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  • 1.
    Blomqvist, Lars
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Jarnerö, Kirsi
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Framtidens resurseffektiva KL-trä – en spaning2023Report (Other academic)
    Abstract [en]

    Cross-laminated timber (CLT) for house construction is a product that was developed in Central Europe in the mid-1990s. The purpose of this study is to collaboratively explore proposals for how a more efficient CLT product can be designed for the future. The goal is to produce a basis for development and generate a consensus around the issue. There is an awareness of the environmental factors that affect design with CLT. In addition, an increased demand for wood in the building sector has resulted in a dynamic mindset to replace concrete with CLT. Increased use of forest raw materials, global warming and reduced access via restrictions in forestry raise questions such as: What raw materials will we have in the future? Which tree species will be available? How large will the supply of raw materials be? The resulting material has been analysed based on the different perspectives represented by the stakeholder groups in the value chain for building with CLT. The report concludes with project ideas that emerged during the work on the feasibility study.

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    Framtidens resurseffektiva KL-trä – en spaning
  • 2.
    Bolmsvik, Åsa
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Olsson, Jörgen
    SP Trä.
    Model calibration of wooden structure assemblies: using EMA and FEA2014In: World Conference on Timber Engineering (WCTE), Quebec City, 10-14 August, 2014, 2014Conference paper (Refereed)
    Abstract [en]

    To predict and possibly, when needed to fulfil regularizations or other requirements, change the design to lower the impact sound transmission in light weight buildings prior to building, dynamically representative calculation models of assemblies are out most important. The quality of such models depends on the descriptions of the components themselves but also of the representation of the junction connecting the building components together. The material properties of commonly used components have a documented spread in literature. Therefore, to validate junction models, the dynamics of the assembly components at hand have to be known. Here, the dynamic properties of a number of component candidates are measured using hammer excited vibrational tests. Some of the components are selected to build up wooden assemblies which are evaluated both when they are screwed together and when they are screwed and glued together. The focus is here on achieving representative finite element models of the junctions between the building parts composing the assemblies.

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  • 3.
    Hongisto, V.
    et al.
    Turku University of Applied Sciences, Finland.
    Alakoivu, R.
    Turku University of Applied Sciences, Finland.
    Keränen, J.
    Turku University of Applied Sciences, Finland.
    Hakala, J.
    Turku University of Applied Sciences, Finland.
    Linderholt, A
    Linnaeus University, Sweden.
    Jarnerö, Kirsi
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Laukka, J.
    Turku University of Applied Sciences, Finland.
    Perception of impact sounds through wooden floors was explained by frequencies 100-3150 Hz – Psychoacoustic experiment on annoyance2023In: Proceedings of the 10th Convention of the European Acoustics Association Forum Acusticum 2023, European Acoustics Association , 2023Conference paper (Refereed)
  • 4.
    Hongisto, Valtteri
    et al.
    Turku University of Applied Sciences, Finland.
    Alakoivu, Reijo
    Turku University of Applied Sciences, Finland.
    Keränen, Jukka
    Turku University of Applied Sciences, Finland.
    Hakala, Jarkko
    Turku University of Applied Sciences, Finland.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Jarnerö, Kirsi
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Laukka, Johann
    Turku University of Applied Sciences, Finland.
    PERCEPTION OF IMPACT SOUNDS THROUGH WOODEN FLOORS WAS EXPLAINED BY FREQUENCIES 100-3150 Hz - PSYCHOACOUSTIC EXPERIMENT ON ANNOYANCE2023In: Proceedings of Forum Acusticum 2023, European Acoustics Association, EAA , 2023Conference paper (Refereed)
    Abstract [en]

    The most popular single-number quantities (SNQs) of impact sound insulation in Europe are L’n, w and L’nT, w. They are based on measurements within 100-3150 Hz. Recently, it was proposed that the measurements should be extended down to 25 Hz for wooden floors, and L’nT, w+CI, 25 should replace L’nT, w. The purpose of this study is to analyze which of the two SNQs, Ln, w or LnT, w+CI, 25, predicts the annoyance of natural impact sounds better for wooden floors. We conducted a psychoacoustic experiment, where 52 participants rated the annoyance of 75 impact sounds. As stimuli, five types of natural impact sounds were used. They were recorded for 15 different wooden floors built in an impact sound insulation laboratory, where also their SNQs were measured. Based on correlation analysis, Ln, w explained annoyance of natural impact sounds equally well or better than Ln, w+CI, 25, depending on impact sound type Therefore, based on perception, it seems to be sufficient to conduct measurements within 100-3150 Hz for wooden floors and assess their sound insulation using L’nT, w or L’n, w © 2023 First author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

  • 5.
    Hongisto, Valtteri
    et al.
    Turku University of Applied Sciences, Finland.
    Alakoivu, Reijo
    Turku University of Applied Sciences, Finland.
    Virtanen, J
    Turku University of Applied Sciences, Finland.
    Hakala, J.
    Turku University of Applied Sciences, Finland.
    Saarinen, P.
    Turku University of Applied Sciences, Finland.
    Laukka, J.
    Turku University of Applied Sciences, Finland.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Jarnerö, Kirsi
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Keränen, J.
    Turku University of Applied Sciences, Finland.
    Sound insulation dataset of 30 wooden and 8 concrete floors tested in laboratory conditions2023In: Data in Brief, E-ISSN 2352-3409, Vol. 49, article id 109393Article in journal (Refereed)
    Abstract [en]

    In a Finnish-Swedish consortium project, a large amount of sound insulation tests was conducted for several intermediate floors in laboratory conditions to serve various scientific research questions. The dataset contains 30 wooden and 8 concrete constructions which are commonly used between apartments in multistorey buildings. Impact sound insulation was determined according to ISO 10140-3 standard using both tapping machine and rubber ball as standard sound sources. Airborne sound insulation was determined according to the ISO 10140-2 standard. The data are special since they have a broad frequency range: 20−5000 Hz. Data are reported in 1/3-octave frequency bands and the single-number values of ISO 717-1 and ISO 717-2 are also reported. Detailed construction drawings are available for all reported constructions. The data are highly valuable for research, education, and development purposes since all data were obtained in the same laboratory (Turku University of Applied Sciences, Turku, Finland), and all the constructions were built by the same installation team. © 2023 The Authors

  • 6.
    Hongisto, Valtteri
    et al.
    Turku University of Applied Sciences, Finland.
    Laukka, Johann
    Turku University of Applied Sciences, Finland.
    Alakoivu, Reijo
    Turku University of Applied Sciences, Finland.
    Virtanen, Juho
    Turku University of Applied Sciences, Finland.
    Hakala, Jarkko
    Turku University of Applied Sciences, Finland.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Jarnerö, Kirsi
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Keränen, Jukka
    Turku University of Applied Sciences, Finland.
    Suitability of standardized single-number ratings of impact sound insulation for wooden floors - Psychoacoustic experiment2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684XArticle in journal (Refereed)
    Abstract [en]

    Wooden floors usually have worse impact sound insulation (ISI) at low frequencies than concrete floors having the same rating level. Rating level is usually expressed by single-number quantities (SNQs), such as weighted normalized impact sound pressure level Ln,w. Psychoacoustic research among wooden floors is very limited although a controlled laboratory experiment is the strongest method to point out the most adequate SNQs to be declared for the floors. The purpose of our study was to determine how four standardized SNQs of ISO 717-2, Ln,w, Ln,w + CI, Ln,w + CI,50, and LiA,Fmax,V,T, and a recently proposed SNQ, Ln,w + CI,25, are associated with the annoyance of natural impact sounds transmitted through wooden floors. Fifteen floors were built in the laboratory based either on cross-laminated timber (heavy) or open box wood (light) slabs. Different coverings and suspended ceilings were applied on these slabs. The ISI was tested within 25–3150 Hz using both tapping machine and rubber ball. Thereafter, five natural impact sounds were recorded for each floor: rubber ball drops, steel ball drops, walking, jumping, and chair pushing. Fifty-two people rated the annoyance of these 75 recorded natural impact sounds in psychophysics laboratory. Annoyance was best associated with Ln,w for all the five impact sound types. That is, measurement of ISI within 100–3150 Hz is sufficient from subjective point of view. All four SNQs based on tapping machine explained annoyance better than the SNQ based on rubber ball. Our results can significantly guide the future research, development, and regulations of wooden floors.

