The vibration reduction index K ij 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 K ij 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 K ij, which are included in Annex E of the standard EN 12354-1 (2000). This article presents the K ij 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 f l used in the prediction formulae for junctions with flexible interlayers and the effect of the applied load.
The prediction of the reduction of impact sound pressure level ΔL according to annex C of the standard ISO 12354-2 gives an acceptable estimation of the floating floor's performance for thin resilient layers. However, the performance is often largely overestimated for thick resilient
layers or for resilient layers combined with thermal layers. One reason for this is that the simplified model doesn't account for the thickness resonances in the underlays which can greatly affect ΔL. This is confirmed by comparing finite element and transfer matrix method simulations
with experimental results. This paper establishes the mechanisms leading to the development of these resonance waves and provides some guidelines to estimate their negative effects on the ΔL.
An important brick manufacturer in partnership with the BBRI has succeeded to propose efficient acoustic solutions for this kind of lightweight materials by treating the flanking transmission using flexible interlayers at junctions and foundations. A large measurement survey has been carried out to study the efficiency of the resilient joint and to provide a prediction model on airborne sound insulation in brickwork constructions. The prediction model used is based on the standard 12354-1 but was adapted in order to take into account higher orders for the flanking transmission paths. This adapted model thus allowed studying different applications of the flexible joint and their contribution to the improvement of the global sound insulation. This paper presents a discussion on the calculation model, the input data and some early results.
An extensive measurement survey of timber floor constructions has been carried out by the acoustics laboratory of the Belgian Building Research Institute [1]. The basis of this study was the airborne and structure-borne sound insulation measured on a bare joist floor with OSB (Oriented Strand Board) sub floor. By adding different floor toppings and gypsum board ceilings to the basic floor construction, gradual improvements were recorded. A large number of floors are evaluated in the laboratory and formed a database for parametric studies. Improvements due to cavity absorption, floating floors and suspended ceilings were quantified and ranked by effectiveness. Measurement results revealed remarkable differences between floating floor systems. In addition, sound insulation measurements have been performed on joist floors with concrete toppings. The so-called mixed concrete-timber floors provide a higher mechanical resistance. The effect of the bonding and topping type on the airborne and structure borne sound insulation has been examined in the laboratory. The results of this additional research are briefly compared to traditional floor systems and compared with the (future) Belgian standard values. An overall evaluation of the acoustic relevance of timber floor partitions in and between dwellings is also made.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.