Approaches for room- and vibro-acoustical applications based on Integral Transform Methods

At LMSSC, Cnam, Paris, October 24th 2012, 14 p.m.

Martin Buchschmid
Assistant lecturer, Chair of Structural Mechanics, Institute of Cross-Cutting Technologies,
Faculty of Civil Engineering and Geodesy, Technische Universität München (TUM), Germany

In many different fields of engineering, like automotive industry or civil engineering, room- as well as vibro-acoustical tasks are of interest. The sound field in acoustic cavities caused by structural vibrations or internal sound sources has to be predicted in order to design either the acoustic volume by placing acoustic elements like reflectors or absorbers (passive absorbers or plate resonators) or to change the characteristics of the transmission system by modifying impedances for instance.

Models for the Fluid Structure Interaction (FSI) based on Integral Transform Methods (ITM) can be used for this purpose. Considering the coupled problem in the wavenumber-frequency domain radiated sound due to finite vibrating plate-like structures can be predicted under free-field conditions very efficiently at the basis velocity patterns, which can be obtained from FEM-computations or measurements for instance. For modeling acoustic cavities with absorptive boundary conditions e.g. located at the interior claddings, a model reduction method, based on a Component Mode Synthesis (CMS), can be applied in order to reduce the number of degrees of freedom and therefore the numerical effort. The cavity boundary conditions, e.g. compound absorbers made of homogeneous plates and porous foams, can be modeled using ITM in combination with material models for porous foams like the Theory of Porous Media (TPM). Defining the coupling-condition in terms of impedances, which are computed in the wavenumber-frequency domain the absorptive structure can be considered both, via impedances out of measurements or numerical simulations. In order to enable simulations for realistic structures, the acoustic volume can be modeled with numerical methods like Spectral Finite Elements (SFEM) and coupled to the absorptive component.

In the scope of this talk the methods mentioned above are discussed in detail focusing on the mechanical models as well as on the material descriptions. The application of these approaches is presented with the help of academic and practical examples.

Laboratoire de Mécanique des Structures et des Systèmes Couplés - LMSSC