  • 7.
    Johansson, M.
    et al.
    Linnaeus University, Sweden.
    Linderholt, A.
    Linnaeus University, Sweden.
    Bolmsvik, Å.
    Linnaeus University, Sweden.
    Jarnerö, Kirsi
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Olsson, Jörgen
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Reynolds, T.
    University of Cambridge, UK.
    Building higher with light-weight timber structures - The effect of wind induced vibrations2015In: INTER-NOISE 2015 - 44th International Congress and Exposition on Noise Control Engineering, The Institute of Noise Control Engineering of the USA, Inc. , 2015Conference paper (Refereed)
    Abstract [en]

    During the last years the interest in multi-storey timber buildings has increased and several medium-to-high-rise buildings with light-weight timber structure have been designed and built. Examples of such are the 8-storey building Limnologen in Växjö, Sweden, the 9-storey Stadthaus in London, UK and being constructed at the moment, the 14-storey building Treet in Bergen, Norway. These are all light-weight and flexible structures which raise questions regarding the wind induced vibrations. For the building in Norway, the calculated vibration properties of the top floor are on the limit of being acceptable according to the ISO 101371 vibration criteria for human comfort. This paper will give a review of building systems for medium-to-high-rise timber buildings. Measured vibration properties for some medium-to-high-rise timber buildings will also be presented. These data have been used for calculating the peak acceleration values for two example buildings for comparison with the ISO standards. An analysis of the acceleration levels for a building with double the height has also been performed showing that designing for wind induced vibrations in higher timber buildings is going to be very important and that more research into this area is needed. © 2015 by ASME.

  • 8.
    Johansson, Marie
    et al.
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Blomqvist, Lars
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Norén, Joakim
    RISE Research Institutes of Sweden.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Prefabricerade ytterväggselement för KL-trästommar2023Report (Other academic)
    Abstract [en]

    Prefabricated external wall elements for CLT systems

    This is a first pre-study to how building with cross-laminated timber (CLT) as a frame system in buildings could be made more efficient using prefabricated exterior wall elements as frame completion for CLT buildings. In carrying out this study, CLT building in Sweden as a rule involves an efficient frame erection of the CLT elements, but with a relatively slow phase to assemble the exterior frame completion. External frame completion of CLT buildings is usually carried out on construction scaffolding, where the layers of insulation and surface layer are built up on site. Prefabrication of the outer layers of the CLT frame that is lifted into place has the potential to save a lot of labor time and thus costs. The report presents requirements and practical aspects that must be taken into account in order for prefabricated exterior wall elements to be feasible in terms of requirements and in practice. The purpose of the report has also been to give tips, inspiration and ideas to consider when producing prefabricated exterior wall elements. In the study, an example solution has been developed with the aim of being wood based to as high degree as possible. The result shows that with relatively simple means it is possible to build a prefabricated wall element that meets established requirements. It is desirable that the outer wall elements are hung in place with the minimum possible finishing work on the facade. When it comes to the division of external wall elements, it is practical to follow a similar division and measurements as for the CLT boards to facilitate handling, assembly and lifting. It should be avoided to have sockets (window panes, door holes and the like) that are broken in its interface between the external wall elements to facilitate uniformity in the dimensioning of the elements. The study shows that it is realistic to create prefabricated exterior wall elements for CLT frames.

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  • 9.
    Johansson, Marie
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, Building Technology.
    Gustafsson, Anders
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, Building Technology.
    Olsson, Jörgen
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, Building Technology.
    Ylmen, Peter
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, Building Technology.
    Nord, Tomas
    Linköping University, Sweden.
    Dorn, Michael
    Linneaus University, Sweden.
    Fruhwald Hansson, Eva
    Lund Universtiy, Sweden.
    Serrano, Erik
    Lund Universtiy, Sweden.
    Broman, Olof
    Luleå University of Technology, Sweden.
    Jansson, Gustav
    Luleå University of Technology, Sweden.
    Sandberg, Dick
    Luleå University of Technology, Sweden.
    Brännström, Mattias
    Renewinn, Sweden.
    Framtidens biobaserade byggande och boende: Slutrapport2019Report (Other academic)
    Abstract [en]

    The aim

    of the project "Biobased building and living for the future" was to create conditions for increased use of bio-based products and services in the construction sector in Sweden and Europe and to increase the competitiveness of the Swedish timber manufacturing industry. The project has shown ways to develop E-commerce, parts of the production where increased digitalization leads to increased capacity and quality, as well as solutions for development of floor systems, external walls and tall timber buildings. The project has shown development opportunities to increase the use of bio-based products that implemented will increase competitiveness.

    The project has been divided into eleven sub-projects to study the various aspects of external factors, market conditions and business models, process development and product development. Within each sub-project, several workshops have been carried out to jointly evaluate results and decide the next step in the sub-project. Through joint workshops, the partners have also been able to meet and share results across the sub-projects and spread knowledge and create networks within the industry. The last part is perceived as very valuable by both the companies and the academy / institute.

    For the joinery value chain, a current situation analysis has been carried out and shown how the development of E-commerce platforms must be combined with process development in order to have a large effect. The results will be utilized in the companies' strategy work ahead. For the timber building value chain, demonstrators have shown development opportunities for both process and product development. The next step for the companies is to evaluate the various solutions linked to their own production conditions.

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  • 10.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Bolmsvik, Åsa
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Jarnerö, Kirsi
    SP Hållbar samhällsbyggnad.
    Olsson, Jörgen
    SP Hållbar samhällsbyggnad.
    Reynolds, Thomas
    University of Cambridge, UK.
    Building higher with light-weight timber structures: the effect of wind induced vibrations2015In: Proceedings of the Internoise 2015 conference, Society of Experimental Mechanics (SEM) , 2015Conference paper (Refereed)
  • 11.
    Linderholt, Andreas
    et al.
    Linnaeus University, Sweden.
    Olsson, Jörgen
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    A simulation based study of low frequency transient sound radiation from floors - A concrete vs. a hybrid floor2017In: 24th International Congress on Sound and Vibration, ICSV 2017, 2017Conference paper (Refereed)
    Abstract [en]

    Timber is a renewable and human friendly construction material and thereby a potential solution to achieve life cycle sustainable buildings. However, it is clear that impact sound and vibrations wit hin the low frequency range still are challenges for wooden joist floors. Another challenge is the, mostly, larger building heights of wooden or hybrid floors compared to the heights of concrete floors. Using timber as the structural joist floor material could imply fewer stories due to maximum allowed building heights, which renders in less income in a building project. Accurate simulations of impact sound may decrease the need for prototypes; thus saving money and time in the timber building industry. Here, a hybrid joist floor consisting of wood, sand and steel is compared to a concrete floor in terms of radiated impact sound into a rectangular cavity. The hybrid floor is designed such that its mass distribution and globa l stiffness are close to the same properties of the concrete floor. Finite element models are used for simulations of the radiated transient sound induced by impact forces having the characteristics of human walking. The simulations indicate that similar surface mass and bending stiffness of a floor intersection give similar impact sound transmission properties around the first bending mode, while it is not necessary so at higher frequencies.

