Bart Ingelaere

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

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.

Acoustic Comfort In Timber Frame Dwellings

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.

Laboratory Sound Insulation Measurements of Improved Timber Floor Constructions: A Parametric Survey

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.

Innovative building systems to improve the acoustical quality in lightweight masonry constructions: Application of resilient joints at junctions ‐ PART 1: Analysis of the experimental results

The more severe acoustic requirements imposed by the new Belgian standard for dwellings are a real challenge for the building professionals (architects, contractors, building elements manufacturers and suppliers, œ) and more particularly for the market of lightweight materials. An important brick producer in partnership with the BBRI has succeeded to propose efficient acoustic solutions for these kinds of materials by treating in particular the flanking transmission. Indeed, to obtain high sound insulations, the structural transmission paths of noise through the flanking walls cannot be neglected any more. By the application of resilient rubber interlayers at the junctions, these transmission paths are nearly eliminated. A large number of measurements was carried out in order to study in detail the effect of these flexible joints on the sound transmission. These measurements were made in a specially designed laboratory where vibration reduction indexes can be measured for all types of connections and for ...

New acoustic solutions for cross laminated timber based buildings

Cross laminated timber is becoming a popular building material for the construction of multifamily dwellings, offices, hotels, etc. The acoustic challenges are important: in contrast to light weight timber frame constructions, it is far more sensitive to flanking transmission and its equally relatively light weight and orthotropic character in comparison with traditional heavy stone requires special solutions for the direct airborne and impact sound insulation. The paper presents a new, special, and patented building system that almost annihilates flanking transmission and will detail optimized low frequency sound insulation solutions for floors.

Numerical study on the repeatability and reproducibility of laboratory building acoustic measurements

An important issue in building acoustics is the significant variability in laboratory test results that numerous round robin tests have indicated. The current wish to include the frequency bands 50-80 Hz in the procedures to determine single-number quantities has prompted new discussions. In this paper, wave based models are used to numerically investigate the fundamental repeatability and reproducibility. Regarding sound insulation measurements, both the pressure method (ISO 10140-2) and the intensity method (ISO 15186-1 and ISO 15186-3) are investigated in the frequency range 50-200 Hz. Flanking transmission measurements (ISO 10848) are also studied. The investigation includes the repeatability of the different measurement procedures, which depends on the influence of the source and receiver positions. The reproducibility in different test facilities is studied by looking at the influence of geometrical parameters like room and plate dimensions. Increasing the number of source or receiver positions has ...

The repeatability and reproducibility of laboratory building acoustic measurements: Numerical study

An important issue in building acoustics is the significant variability in laboratory test results that numerous round robin tests have indicated. The current wish to include the frequency bands 50-80 Hz in the procedures to determine single-number quantities has prompted new discussions. In this paper, wave based models are used to numerically investigate the fundamental repeatability and reproducibility. Regarding sound insulation measurements, both the pressure method (ISO 10140-2) and the intensity method (ISO 15186-1 and ISO 15186-3) are investigated in the frequency range 50-200 Hz. Flanking transmission measurements (ISO 10848) are also studied in a broad frequency range. The investigation includes the repeatability of the different measurement procedures, which depends on the influence of the source and receiver positions. The reproducibility in different test facilities is studied by looking at the influence of geometrical parameters like room and plate dimensions, aperture placement and aperture...

High sound and thermal insulation constructions with dB‐deck

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 <47 dB without a floating floor in experimental setups This solution was developed by a team of the BBRI, KULeuven and CDM for an important producer of hollow floor elements. This technique has now been used for real constructions. The paper presents technical details, the results of the acoustical measurements and the acoustical advantages and diculties met in the construction of this apartment block.

Uncertainties and repeatability of the Reception Plate Method

The Reception Plate Method (RPM) as proposed by CEN/TC126/WG7 in prEN 15657‐1 estimates the structure‐borne sound power injected from a (high mobility) vibrating source into a (low mobility) building structure. In the near future, a round‐robin test is planned to investigate repeatability and reproducibility issues of the RPM. As a preparation of this round‐robin, uncertainties of the RPM are studied using the standard ISO tapping machine, placed on a 4 feet table on a reception plate. The injected power into the reception plate is calculated using different methods. The influence of the source position, accelerometer positions and airborne excitation are investigated, together with repeatability tests. Also, differences in injected power between two different brands of the ISO tapping machine will be studied. Finally, in‐situ installed structure‐borne sound power level will be predicted using prEN 12354‐5 and compared to measurements on a simple building structure.

Survey on the insulation performance of acoustic louvres

Machinery such as compressors, boilers and generators require adequate ventilation and extract. To avoid excessive noise breakout, acoustic louvres are frequently used. These are usually made of tilted hollow metallic blades filled with absorptive materials and perforated at the inside face. This study investigates the important characteristics of common shaped acoustic louvres with regard to sound insulation. First, a market survey on 109 existing acoustic louvres of 24 producers worldwide is made. Second, laboratory measurements of sound insulation on 38 prototypes of 1 m2 acoustic louvres are compared. The influence of several parameters are studied such as louvre depth, blade angle, blade shape, blade thickness, blade spacing, kind of absorptive material, perforation degree, and edge filling.