The wooden multi-storey building industry is facing persistent sound transmission problems at low frequencies. Inserting elastomers within wall-floor junctions is common usage nevertheless no accurate studies have elucidated the real behavior of those nonlinear combined materials yet. Deeper knowledge is needed to create a relevant FE model which will help industry to use those materials efficiently.The nonlinear dynamic behavior of the elastomers inserted in wooden junctions is analyzed while the static load acting on them is varying. The specific situation where those elastomers were tested is a scaled room made of two walls and one floor.An experimental study was conducted on this prototype wooden construction and a numerical analysis was performed on the Finite Element model of it. The frequency response functions of several positions were measured on the physical setup.The study showed that loaded structures (up to 2 times the load of the floor) had a lower damping ratio. Having the structure standing on really stiff or elastic material does not differ when comparing experimental and analytical modal parameters.Those results depict the behavior of elastomers for different load cases and are definitely a step forward for the conception of a reliable FE model.

The standard, EN12354-1 describes a simplified statistical energy analysis (SEA) model to predict the apparent sound reduction index between two rooms inclusive of the contributions of the flanking paths. There is interest worldwide in applying the EN12354 model to lightweight building elements. However, lightweight elements typically do not meet the requirements of an SEA subsystem and therefore applying the EN12354 model to these elements may result in inaccurate predictions. The purpose of this investigation was to systematically evaluate the application of the EN12354 model to lightweight building constructions. The evaluation included the determination of the probability density functions and the propagated uncertainty of the calculations. Knowledge of the probability density functions resulted in alternative calculations of the structure-borne sound transmitted through the constructions. The uncertainty analysis revealed that the uncertainty of the predictions is directly affected by the variance of the vibratory field measured on the elements. The vibratory fields of lightweight elements typically show large variances and therefore the propagated uncertainty of the EN12354 predictions for these elements can be significant. The investigation included measurements both in the laboratory and in the field. The results of the laboratory measurements were compared to both predictions using the EN12354 methods and ESEA models which included higher order flanking paths and non-resonant transmission paths. The field measurements included in this investigation were unique because the flanking intensity sound reduction indices of the elements in the source room were measured. The measurements allowed for the EN12354 predictions for each flanking element to be assessed instead of just the apparent sound reduction index between the rooms. The study resulted in proposed correction factors for when reciprocity does not hold and proposed changes to ISO10848 to improve the accuracy of the predictions when the EN12354 method was applied to lightweight building elements. However, neither the proposed correction factors nor the proposed changed to ISO10848-1 could correct for the potentially large differences between the predicted and the measured results. Based on the findings of this study, the use of the EN12354 model for the calculation of the apparent sound reduction index of lightweight elements is not endorsed. Lightweight constructions may not be categorized as ideal SEA subsystems due to the lack of diffuseness of the vibratory field. Furthermore, in order for EN12354 to be applied to lightweight constructions, a reliable method of calculating the resonant component of the sound reduction index of double-leaf elements is required. Therefore, statistical methods including the EN12354 method may be unsuitable for use for the prediction of flanking noise for lightweight building constructions.

This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission. Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain. In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs. Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models. The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed. / Denna doktorsavhandling behandlar flanktransmission i flervåningshus med trästomme, inom det lågfrekventa området, främst 20-120 Hz. Det övergripande målet är att undersöka hur finita elementmetoden kan bidra i konstruktionsfasen för att utvärdera olika knutpunkters inverkan på flanktransmissionen. Två fältmätningar av accelerationer i trähus har utvärderats. I dessa har två olika lastkällor använts, i den första en stegljudsapparat och i den andra en elektrodynamisk vibrator (shaker). Det visades att shakern kan ge mer detaljerad information, men eftersom vibrationerna även sprider sig till omgivande byggnadsdelar vid fältmätningarna var det svårt att estimera tillförlitliga dämpningsdata även då shaker användes. Fältmätningarna följdes av två mätningar i laborationsmiljö. Dessa två experiment utvärderades med experimentell modalanalys, vilket ger egenmoder och dämpning hos strukturerna. Dämpningen för dessa trähuskonstruktioner varierar kraftigt med frekvens. Extra stora variationer registreras då en elastomer användes i knutpunkten mellan golv och vägg. Den totala dämpningen är generellt högre när elastomerer används i knutpunkten mellan golv och vägg i jämförelse med då knutpunkten är skruvad. Genom att analysera egenmoder och deras korrelationer (MAC), för samma trästruktur men med olika typer av knutpunkter, drogs slutsatsen att knutpunkten drastiskt förändrar strukturens dynamiska beteende. Flera finita elementmodeller av både fält- och laboratorieuppställningar har gjorts. I dessa har knutpunkterna mellan byggnadsdelar modellerats helt styvt eller med hjälp av fjädrar och dämpare. Visuella observationer av egenmoder och korrelationen dem emellan visar att det finns mer rotationsstyvhet i försöken än i finita elementmodellerna. Resultaten i denna doktorsavhandling har gett förståelse för hur knutpunkter i träkonstruktioner beter sig och kan simuleras med finit elementmodellering. Vidare kan resultaten bidra till utvecklingen av FE-modeller som kan användas för att kunna se de akustiska effekterna redan under konstruktionsstadiet. Dock behövs ytterligare forskning inom området.