  • 12.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Olsson, Jörgen
    RISE Research Institutes of Sweden AB.
    A simulation based study of low frequency transient sound radiation from floors: a concrete vs. a hybrid floor2017In: Proceedings of the 24th International Congress on Sound and Vibration, Curran Associates, Inc., 2017Conference paper (Other academic)
    Abstract [en]

    Timber is a renewable and human friendly construction material and thereby a potential solution toachieve life cycle sustainable buildings. However, it is clear that impact sound and vibrations withinthe low frequency range still are challenges for wooden joist floors. Another challenge is the,mostly, larger building heights of wooden or hybrid floors compared to the heights of concretefloors. Using timber as the structural joist floor material could imply fewer stories due to maximumallowed building heights, which renders in less income in a building project. Accurate simulationsof impact sound may decrease the need for prototypes; thus saving money and time in the timberbuilding industry. Here, a hybrid joist floor consisting of wood, sand and steel is compared to aconcrete floor in terms of radiated impact sound into a rectangular cavity. The hybrid floor is designedsuch that its mass distribution and global stiffness are close to the same properties of theconcrete floor. Finite element models are used for simulations of the radiated transient sound inducedby impact forces having the characteristics of human walking. The simulations indicate thatsimilar surface mass and bending stiffness of a floor intersection give similar impact sound transmissionproperties around the first bending mode, while it is not necessary so at higher frequencies.Keywords: timber buildings, impact sound, simulation

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  • 13.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Olsson, Jörgen
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Combining testing and calculation for of low frequency sound and vibrations in timber buildings2018In: Forum Wood Building Nordic 2018, 27-28 September 2018, Växjö, Sweden, 2018Conference paper (Other (popular science, discussion, etc.))
  • 14.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Impact and vibration transmission measurements of Masonite Beams AB test house2022Report (Other academic)
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  • 15.
    Olsson, Jörgen
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. SP Technical Research Institute of Sweden.
    Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.

        Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.

        Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.

        The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.

        By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved

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    Licentiate Thesis (Extended Summary)
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    Front Page
  • 16.
    Olsson, Jörgen
    RISE, Sweden; Linneaus Universtiy, Sweden.
    Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.

        Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.

        Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.

        The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.

        By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved.

  • 17.
    Olsson, Jörgen
    Linneaus Univeristy, Sweden; SP Technical Research Institute of Sweden, Sweden.
    Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.     Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.     Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.     The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.     By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved

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  • 18.
    Olsson, Jörgen
    Linneaus Universtiy, Sweden; RISE, Building Technology, Sweden.
    Low Frequency Impact Sound in Timber Buildings: Transmission Measurements and Simulations2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    An increased share of multi-story buildings that have timber structures entails potential in terms of increased sustainability as well as human-friendly manufacturing and habitation. Timber buildings taller than two stories were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden. Thus, being a rather new sector, the multi-story timber building sector lags behind in maturity compared to the multi-story concrete sector. The low-frequency range down to 20 Hz has been shown to be important for the perception of the impact of sound in multi-story apartments with lightweight floors. This frequency range is lower than the one that has traditionally been measured according to standards and regulations. In small rooms, the measurement conditions tend to go from diffuse fields above 100 Hz to modal sound fields dominated by few resonances, below 100 Hz. These conditions lead to new challenges and to new possibilities for measurements and modelling. In the present research, a frequency response functions (FRFs) strategy aimed to simplify simulations and correlations between the simulations and test results was used. Measurements made indicate that, in the low frequencies, the highest sound pressures occur at the floor level opposite the ceiling / floor that is excited. By having an iterative measurement strategy with several microphones and making measurements until a required standard error is obtained, it is possible to gain a desired precision and information about the statistical distribution of both the sound fields and floor insulation performance. It was also found that, depending on the excitation source, the FRF from an excitation point on the floor above to the sound pressure at a microphone position in the room below may differ. This indicates that non-linearities in sound transmissions are present. Thus, the excitation source used in a test should be similar in force levels and characteristics to the real excitation stemming, for instance, from a human footfall, to achieve reliable measurement results. The ISO rubber ball is an excitation source that is close to fulfilling this need. In order to obtain an FRF, the impact force must be known. A rig that enables the impact force from a rubber ball to be measured was developed and manufactured. The results show that the force spectra are the same up to about 55 Hz, regardless of the point impedances of the floors excited in the tests. Similar results have been found by others in tests with human excitations. This means that FRFs up to about 55Hz can be achieved without actually measuring the excitation force. On the calculation side, finite element simulations based on FRFs may offer advantages. FRFs combined with the actual excitation force spectra of interest give the sound transmission. At higher frequencies, it is more important to extract the point mobilities of the floors and relate them to the excitation forces. By using an infinite shaft, sound transmission can be studied without involving reverberation time. The calculation methodology is used in the present research to evaluate different floor designs using FE models.

    Download full text (pdf)
    fulltext
  • 19.
    Olsson, Jörgen
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. RISE Research Institutes of Sweden, Sweden.
    Low Frequency Impact Sound in Timber Buildings: Transmission Measurements and Simulations2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An increased share of multi-story buildings that have timber structures entails potential in terms of increased sustainability as well as human-friendly manufacturing and habitation. Timber buildings taller than two stories were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden. Thus, being a rather new sector, the multi-story timber building sector lags behind in maturity compared to the multi-story concrete sector. The low-frequency range down to 20 Hz has been shown to be important for the perception of the impact of sound in multi-story apartments with lightweight floors. This frequency range is lower than the one that has traditionally been measured according to standards and regulations. In small rooms, the measurement conditions tend to go from diffuse fields above 100 Hz to modal sound fields dominated by few resonances, below 100 Hz. These conditions lead to new challenges and to new possibilities for measurements and modelling.

    In the present research, a frequency response functions (FRFs) strategy aimed to simplify simulations and correlations between the simulations and test results was used. Measurements made indicate that, in the low frequencies, the highest sound pressures occur at the floor level opposite the ceiling / floor that is excited. By having an iterative measurement strategy with several microphones and making measurements until a required standard error is obtained, it is possible to gain a desired precision and information about the statistical distribution of both the sound fields and floor insulation performance. It was also found that, depending on the excitation source, the FRF from an excitation point on the floor above to the sound pressure at a microphone position in the room below may differ. This indicates that non-linearities in sound transmissions are present. Thus, the excitation source used in a test should be similar in force levels and characteristics to the real excitation stemming, for instance, from a human footfall, to achieve reliable measurement results. The ISO rubber ball is an excitation source that is close to fulfilling this need. In order to obtain an FRF, the impact force must be known. A rig that enables the impact force from a rubber ball to be measured was developed and manufactured. The results show that the force spectra are the same up to about 55 Hz, regardless of the point impedances of the floors excited in the tests. Similar results have been found by others in tests with human excitations. This means that FRFs up to about 55Hz can be achieved without actually measuring the excitation force.

