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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.

Timber framework has become the most common construction technique in the world for private dwellings. In Belgium, although masonry construction still constitutes the most important market share, the number of new houses with timber framework increases each year. Unfortunately the acoustic insulation of this construction type compares unfavourably with traditional masonry construction. In order to learn more about acoustic performance of timber framework houses and to compare them to the performance of traditional masonry houses, a measurement survey has been carried out, on fifteen single family dwellings with timber framework or heavyweight wood. This paper presents the results of the in situ measurements. The measurements were of façade sound insulation, sound insulation of the inner walls (horizontally and vertically) and impact noise insulation. Similar measurements also have been carried out on houses made of traditional masonry in order to compare the results. A comparison of the results collected in the laboratory and Belgian comfort criteria are also presented. Finally, results of acoustic tests in a multi-family timber construction are presented. The weaknesses of construction techniques observed during the study are discussed.

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.

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.

The new Belgian requirements demand DnT,w⩾58 dB and L'nT,w⩽50 dB between apartments for enhanced acoustic comfort. At the same time the Energy Performance Regulations impose strict requirements for the thermal insulation between apartments. Higher demands on sound insulation can be realized in practice by using higher surface weights for walls and floors and by applying failure free floating floors. However requiring higher weights for floors is in contradiction with the technique of concrete hollow floor elements. A thermal and acoustical solution was found in the development of dB‐deck, a prefab double floor element with intermediate supporting elastic pads, cutting structural vibration paths between superposed apartments. In combination with double walls without anchors (allowing for a high sound reduction index and no structural transmission in the horizontal sense), this construction technique allowed for DnT,w>63 dB and L'nT,w

An important brick manufacturer in partnership with the BBRI has suc‐ceeded 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 campaign 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 to study 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.