The research project AkuLite ended 30th April this year and AcuWood will finish the 30th of September and almost four years of acoustic research with a focus on acoustics and vibrations in multi-storey residential buildings with light weight structures terminates thereby. However this is not the same thing as all activity ceases in lightweight acoustic and vibration construction research. High activity has been undertaken during late 2012 and beginning of 2013 in order to set up projects that can continue after AkuLite and AcuWood. Despite great progress in both projects and a clearly elevated level of knowledge everything is, of course, not yet solved. However, the goals are fulfilled and now it is time to enter the next phase. AkuLite and AcuWood have both been an exciting journey with a great number of dedicated participants involved. The projects consisted of a total of ten institutions / research practitioners and about 35 to 45 different industries throughout Europe. The main focus for the projects were to deliver new proposals for evaluation measures regarding sound insulation in order to provide right target values for the construction industry when they develop new building systems for the future.

This report is a summary of the presentations, discussions and conclusions from an international workshop on “Acoustics and Vibration in Wood Construction”. The workshop was organised by Skogsindustrierna (Swedish Forest Industries Federation) in co-operation with CEI-Bois Building With Wood. The report has been compiled by Klas Hagberg, WSP. The report contains a short summary of the presentations held during the workshop as well as a summary of the group discussions. The report also concludes that, from the industry’s point of view, the topic “development of structural solutions” should have the highest priority in upcoming research calls and projects.

In the recently finished research projects, AkuLite and AcuWood, it is clearly stated that low frequencies should be considered far more, prior to design new wooden structural building system. Lower than 50 Hz is preferable, and the most annoying frequencies appear between 20 and 50 Hz. However, it is still a long way to go in order to convince acousticians, the entire global industry and authorities that these frequencies have to be considered in order to build wooden structures which are experienced by the habitants as equally good as heavy structures. To "save" the industry, a lower limit of at least 50 Hz at least for impact sound should be mandatory in the near future globally, in spite of the fact that the new standard ISO 16717 will not be reality. This paper describes the main reasons why it is needed to include these low frequencies in residential buildings. It describes different constructions and their appearance due to low frequency impact sound transmission. The paper comprises some examples designed to fulfill the Swedish requirements, which equals Ln,Tw and Ln,Tw+CI,50-2500 ≤ 56 dB between dwellings. It comprises also a discussion regarding optimizing constructions for various uses, e.g. different types of housing.

After four years of research with a focus on human experience regarding acoustics and vibrations in multi storey residential buildings (AkuLite and AcuWood), it is time for the next very important step for the wooden industry, to catch up regarding prediction models. The wooden industry and their market shares are increasing. One important reason is increased requirements regarding sustainability in the building sector. Long term sustainability implies an acoustic comfort that mirrors the perception of the humans using the buildings, but it also requires calculation models available in order to predict the final acoustic and vibrational quality of the buildings. To promote this development at least two new projects have been set up during the autumn of 2013 in Europe, started immediately after AcuWood and AkuLite. One Swedish project managed by Luleá Technical University with the aim to continue to develop and refine rating methods to fit all structural materials and one big European consortium is setup within WoodWisdom-Net+ programme in order to develop structural prediction models for wooden constructions. The models should be integrated in the CEN and ISO standards to extend the use of these standard series in order to cover also wooden structures in the future. The models will be developed in a full frequency range in order to create the basisfor calculating vibration criteria and sound insulation single numbers according to new proposals in the recently finished projects, adapted to human experience.

Many multifamily houses are produced by small or medium size enterprises (SME's). These developers produce a substantial number of residential units per year. They have normally limited resources and need to have easy access to cost - effective structural solutions. Typical buildings comprise two storeys and four to eight flats. Due to costs and production efficiency these buildings are produced in light material, mainly wood. Each building is unique and the limited size of each project means that it cannot defray costs to adapt each building of interest, to available building system on the market. Instead, the builders need to have access to; 1. structural design guidelines to secure dimensions and acoustic performance; 2. assembly information regarding details; 3. process guidance to minimize risk exposure, secure the final result. This paper describes a typical design procedure and final results, for a small two - storey building comprising six residential units. The procedure fits to an SME, with limited resources for technical development. The building was designed and erected presupposing that everything has to be built "on site". This paper is also an introduction to a new guidance book, being prepared within the Swedish research project AkuLite.

There is little data available of low frequency impact sound response of light weight wooden buildings. The ISO 140-7, 717-2 standards normally used of impact sound is limited down to 50 Hz. The response in low frequency area is of interest for human comfort. In the present work low-frequency impact sound measurements were carried out in two modern office buildings with lightweight timber frame. The purpose was to assess the levels of impact sound transmission below 50 Hz in these construction types. The low frequency impact sound levels are compared to the higher. Both the tapping machine and the impact ball are used for excitation. It is seen that the present constructions have their highest levels below or close to 50 Hz when excited by the impact ball. From the office rooms sharing joist floor with corridor there is seen increased levels of low frequency impact sound. Up to 10-15 dB higher impact sound was detected compared to room with joist floor separated from corridor.

Cracks in glulam beams can reduce their strength, depending on the crack's depth, length, and location and can also be a passage for the accumulation of water and dirt. To avoid cracks, the relationship between cracks (area of cracks, mm2) and annual-ring orientation in glulam beams of spruce (Picea abies), and pine (Pinus sylvestris) with different dimensions and surface treatments was investigated using RGB images of the surface and tomography images of the cross-sections. Image processing was used to measure characteristics visible in the photos such as crack area and lamella position in the beam. Combination of lamellas in lay up was measured from computer tomography images. Four types of combinations were defined; type 1 (pith side facing outward), types 2 and 3 (pith to the same side), and type 4 (pith sides meet pith side). It was found that the area close to the glue line in the lamellas in combination type 4 is the most subject to cracking, whereas combinations of type 1 show the highest resistance to cracking. This means that type 4 should not be used in glulam beams, because the lamellas shrink apart from each other causing stresses and resulting cracks.