    On the calculation side, finite element simulations based on FRFs may offer advantages. FRFs combined with the actual excitation force spectra of interest give the sound transmission. At higher frequencies, it is more important to extract the point mobilities of the floors and relate them to the excitation forces. By using an infinite shaft, sound transmission can be studied without involving reverberation time. The calculation methodology is used in the present research to evaluate different floor designs using FE models.

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    Doctoral Thesis (Comprehensive Summary)
    Download (pdf)
    Spikblad
    Download (jpg)
    Front Page
  • 20.
    Olsson, Jörgen
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Byggande och boende (TRb).
    Model calibration of wooden structure assemblies - Using EMA and FEA2014In: WCTE 2014 - World Conference on Timber Engineering, Proceedings: Renaissance of Timber Construction, 2014Conference paper (Other academic)
  • 21.
    Olsson, Jörgen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Byggande och boende (TRb).
    Andresen, Geir
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Sveriges tekniska forskningsinstitut / Akustik (Eta).
    Akustik i träbyggnader2014Report (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 22.
    Olsson, Jörgen
    et al.
    SP - Technical institute of Sweden.
    Jarnerö, Kirsi
    SP - Technical institute of Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Evaluation of AkuLite measurements of buildings: a comparison between sound pressure stemming from tapping machine and impact ball excitations2015In: Proceedings of the Forum Wood Building Nordic Conference 2015, Växjö, 2015Conference paper (Other academic)
    Abstract [en]

    The impact ball has shown to give excitations in close resemblance with the excitation from a human step. However due to practice and practical measurement reasons, it is interesting to use the tapping machine in low-frequency measurements. Here, the two excitation techniques; the tapping machine and the impact ball, are compared in terms of statistical dispersion. In the AkuLite project light weight apartment buildings were measured using a tapping machine and a (Japanese) impact ball in the low frequency range down to 20 Hz. The results showed that the tapping machine gives more narrow/better confidence interval in the test compared to the test using one excitation point together with the impact ball. The t-test of the consistency of the difference between the impact ball and tapping machine for the same measurement objects shows weak correlation, which implies that the results from the tapping machine are not normally possible to be interchanged with impact ball results and vice versa, without using a correction factor.

    Download full text (pdf)
    fulltext
  • 23.
    Olsson, Jörgen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Jarnerö, Kirsi
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Linderholt, Andreas
    Linneaus University, Sweden.
    Evaluation of AkuLite measurements of buildings: a comparison between sound pressure stemming from tapping machine and impact ball excitations2015In: Proceedings of the Forum Wood Building Nordic Conference Växjö, Växjö, 2015Conference paper (Other academic)
    Abstract [en]

    The impact ball has shown to give excitations in close resemblance with the excitation from a human step. However due to practice and practical measurement reasons, it is interesting to use the tapping machine in low-frequency measurements. Here, the two excitation techniques; the tapping machine and the impact ball, are compared in terms of statistical dispersion. In the AkuLite project light weight apartment buildings were measured using a tapping machine and a (Japanese) impact ball in the low frequency range down to 20 Hz. The results showed that the tapping machine gives more narrow/better confidence interval in the test compared to the test using one excitation point together with the impact ball. The t-test of the consistency of the difference between the impact ball and tapping machine for the same measurement objects shows weak correlation, which implies that the results from the tapping machine are not normally possible to be interchanged with impact ball results and vice versa, without using a correction factor.

  • 24.
    Olsson, Jörgen
    et al.
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    Linderholt, A.
    Linnaeus University, Sweden.
    Measurements of low frequency impact sound transfer functions of light weight timber floors, utilizing the IsO rubber ball2018In: 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling, International Institute of Acoustics and Vibration, IIAV , 2018, p. 476-483Conference paper (Refereed)
    Abstract [en]

    Impact sound below 100 Hz is an important issue for light weight timber buildings. It is also well known that finite element model simulations are more beneficial in the low frequency range than in higher frequencies due to the longer wavelengths allowing the element meshes to be coarser. Utilizing transfer functions to describe impact sound would imply simplifications to correlate data stemming from measurements and low frequency finite element models. If the impact force is known, the simulations become easier since there would not be any need for the modelling of the impact mechanisms, just calculations of the transfer functions which are then combined with the force spectrum to give the resulting sound pressure. The impact ball has shown to be in close resemblance with a human's excitation in the low frequency range which makes it a suitable excitation device. However, when its force spectrum is needed, it may be hard in practice to achieve that during a regular measurement since the ball is not easily equipped with a force gauge. Here, two different methods are investigated. An investigation of the repeatability of the force spectrum of the rubber ball in the low frequency range for floors having different mobilities is made. To enable this, an equipment for field measurements of impact force spectrum and potentially point mobilities using an ISO ball, is designed, manufactured and evaluated. Impact force measurements are made on lightweight timber as well as concrete floors, with different properties for comparisons. Within the lowest frequencies it is potentially possible to use one given force spectrum from the ISO ball together with impact sound measurements for the creation of impact force to sound transfer functions on different floors.

  • 25.
    Olsson, Jörgen
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. RISE, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials.
    Force to sound pressure frequency response measurements using a modified tapping machine on timber floor structures2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 196, article id 109343Article in journal (Refereed)
    Abstract [en]

    In recent years, research has shown that the lower frequency portion of impact sound, down to 20 Hz, is of significant importance to residents' perception in buildings that have lightweight timber floors. At low frequencies, the finite element method is a useful tool for predictive analysis. Impact sound frequency response functions, which are easily calculated using finite element software, are useful as they offer a common ground for studies of correlations between measurements and analyzes. On the measurement side, the tapping machine is well defined and has become the standard excitation device for building acoustics. When using a tapping machine, the excitation force spectrum generated - necessary to achieving experimental frequency force to sound response functions - is unknown. Different equipment may be used for excitation and force measurements and if a structure behaves linearly, the use of any excitation devices should result in the same frequency response functions. Here, an ISO tapping machine hammer is fitted with an accelerometer, enabling estimates of input force spectra. In combination with measurements of the sound in the receiver room, frequency response functions are then achieved using an ISO tapping machine. Various excitation devices have been used on a floor partition in a timber building and on a cross-laminated timber (CLT) lab. floor in order to compare the resulting frequency response functions. Structural nonlinearities are evident, implying that for accurate frequency response measurements in acoustically low frequencies, excitation magnitudes and characteristics that are similar to these which stem from human excitations, should preferably be used.

  • 26.
    Olsson, Jörgen
    et al.
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    Linderholt, Andreas
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    Force to sound pressure frequency response measurements using a modified tapping machine on timber floor structures2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 196, article id 109343Article in journal (Refereed)
    Abstract [en]

    In recent years, research has shown that the lower frequency portion of impact sound, down to 20 Hz, is of significant importance to residents’ perception in buildings that have lightweight timber floors. At low frequencies, the finite element method is a useful tool for predictive analysis. Impact sound frequency response functions, which are easily calculated using finite element software, are useful as they offer a common ground for studies of correlations between measurements and analyzes. On the measurement side, the tapping machine is well defined and has become the standard excitation device for building acoustics. When using a tapping machine, the excitation force spectrum generated – necessary to achieving experimental frequency force to sound response functions – is unknown. Different equipment may be used for excitation and force measurements and if a structure behaves linearly, the use of any excitation devices should result in the same frequency response functions. Here, an ISO tapping machine hammer is fitted with an accelerometer, enabling estimates of input force spectra. In combination with measurements of the sound in the receiver room, frequency response functions are then achieved using an ISO tapping machine. Various excitation devices have been used on a floor partition in a timber building and on a cross-laminated timber (CLT) lab. floor in order to compare the resulting frequency response functions. Structural nonlinearities are evident, implying that for accurate frequency response measurements in acoustically low frequencies, excitation magnitudes and characteristics that are similar to these which stem from human excitations, should preferably be used.

