Technical Note Potential solutions to improved sound performance of volume based lightweight multi-storey timber buildings Fredrik Ljunggren ⇑ , Anders Ågren Division of Sound and Vibration, Luleå University of Technology, 971 87 Lulea, Sweden article info Article history: Received 5 March 2010 Received in revised form 11 November 2010 Accepted 15 November 2010 Available online 10 December 2010 Keywords: Lightweight Timber Impact sound insulation Building acoustic Floor abstract Lightweight building systems in general suffer from poor sound insulation, especially in the low frequency region. Since no reliable mathematical models that can predict the impact sound pressure level exists, the lightweight building design is to a high extent based upon previous experience and upon mea- surements. A special difficulty is related to experimental measurements since the variation among iden- tical units must not be neglected. A modern volume based lightweight wooden building concept has here been tested by numerous well controlled measurements, in laboratory as well as in more field like con- ditions. The volume construction technique offers new possibilities and challenges to improve sound insulation in light weight timber construction. The main purpose was to investigate how different con- structional solutions in the floor, like plaster board, mineral wool, elastic glue, dividing board, floating floor etc., affect the sound insulation. Many of the tested modifications resulted in only marginally chan- ged impact sound pressure level but parameters that substantially can improve the sound insulation were found in using elastic glue to mount the floor boards, to install extra board layers and to use floating floors. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction A clear trend is observed in the modern timber building trade of today towards industrial manufacturing and prefabrication. Not only does the proportion of factory production compared to on-site manufacturing increase, but so does the degree of prefabrication. The great advantage is that a major part of the prospective building is manufactured indoors at a factory with optimized production technique. This in turn leads to benefits in terms of minimized risk of moisture problem during building, better working environment for the workmen, excellent accuracy to size and shortened produc- tion time at the building yard. Prefabrication also brings potential to a better production economy, as well in terms of working time spared as in terms of reduced material wastage, leading to less expensive tenements. 1.1. Volume based building technique For a volume system, the idea is to construct and manufacture modules which contain floors, walls and ceiling together with elec- trical, heating, water, sanitation and ventilation installations. The system is often used for tenements where each volume typically constitutes a small apartment, one room or a part of a larger living room. Although different levels of completeness can be chosen, it is common that as much of the work as ever possible is performed at the factory. The modules then arrive to the building yard with completed surface layers as well as kitchen- and bathroom fix- tures, i.e. a more or less completed part. To form an entire building, the modules are stacked upon each other with a strip of vibration insulation, a so called elastomer, in between, see Fig. 1. This vibration insulation serves as a flexible coupling between the volumes and is an important factor in order to obtain good vibro-acoustic properties. With a proper design the elastomer can significantly reduce flanking sound- and vibration transmission from one floor to another. A great acoustical advantage is that the floor can be constructed as two separated parts. The upper volume contains the upper part of the floor and the lower volume contains the ceiling, meaning that two rooms, one on top of the other, have absolutely no mechanical contact to each other in vertical direction, except for the boundaries. An example of such a floor-ceiling construction, which also represents the structure used in the experiments, is presented in Fig. 2. When the floor sections are being built, the par- ticle boards are glued and screwed to the glulam beams and the floor plaster boards are in turn glued and/or screwed to the particle boards. The purpose of the plywood flanges coupled to the beams is to carry the stone wool insulation. Parquet or plastic carpets are examples of common floor coverings. To ensure that volumes are 0003-682X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apacoust.2010.11.007 ⇑ Corresponding author. Tel.: +46 920 491286; fax: +46 920 491030. E-mail address: fredrik.ljunggren@ltu.se (F. Ljunggren). Applied Acoustics 72 (2011) 231–240 Contents lists available at ScienceDirect Applied Acoustics journal homepage: www.elsevier.com/locate/apacoust