRUCTURAL ACOUSTICS - FUZZY STRUCTURE AND EFFECTIVE IMPEDANCE THEORIES

The theory of fuzzy structures (TFS) and effective impedance theories (EIT) are presented as two frameworks for accommodating structural aco ustic complexity, occasioned by incompletely described, small sized st ructural elements appended to a large sized main structure. The presen tation identifies the TFS as part of an extensive literature spanning applications of statistical physics and composite materials. EIT are p resented as renormalizations of a TFS, for estimating precisely descri bed ''smoothed'' measures of the main structure response. The smoothin g applied refers to either a statistical smoothing or a spatial smooth ing. A special class of small scale structural elements, designated as isolated and point connected, is considered in some detail. Thus, two specific types, classified as added mass and added stiffness fuzzy st ructures, are identified and shown to result in fundamentally differen t EIT. The issue of an enhanced dissipation of the vibrations of a lar ge scale main structure by the attachment of small scale detail struct ures is investigated and related to previous studies. Several outstand ing research issues are identified. (C) 1997 Elsevier Science Ltd.