  • 27.
    Olsson, Jörgen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad, Träbyggande och boende.
    Linderholt, Andreas
    Linnæus University, Sweden.
    Impact evaluation of a thin hybrid wood based joist floor2016In: Proceedings of ISMA 2016: International Conference on Noise and Vibration Engineering, 2016, p. 589-602Conference paper (Refereed)
    Abstract [en]

    The purpose of this paper is twofold. The first aim is to develop a numericalanalysis procedure, by combining FRFs from FE-models with analyticalformulas for sound emission and transmission from the ceiling anddownwards within a room with four walls. The aim is to, by applying thisapproach; accomplish a tool which calculates the relative impact soundbetween different joist floors, in the low frequency range. The second aim is tobenchmark a thin hybrid wooden based joist floor with similar thickness,surface weight and global bending stiffness as a concrete hollow core floorstructure. What will be the difference in sound transmission? The question isrelevant since it may be necessary to make thinner wood based joist floors inhigh rise buildings, if wood should stay competitive against concrete. Theresults show that the direct transmissions of impact sound are very similararound the first bending mode. As the frequency increases, the modes in thestructures differ significantly. Below 100 Hz, the concrete floor has 4 modes,while the hybrid joist floor has 9 modes. As the frequency increases the soundradiation characteristics differs. The results show that it is possible to havesimilar sound transmission properties around the first bending modes for ahybrid based joist floor and a hollow core concrete floor structure with similar thicknesses. At the first modes of the structure, the information about thesurface weight and global bending stiffness are useful for prediction of soundtransmission properties but for higher modes, they are not sufficient.

  • 28.
    Olsson, Jörgen
    et al.
    SP Technical Research Institute of Sweden, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Low Frequency Force to Sound Pressure Transfer Function Measurements Using a Modified Tapping Machine on a Light Weight Wooden Joinst Floor2016In: Proceedings of WCTE, World Conference on timber Engineering, August 22-25, 2016, Vienna, Austria, Vienna: Vienna University of Technology , 2016Conference paper (Other academic)
    Abstract [en]

    In recent years research has shown that low frequency impact sound is of significant importance for inhabitants´ perception of impact sound in buildings with light weight wooden joist floors. The tapping machine is well defined as an excitation device and is a standard tool for building acoustics. However, the excitation force spectrum generated for each individual floor is unknown when using a tapping machine. In order to increase the possibilities to compare simulations to impact sound measurements, there is a need for improvement of impact sound measurement methods. By measuring the input force spectrum by a modified tapping machine and the sound in the receiver room, transfer functions can be achieved.In the light weight wooden building used for the evaluation test of the proposed method, structural nonlinearities are evident in the frequency response functions stemming from different excitation levels. This implies that for accurate FRF-measurements in low frequencies, excitation magnitudes that are similar to these stemming from human excitations should preferably be used.

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    LOW FREQUENCY FORCE TO SOUND PRESSURE TRANSFER FUNCTION MEASUREMENTS USING A MODIFIED TAPPING MACHINE ON A LIGHT WEIGHT WOODEN JOIST FLOOR
  • 29.
    Olsson, Jörgen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Linderholt, Andreas
    Linnæus University, Sweden.
    Low Frequency Force to Sound Pressure Transfer Function Measurements Using a Modified Tapping Machine on a Light Weight Wooden Joist Floor2016In: WCTE 2016: World Conference on Timber Engineering, 2016, p. 2888-2895Conference paper (Refereed)
    Abstract [en]

    In recent years research has shown that low frequency impact sound is of significant importance for inhabitants´ perception of impact sound in buildings with light weight wooden joist floors. The tapping machine is well defined as an excitation device and is a standard tool for building acoustics. However, the excitation force spectrum generated for each individual floor is unknown when using a tapping machine. In order to increase the possibilities to compare simulations to impact sound measurements, there is a need for improvement of impact sound measurement methods. By measuring the input force spectrum by a modified tapping machine and the sound in the receiver room, transfer functions can be achieved.In the light weight wooden building used for the evaluation test of the proposed method, structural nonlinearities are evident in the frequency response functions stemming from different excitation levels. This implies that for accurate FRF-measurements in low frequencies, excitation magnitudes that are similar to these stemming from human excitations should preferably be used.

  • 30.
    Olsson, Jörgen
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. RISE, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials.
    Low-frequency impact sound of timber floors: A finite element–based study of conceptual designs2021In: Building Acoustics, ISSN 1351-010X, Vol. 28, no 1, p. 17-34Article in journal (Refereed)
    Abstract [en]

    Traditionally, product development concerning acoustics in the building industry is measurement oriented.For lightweight floors, frequencies that are lower than the frequency range for heavy concrete floors are anissue. The frequency range of from 50 Hz down to 20 Hz influences the human perception of impact sound inmulti-story apartment buildings with lightweight floor constructions, such as timber floors, for example. It iswell known that a lower frequency range of interest makes finite element simulations more feasible. Strategiesfor reducing impact sound tend to be less straightforward for timber floors because they have a largervariation of designs when compared to concrete floors. This implies that reliable finite element simulations ofimpact sound can save time and money for the building industry. This study researches the impact soundtransmission of lightweight timber floors. Frequency response functions, from forces on excitation points tosound pressure in the receiving cavity below, are calculated. By using fluid elements connected to reflectionfreeboundary elements under the floors in the models, the transmission and insulation can be studied withoutinvolving reverberation. A floor model with a hard screed surface will have a larger impact force than a softerfloor, although this issue seems less pronounced at the lowest frequencies. To characterize floor surfaces, thepoint mobilities of the impact points are also calculated and presented. The vibration and sound transmissionlevels are dependent on the selection of the excitation points.

  • 31.
    Olsson, Jörgen
    et al.
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate. Linnaeus University, Sweden.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Low-frequency impact sound of timber floors: A finite element–based study of conceptual designs2021In: Building Acoustics, ISSN 1351-010X, Vol. 28, no 1, p. 17-34Article in journal (Refereed)
    Abstract [en]

    Traditionally, product development concerning acoustics in the building industry is measurement oriented. For lightweight floors, frequencies that are lower than the frequency range for heavy concrete floors are an issue. The frequency range of from 50 Hz down to 20 Hz influences the human perception of impact sound in multi-story apartment buildings with lightweight floor constructions, such as timber floors, for example. It is well known that a lower frequency range of interest makes finite element simulations more feasible. Strategies for reducing impact sound tend to be less straightforward for timber floors because they have a larger variation of designs when compared to concrete floors. This implies that reliable finite element simulations of impact sound can save time and money for the building industry. This study researches the impact sound transmission of lightweight timber floors. Frequency response functions, from forces on excitation points to sound pressure in the receiving cavity below, are calculated. By using fluid elements connected to reflection-free boundary elements under the floors in the models, the transmission and insulation can be studied without involving reverberation. A floor model with a hard screed surface will have a larger impact force than a softer floor, although this issue seems less pronounced at the lowest frequencies. To characterize floor surfaces, the point mobilities of the impact points are also calculated and presented. The vibration and sound transmission levels are dependent on the selection of the excitation points. © The Author(s) 2020.

