The Vibration Reduction Index Kij: Laboratory Measurements for Rigid Junctions and for Junctions with Flexible Interlayers

Abstract

The vibration reduction index Kij expresses the attenuation of the vibrational power flow through a junction. This quantity is important because it determines the contribution of the flanking transmission to the global sound transmission between rooms. It is used in acoustic building prediction models like that proposed in the standard EN 12354. Currently a draft exists to measure the Kij in laboratory. This draft, the prEN 10848, was prepared by the Technical Committee CEN/TC 126 and has been submitted for parallel enquiry. There are also prediction formulae available for the Kij, which are included in Annex E of the standard EN 12354-1 (2000). This article presents the Kij measured in a laboratory according to the draft prEN 10848 and documents an investigation in order to validate them for rigid junctions and junctions with a flexible interlayer. The observations focus on the comprehension and the quantification of the influence of some parameters like the modal overlap factor, the number of modes and the workmanship on the accuracy of the results. Furthermore, an extensive discussion tackles the problem of the determination of the parameter f1 used in the prediction formulae for junctions with flexible interlayers and the effect of the applied load.