Conference_programme: 17: Building acoustics

Lecture: Validation of structure-borne sound prediction methods

Author(s): Nagy Attila Balazs, Fiala Peter

Summary:
Conventional Boundary Element Method (BEM) and acoustical Finite Element Method (FEM) can be used for predicting structure-borne sound provided that velocity\ndistribution along the walls is known in sufficient details, but these are computationally demanding and therefore are mainly used in the lower frequency range in practice. There exist also new or modified, hybrid methods that try to combine efficiency and accuracy: Spectral Finite Element Method (S-FEM), Wave Based Method (WBM) and the Fast Multipole BEM (FM-BEM). Beside these a Rayleigh integral based method for structure-borne sound calculations was introduced earlier as a possible alternative: this method uses mirror-image sources in order to determine the modified Green's function that describes the reverberant sound field. In this paper we evaluate accuracy and applicability of the Rayleigh-based method by comparing it to S-FEM simulations and to measurement results. \n\nFor this purpose mesurements were carried out on a brick wall built into a test facility for sound insulation measurements: the wall was excited by airborne sound on one side, and vibration velocity as well as radiated sound pressure in several points were measured on the receiver side. This well defined radiation problem (no flanking transmission) was re-created in model space.\nThe simulations investigate the frequency dependent effect of the spatial resolution of vibration velocity data: calculations spread from single point vibration input up to a detailed vibration distribution along the walls. The effect of reflection order on the accuracy of Rayleigh-based calculations is also examined. Finally, a simplification of the Rayleigh-based method is introduced and its applicability is discussed. \n

Corresponding author

Name: Mr Attila Balazs Nagy

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Country: Hungary