  • 32.
    Olsson, Jörgen
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. RISE, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Low-frequency impact sound pressure fields in small rooms within lightweight timber buildings - suggestions for simplified measurement procedures2018In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 66, no 4, p. 324-339Article in journal (Refereed)
    Abstract [en]

    Low-frequency impact sound insulation, down to 20 Hz, has a significant effect on humans' dissatisfaction due to noise in timber buildings. Today, the low-frequency procedure of the ISO 16283-2:2015 impact sound measurement standard covers the frequency range down to 50 Hz for the use of an ISO tapping machine, but does not yet cover the use of an ISO rubber ball. Here, microphone grid measurements were made in two small rooms that were excited by an ISO rubber ball from the rooms above. In each grid, 936 microphone positions were used to capture data representing the full spatial fields of impact sound pressures from 10 to 500 Hz for one excitation location for each room. The data show that the positions at the radiating ceiling surfaces have low maximum sound pressure levels compared to the pressure levels at the floors, especially in the floor corners. First, a measurement procedure to predict the maximum exposure of low-frequency sound in a room is proposed It is suggested that the maximum values for each frequency band in the corners opposite to the partition being excited (i.e., the floor corners) be used. Second, a procedure to predict the room average sound pressure level and the prediction's normal distribution is suggested. Iterative measurements with random microphone locations and random excitation locations are used. The advantage of this method is that the required precision and information about the sensitivity due to different excitation points are obtained. (c) 2018 Institute of Noise Control Engineering.

  • 33.
    Olsson, Jörgen
    et al.
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    Linderholt, Andreas
    Linneaus University, Sweden.
    Low-frequency impact sound pressure fields in small rooms within lightweight timber buildings — Suggestions for simplified measurement procedures2018In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 66, no 4, p. 324-339Article in journal (Refereed)
    Abstract [en]

    Low-frequency impact sound insulation, down to 20 Hz, has a significant effect on humans' dissatisfaction due to noise in timber buildings. Today, the low-frequency procedure of the ISO 16283-2:2015 impact sound measurement standard covers the frequency range down to 50 Hz for the use of an ISO tapping machine, but does not yet cover the use of an ISO rubber ball. Here, microphone grid measurements were made in two small rooms that were excited by an ISO rubber ball from the rooms above. In each grid, 936 microphone positions were used to capture data representing the full spatial fields of impact sound pressures from 10 to 500 Hz for one excitation location for each room. The data show that the positions at the radiating ceiling surfaces have low maximum sound pressure levels compared to the pressure levels at the floors, especially in the floor corners. First, a measurement procedure to predict the maximum exposure of low-frequency sound in a room is proposed It is suggested that the maximum values for each frequency band in the corners opposite to the partition being excited (i.e., the floor corners) be used. Second, a procedure to predict the room average sound pressure level and the prediction's normal distribution is suggested. Iterative measurements with random microphone locations and random excitation locations are used. The advantage of this method is that the required precision and information about the sensitivity due to different excitation points are obtained.

  • 34.
    Olsson, Jörgen
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. RISE, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials.
    Measurements of low frequency impact sound frequency response functions and vibrational properties of light weight timber floors utilizing the ISO rubber ball2020In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 166, p. 1-10, article id 107313Article in journal (Refereed)
    Abstract [en]

    Impact sound performance below 100 Hz forms part of a design criterio that is particularly important for multi-story timber buildings. An ISO tapping machine, which is predominantly used for impact sound measurement, has properties that may result in less measurement accuracy in the low frequency range, down to 20 Hz, than in its traditional measurement range above 100 Hz. The characteristics of the pistons’ impact are dissimilar to the impact of a human foot in this lower range. This may cause low signal-to-noise ratios in field measurements and the test data may also be less representative due to the test objects’ possible structural nonlinearities affecting impact sound transmission. The ISO rubber ball has shown to bear a close resemblance to a human’s excitation in the low frequency range, which makes it a suitable excitation device from this perspective. To support correlations between simulations and measurements, measuring impact forces in order to extract frequency response functions would be beneficial. To enable measurements of impact forces that stem from the ISO rubber ball, equipment for field measurements of forces and potentially point mobilities has been manufactured and evaluated. Furthermore, an investigation has been conducted into the repeatability of the rubber ball’s low frequency force spectrum for floors with different mobilities. Impact force measurements have been made on lightweight timber floors as well as on concrete floors. Within the frequency range up to around 55 Hz, it appears to be possible to use a prescribed force spectrum for the ISO ball, together with impact sound measurements, to create accurate impact force to sound frequency response functions for different floors. Also, instrumenting the impact point with an accelerometer enables estimates to be made of direct point mobilities.

  • 35.
    Olsson, Jörgen
    et al.
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate. Linnaeus University, Sweden.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Measurements of low frequency impact sound frequency response functions and vibrational properties of light weight timber floors utilizing the ISO rubber ball2020In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 166, article id 109343Article in journal (Refereed)
    Abstract [en]

    Impact sound performance below 100 Hz forms part of a design criterio that is particularly important for multi-story timber buildings. An ISO tapping machine, which is predominantly used for impact sound measurement, has properties that may result in less measurement accuracy in the low frequency range, down to 20 Hz, than in its traditional measurement range above 100 Hz. The characteristics of the pistons’ impact are dissimilar to the impact of a human foot in this lower range. This may cause low signal-to-noise ratios in field measurements and the test data may also be less representative due to the test objects’ possible structural nonlinearities affecting impact sound transmission. The ISO rubber ball has shown to bear a close resemblance to a human’s excitation in the low frequency range, which makes it a suitable excitation device from this perspective. To support correlations between simulations and measurements, measuring impact forces in order to extract frequency response functions would be beneficial. To enable measurements of impact forces that stem from the ISO rubber ball, equipment for field measurements of forces and potentially point mobilities has been manufactured and evaluated. Furthermore, an investigation has been conducted into the repeatability of the rubber ball’s low frequency force spectrum for floors with different mobilities. Impact force measurements have been made on lightweight timber floors as well as on concrete floors. Within the frequency range up to around 55 Hz, it appears to be possible to use a prescribed force spectrum for the ISO ball, together with impact sound measurements, to create accurate impact force to sound frequency response functions for different floors. Also, instrumenting the impact point with an accelerometer enables estimates to be made of direct point mobilities.

  • 36.
    Olsson, Jörgen
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. RISE, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Measurements of low frequency impact sound transfer functions of light weight timber floors, utilizing the ISO rubber ball2018In: Proceedings of the 25th International Congress on Sound and Vibration, The International Institute of Acoustics and Vibration , 2018, p. 1-8Conference paper (Other academic)
    Abstract [en]

    Impact sound below 100 Hz is an important issue for light weight timber buildings. It is also well known that finite element model simulations are more beneficial in the low frequency range than in higher frequencies due to the longer wavelengths allowing the element meshes to be coarser. Utilizing transfer functions to describe impact sound would imply simplifications to correlate data stemming from measurements and low frequency finite element models. If the impact force is known, the simulations become easier since there would not be any need for the modelling of the impact mechanisms, just calculations of the transfer functions which are then combined with the force spectrum to give the resulting sound pressure. The impact ball has shown to be in close resemblance with a human's excitation in the low frequency range which makes it a suitable excitation device. However, when its force spectrum is needed, it may be hard in practice to achieve that during a regular measurement since the ball is not easily equipped with a force gauge. Here, two different methods are investigated. An investigation of the repeatability of the force spectrum of the rubber ball in the low frequency range for floors having different mobilities is made. To enable this, an equipment for field measurements of impact force spectrum and potentially point mobilities using an ISO ball, is designed, manufactured and evaluated. Impact force measurements are made on lightweight timber as well as concrete floors, with different properties for comparisons. Within the lowest frequencies it is potentially possible to use one given force spectrum from the ISO ball together with impact sound measurements for the creation of impact force to sound transfer functions on different floors.

