Compatibility between the calculated and the measured sound insulation of composite building elements

Abstract

The computer model prepared for calculation of sound transmission loss (TL) of multilayered structures by using the impedance approach presented before, has been revised for the finite-size elements by integrating it with the windowing technique. The model is described in this paper and the parametric implementations were performed for the building elements. The results have revealed that the model was found to be rather sensitive against even minor change of the materials' physical characteristics which are employed in the model, such as elasticity modulus, loss factor, flow resistance of porous layer, limiting angle of incidence and element dimensions. The effects of these parameters are all frequency-dependent and mostly around the critical frequency of the layers and at the low frequencies near the first resonance. In order to provide the accuracy of the model in terms of insulation values, the results obtained through a former laboratory study by using ISO 140 (ASTM 90) were compared with the revised and computerized model, F-MULAY. 27 different test specimen with varying constructions, materials and sizes which were measured, were used in the predictions and the frequency domain sound transmission losses and the R<inf>w</inf>(C, C<inf>tr</inf>) ratings were computed. The evaluation of the results has revealed that the conformity is rather high for the single and double elements, especially in large-size and at the frequency range which is important in insulation. There exists no difference in terms of the weighted insulation ratings, however the inconsistency at high frequencies implying a lower insulation for the predicted results, is due to the dip in TL curvature at the critical frequencies of the layers, f<inf>c</inf> and the model has later been corrected with the application of the weighted function according to the incident sound energy varying with the angle of incidence and frequency. © 2013 Elsevier B.V., All rights reserved.