Vibroacoustic Investigations of Light-Weight Ceilings - Modeling Aspects and Design Guidelines

Regular paper

Martin Buchschmid

Chair of Structural Mechanics - Technische Universität München

Wednesday 3 june, 2015, 14:00 - 14:20

Auditorium 2 (592)

In order to set up guidelines for the design of light-weighted ceilings for timber-constructions, investigations based on both measurements and numerical models have been carried out in the research-project "VibWood" at TU München and HAW Rosenheim. The setup and the calibration of the numerical model of the structure are outlined briefly. A semi-analytical approach for the prediction of radiated sound is presented, which is based on Integral Transform Methods. The method can be applied in the post-processing of a Finite-Element-computation. Thus as a first step the structure, consisting of a timber-slab, a floating-floor and a suspended ceiling, is built up in a Finite-Element-model, where the material properties of wood and the characteristics of the system are considered. The model is parameterized to enable computations with varying geometry and material parameters and calibrated with measurements using model-updating-techniques. The velocity pattern resulting out of the FEM-computation is transformed from the spatial into the wavenumber-domain and from the time into the frequency-domain using Fourier-Transform-Methods. Applying this velocity pattern as a boundary condition to the Helmholtz-Equation, which results out of the Fourier-Transform of the wave equation the wavenumbers responsible for sound radiation are selected and the pressure field in the adjacent acoustic fluid is computed. In the Fourier-domain the radiated sound power can be calculated efficiently out of pressure and velocity. Then the model for the air-cushion in the suspended ceiling is discussed, where a FSI-model for the acoustic fluid and the structure is compared against engineering approaches using simplifications concerning mass distribution and transfer-impedances between the interface-nodes. Finally design-guidelines for light-weighted ceilings, set up in the research-project, are presented in terms of a database containing dimensionless results for different types of ceilings as well as a graphical user interface to provide a user-friendly software environment.

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