    Download full text (pdf)
    fulltext
  • 37.
    Olsson, Jörgen
    et al.
    SP Technical Research Institute of Sweden, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Jarnerö, Kirsi
    SP Technical Research Institute of Sweden, Sweden.
    Low frequency sound pressure fields in small rooms in wooden buildings with dense and sparse joist floor spacings2015In: Proceedings of the Internoise 2015 conference: 44th International Congress and Exposition on Noise Control Engineering / [ed] Maling G.,Burroughs C., The Institute of Noise Control Engineering of the USA , 2015Conference paper (Refereed)
    Abstract [en]

    Using wood as the main construction material is a potential solution to achieve sustainable buildings. Previous research has shown that frequencies below 50 Hz are of significant importance for the perception of impact sound by residents living in multi-story buildings having light weight wooden frameworks. The standards used for impact sound measurements today are developed for diffuse fields above 50 Hz. For instance due to requirements concerning wall reflections, these methods are not applicable for low frequencies within small rooms. To improve measurement methods, it is important to know the nature of the full sound distribution in small rooms having wooden joist floors. Here, impact sound measurements with microphone arrays are made in two small office rooms having the same dimensions. The rooms represent two extremes in design of joist floors; one with closely spaced wood joists and the other with widely spaced joists. An impact ball is used for excitation the room being measured from the room above. The results show that there are significant variations in the sound pressure, especially in the vertical direction. Here, measurement techniques of impact sound in the low frequency range in small rooms in wooden buildings are evaluated and potential improvements are proposed.

  • 38.
    Olsson, Jörgen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Bygg och Mekanik.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Jarnerö, Kirsi
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Bygg och Mekanik.
    Low frequency sound pressure fields in small rooms in wooden buildings with dense and sparse joist floor spacings2015In: Proceedings of the INTER-NOISE 2015 - 44th International Congress on Noise Control Engineering: Implementing Noise Control Technology, 2015, Vol. 1, p. 652-663Conference paper (Refereed)
    Abstract [en]

    Using wood as the main construction material is a potential solution to achieve sustainable buildings. Previous research has shown that frequencies below 50 Hz are of significant importance for the perception of impact sound by residents living in multi-story buildings having light weight wooden frameworks. The standards used for impact sound measurements today are developed for diffuse fields above 50 Hz. For instance due to requirements concerning wall reflections, these methods are not applicable for low frequencies within small rooms. To improve measurement methods, it is important to know the nature of the full sound distribution in small rooms having wooden joist floors. Here, impact sound measurements with microphone arrays are made in two small office rooms having the same dimensions. The rooms represent two extremes in design of joist floors; one with closely spaced wood joists and the other with widely spaced joists. An impact ball is used for excitation the room being measured from the room above. The results show that there are significant variations in the sound pressure, especially in the vertical direction. Here, measurement techniques of impact sound in the low frequency range in small rooms in wooden buildings are evaluated and potential improvements are proposed.

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  • 39.
    Olsson, Jörgen
    et al.
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Linderholt, Andreas
    Linnaeus University, Sweden.
    Jarnerö, Kirsi
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Hongisto, Valtteri
    Turku University of Applied Science, Finland.
    Incremental use of FFT as a solution for low BT-product reverberation time measurements2023In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 203, article id 109191Article in journal (Refereed)
    Abstract [en]

    The limitations in performance of band-pass filters to accurately process rapid decaying signals in lower frequency bands is an obstacle for some measurements within building acoustics. For instance, it would be beneficial to be able to accurately measure reverberation times down to the 20 Hz one-third octave band for impact sound in timber buildings. Here, it is tested whether calculations with FFT with small incremental steps may be a way to achieve discrete frequency time signals with faster performance than traditional band-pass filters. The tests show that incremental FFT gives accurate estimations of the reverberation time corresponding down to 0.1 s at 20 Hz with a spectral resolution of 2 Hz. Using the one-third octave limits it is possible to form approximate one-third octave band results. It is seen that accurate estimations of reverberation time are achievable for BT⩾0.5 (T=0.1 seconds for the 20 Hz one-third octave band) and possibly even lower, if the dynamic range in the interrupted noise signal is sufficient. The higher one-third octave results show to work as well. A disadvantage with the method is that during short reverberation times (0.1 s) there is a severe spectral leakage to the side bands. Also, the method requires higher dynamic range decay signals compared to band-pass filtered signals. If a one-third octave resolution is requested, a dynamic range of 50 dB or greater is preferable. With a coarse resolution of e.g., 10 Hz and having no averaging into one-third octave bands, it is possible to measure short reverberation times (0.1 s) with signals having close to the same dynamic range used in classical band-pass filtered reverberation time measurements. © 2022 The Author(s)

  • 40.
    Olsson, Jörgen
    et al.
    SP Technical Research Institute.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Nilsson, Börje
    Linnaeus University, Faculty of Technology, Department of Mathematics.
    Impact evaluation of a thin hybrid wood based joist floor2016In: Proceedings of ISMA 2016, presented at the International Conference on Noise andVibration Engineering (ISMA) / [ed] Sas, P; Moens, D; VanDeWalle, A, Leuven, Belgium: Katholieke University Leuven , 2016, p. 589-602Conference paper (Refereed)
    Abstract [en]

    The purpose of this paper is twofold. The first aim is to develop a numericalanalysis procedure, by combining FRFs from FE-models with analyticalformulas for sound emission and transmission from the ceiling anddownwards within a room with four walls. The aim is to, by applying thisapproach; accomplish a tool which calculates the relative impact soundbetween different joist floors, in the low frequency range. The second aim is tobenchmark a thin hybrid wooden based joist floor with similar thickness,surface weight and global bending stiffness as a concrete hollow core floorstructure. What will be the difference in sound transmission? The question isrelevant since it may be necessary to make thinner wood based joist floors inhigh rise buildings, if wood should stay competitive against concrete. Theresults show that the direct transmissions of impact sound are very similararound the first bending mode. As the frequency increases, the modes in thestructures differ significantly. Below 100 Hz, the concrete floor has 4 modes,while the hybrid joist floor has 9 modes. As the frequency increases the soundradiation characteristics differs. The results show that it is possible to havesimilar sound transmission properties around the first bending modes for ahybrid based joist floor and a hollow core concrete floor structure with similar thicknesses. At the first modes of the structure, the information about thesurface weight and global bending stiffness are useful for prediction of soundtransmission properties but for higher modes, they are not sufficient.

