Ivan Bosmans

Diffuse transmission of structure-borne sound at periodic junctions of semi-infinite plates

Vibration attenuation at junctions of point connected plates is an important aspect of structure-borne sound transmission in many realistic structures. The vibrational response of point connected plates can be predicted using statistical energy analysis (SEA), where coupling loss factors are calculated based on mobility formulations. However, in the process of deriving the coupling loss factors for point connected systems, a number of assumptions and simplifications were introduced. In this paper, a more advanced calculation model, based on a wave approach for elastically coupled semi-infinite plates, is presented. Local rigid connections are modeled using an elastic interlayer characterized by a space-dependent stiffness. Periodic boundary conditions are assumed at the junction and the plate response is described using a Fourier decomposition technique. Calculation results obtained for two different junction geometries demonstrate the influence of the distance between the point connections on the structu...

Sound absorption of stretched ceilings with an impervious synthetic membrane

The sound absorption of stretched ceilings consisting of an impervious PVC membrane is investigated. A theoretical model is used to predict the random incidence sound absorption, and results are compared with the results of an experimental setup in a reverberation chamber. The sound absorption coefficient is estimated using a general model for the acoustic transmission and absorption of a multi-layered structure. Measurements have been performed for several cavity depths, and for two different sound absorbing materials in the cavity. Both theory and experiment showed that the combination of the impervious foil and the cavity behaves as a resonant system. The sound absorption varies strongly with frequency and is highly dependent on the characteristics and the position of the sound absorbing material in the cavity.

In situ measurement of the stiffness properties of building components

Abstract In this paper three methods for measuring the stiffness properties of beams and plates in the frequency range from 100 Hz to 4 kHz are presented. The first technique determines the bending wave velocity in acoustically thin beams and is based on a finite difference approximation of the bending wavenumber. The other two methods involve the measurement of the plate impulse response in two points in order to determine the bending wave velocity in acoustically thin as well as acoustically thick plates. Both these methods are convenient to estimate the angle dependent wavespeed of orthotropic plates. The three measurement methods have been verified by experiments on beams and plates of various materials and thicknesses.

Sound‐absorption properties of suspended ceilings with plastic foils

Suspended ceilings using plastic foils can be used as wall or ceiling finishing systems. The cavity behind the foil (plenum) is used for hiding technical appliances. Without sound‐absorbing material in the plenum, the absorption coefficient of the suspended ceiling can be very low, and even with absorbing material in the cavity, the presence of the membrane can seriously degrade the acoustic performance. The sound‐absorption properties of suspended ceilings using a plastic impervious membrane are investigated theoretically and experimentally. The sound absorption coefficient has been modeled using a general model for the acoustic transmission and absorption of a multilayered structure. Measurements have been performed in a reverberant room using different sound‐absorbing materials in the cavity. Due to the impervious foil, the structure behaves as a resonant system. The different physical mechanisms of these resonances will be highlighted and simple equations to estimate the resonance frequencies are put ...

The use of semianalytical calculation models to verify SEA predictions of flanking transmission in building structures

The prediction of structure‐borne sound transmission between coupled plates represents a key aspect when studying sound transmission in buildings, since vibrational energy flow between walls and floors leads to the existence of flanking paths. The resulting flanking transmission can be assessed theoretically using statistical energy analysis (SEA). In this method, the coupling between plates is usually estimated based on the wave approach for the corresponding semi‐infinite plates. For a specific type of junction, one might consider verifying the predictive performance of SEA experimentally on an isolated plate junction. However, possible discrepancies between measured and predicted data can result either from the failure of the calculation model for the semi‐infinite plates, or by the violation of the basic SEA assumptions. In this paper, a semianalytical calculation model based on a modal summation approach for finite‐sized plates is proposed to determine the source of the prediction error. For this pur...