  • 41.
    Olsson, Jörgen
    et al.
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Norén, Joakim
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Parida, Gabriela
    Luleå University of Technology , Sweden.
    Esquivel, Adam
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate. Sweco, Sweden.
    Söderström, Hans
    Expert installationsteknik - VVS, Sweden.
    Vägledning för påbyggnader i trä – Byggsystem: Timber on Top2022Report (Other academic)
    Abstract [en]

    Increased construction with timber is a potential way to improve environmental impact of the construction sector. If it is done right, timber is a renewable, sustainable and requires low amount of energy in the construction phase and during its service life. Vertical extensions of buildings are a potential way to increase a buildings relevant service life and to adapt the building to the increased needs of a city. It is also a way to contribute to densify cities with less resources compared to demolish the building and to construct a new one. Vertical extensions made with timber is light, compared to for instance concrete. This decrease the need for, or amount of, reinforcements needed in the existing building that is to be extended. There is a large unused potential in vertical extensions. Only a small amount of buildings is extended during its service life. The main purpose with this guide is to support developers and people that are involved in early stages of discussions and planning vertical extension of a building. It should also be useful as a support for technical people involved vertical extensions. Interviews with consultants and construction companies have shown that projects with vertical extensions is best run slightly different compared to normal projects were one start from “an empty plot”. In a project where you start from an empty plot, the developer and architects may normally be able to work rather free and independent from designers and heating, ventilation, and air conditioning engineers, in the early part of the project. For vertical extension projects the situation is different. The existing building possess special qualities and boundary conditions. For a successful project it is important to understand these technical possibilities and limitations. This is conveniently done by educate the developer in some of these parts, in order to understand what potential different buildings may have with vertical extensions and how some selections of concepts may complicate the extension. For the architect it is also important to work closely with the structural designer and the heating, ventilation, and air conditioning engineer from the beginning of the project, as a team. Experience have shown that not doing so may give concepts that is difficult to accomplish and needs for costly revisions. The first part of the process to decide if a building is suitable for vertical extensions is to investigate the condition of the existing building. Especially the load carrying capacity of the ground and the building, possible need for reinforcement and how reinforcements may be done. This is important understandings in the earliest parts of a project that usually need to be investigated or clarified. Building vertical extensions with timber may be done with a variety of building systems. Each have its benefits and limitations. Cross Laminated Timber (CLT) and post and beam building systems may be tailored in rather detailed dimensions adapted to the existing building. However, they require usually more installation work on building site compared to pre-fabricated modules. Post and beam are usually better for larger buildings. Pre-fabricated modules allows more of efficient pre-production in a factory but may require more framing structure and a higher connection part between the existing building and the extension. This due to modular systems tend to have more standard sizes which is not adapted to the existing building. In total, it is usually possible to achieve effective and aesthetical vertical extensions with timber building systems.

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  • 42.
    Olsson, Jörgen
    et al.
    Byggande och boende (TRb).
    Sjökvist, Lars-Göran
    SP- Sveriges Tekniska Forskningsinstitut, Trätek.
    Jarnerö, Kirsi
    SP- Sveriges Tekniska Forskningsinstitut, Trätek.
    Low frequency measurements of impact sound performance in light weight timber frame office buildings2012In: Proceedings of EURONOISE 2012, European Acoustics Association, European Acoustics Association (EAA), 2012Conference paper (Refereed)
  • 43.
    Olsson, Jörgen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Byggande och boende (TRb).
    Sjökvist, Lars-Göran
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    Jarnerö, Kirsi
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    Low frequency measurements of impact sound performance in light weight timber frame office buildings2012In: Proceedings of EURONOISE 2012, European Acoustics Association , 2012, , p. 6p. 191-196Conference paper (Refereed)
    Abstract [en]

    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.

  • 44.
    Sandin, Ylva
    et al.
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Sandin, Gustav
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Cristescu, Carmen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Olsson, Jörgen
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Kunskapsläge kring byggnader med stomme av trä: teknik, hållbarhet och cirkulär materialanvändning2020Report (Other academic)
    Abstract [en]

    More use of biobased materials has been proposed as important for reducing the high resource use and severe environmental impact of buildings. For increased and sound use of biobased building materials, decision makers need information on their technical and sustainability performance – but there is a lack of an updated synthesis of such information in the scientific literature. Therefore, this project has gathered scientific knowledge on the technical and sustainability viability of biobased building materials, with a focus on load-bearing structures.

    Specific objectives were to:

    a) Clarify technical challenges that bio-based building frames have been associated with, and how these have been handled.

    b) Clarify the sustainability impact of bio-based building frames, in a life-cycle perspective, compared to non-bio-based building frames.

    c) Explore the opportunities for bio-based building frames to be part of a circular economy, in terms of their reusability and recyclability.

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  • 45.
    Scheepers, Gerhard
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, Biobased Materials.
    Olsson, Jörgen
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, Building Technology.
    Lycken, Anders
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, Biobased Materials.
    Grahn, Thomas
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, Papermaking and Packaging.
    Lundqvist, Sven-Olof
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, Biorefinery and Energy.
    Hagman, Olle
    Luleå University of Technology, Sweden.
    Hållfasthetsbestämning av virke med en NIR-kamera2017Report (Other academic)
    Abstract [sv]

    SP, Innventia och Luleås Tekniska Universitet har genomfört en förstudie där man undersökte om nära-infrarött (NIR) data kan bidra till säkrare hållfasthetsbestämning av virke. För att göra det behövdes förutom NIR-data, dels data som konventionellt används i sågverk för att göra hållfasthets-uppskattningar, dels referensdata från mekanisk provning.

    Följande data samlades in från 100 granplankor med dimensionen 3600*150*45 mm3:

    1. mått, vikt, och därmed densitet,

    2. egenfrekvenser via dynamisk excitering,

    3. högupplösta NIR-bilder på 2 flatsidor av varje planka,

    4. RGB och fibervinkeldata från flat- och kantsidorna,

    5. röntgentomografibilder,

    6. förstörande böjtestdata, med bestämning av lokal och global E-modul, och

    7. kvalitativ inventering av brottyp och kvistposition.

     

    Databasen är i sig en värdefull resurs och en god grund för fortsatt forskning och utveckling mot kun-skap och tillämpningar baserat på information som hittills inte utvärderats och nyttjats.

    Virkesegenskaper som påverkar hållfasthet, såsom tjurved, kunde identifieras och visualiseras. Andra egenskaper som är viktiga hållfasthetsindikatorer, såsom egenfrekvens och densitet, kunde predikteras med multivariata modeller baserade på NIR-spektraldata. Inledande modellförsök visar att det går att prediktera global E-modul med multivariata modeller baserade på NIR-spektraldata med ungefärlig samma precision som industriell hållfasthetsbedömning med dynamisk excitering. De NIR-data som användes i modelleringen var dock bara medelvärden över hela plankan. Därför finns det god potential för bättre prediktion med mer riktade variabler, som speglar de spatiala variationerna i varje planka, t.ex. runt kvistar, vilket blir ämnet för ett eventuellt fortsättningsprojekt.

    Projektet finansierades av Norrskogs Forskningsstiftelse, Stiftelsen Åforsk, Träcentrum Norr, och Södra Skogsägarnas Stiftelse för Forskning, Utveckling och Utbildning. Individer som medverkade i projektet inkluderar Gerhard Scheepers, Jörgen Olsson, Anders Lycken, Sven-Olof Lundqvist och Thomas Grahn (RISE Bioekonomi); och Olle Hagman (LTU). RemaSawco och JGA i Linneryd hjälpte också med insamlingen av fibervinkeldata.

     

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