| 1. |
- Bader Eddin, Mohamad, et al.
(author)
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A sound insulation prediction model for floor structures in wooden buildings using neural networks approach
- 2021
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In: Proceedings of INTER-NOISE 2021 - 2021 International Congress and Exposition of Noise Control Engineering. - 0736-2935. - 9781732598652
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Conference paper (other academic/artistic)abstract
- Reliable prediction tools are yet to be developed for estimating the accurate acoustic performance of lightweight structures, which are vital especially in the design process. This paper presents a sound insulation prediction model based on artificial Neural Networks (NN) to estimate acoustic performance for airborne and impact sound insulation of floor structures. At an initial stage, the prediction model was developed and tested for a small amount of data, specifically 67 laboratory measurement curves in one third octave bands. The results indicate that the model can predict the weighted airborne reduction index Rw for various floors with a maximum error of 1 dB. The accuracy decreases with errors up to 9 dB for the weighted index for impact sound Ln,w, in cases of complex floor configurations due to large error deviations in high frequency bands between the real and estimated values. The model also shows a very good accuracy in predicting the airborne and impact sound insulation curves in the low frequencies, which are of higher interest usually in building acoustics.
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| 2. |
- Bader Eddin, Mohamad, et al.
(author)
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Prediction of Sound Insulation Using Artificial Neural Networks—Part II : Lightweight Wooden Façade Structures
- 2022
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In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:14
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Journal article (peer-reviewed)abstract
- A prediction model based on artificial neural networks is adapted to forecast the acoustic performance of airborne sound insulation of various lightweight wooden façade walls. A total of 100 insulation curves were used to develop the prediction model. The data are laboratory measurements of façade walls in one-third-octave bands (50 Hz–5 kHz). For each façade wall, geometric and physical information (material type, dimensions, thicknesses, densities, and more) are used as input parameters. The model shows a satisfactory predictive capability for airborne sound reduction. A higher accuracy is obtained at middle frequencies (250 Hz–1 kHz), while lower and higher frequency ranges often show higher deviations. The weighted airborne sound reduction index ((Formula presented.)) of façades can be estimated with a maximum difference of 3 dB. Sometimes, the model shows high variations within fundamental and critical frequencies that influence the predictive precision. A sensitivity analysis is implemented to investigate the significance of parameters in insulation estimations. The material density (i.e., cross-laminated timber panel, gypsum board), thickness of the insulation materials, thickness and spacing between interior studs and the total density of façades are factors of significant weight on predictions. The results also emphasize the importance of façade thickness and the total density of the clustered exterior layers.
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| 3. |
- Barack, Leor, et al.
(author)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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In: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Research review (peer-reviewed)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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| 4. |
- Eddin, Mohamad Bader, et al.
(author)
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A comparison of numerical approaches to quantify sound insulation of lightweight wooden floor structures
- 2022
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In: Internoise 2022 - 51st International Congress and Exposition on Noise Control Engineering. - 9781906913427
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Conference paper (peer-reviewed)abstract
- Quantifying air-borne and structure-borne sound insulation is an important design consideration for the indoor comfort in a building. Although sound insulation performance is commonly measured experimentally, numerical methods can have time-saving and economic benefits. Further, numerical methods can be incorporated within building simulations to provide an estimate of the acoustic environment. In response, this paper evaluates three different computational approaches for quantifying sound insulation in one-third octave bands (50 Hz -5 kHz) of a lightweight floor including: an analytical (theoretical) model, a finite element model (FEM), and an artificial neural network (ANN) model. The three numerical methods are tested on the sound insulation of a cross laminated timber (CLT) floor. The results of this study show that the ANN model is able to accurately predict the air-borne and impact sound insulation performance at frequencies above 250 Hz, but over-predicts the air-borne performance and under-predicts the impact performance at low frequencies. However, the analytical and FEM strategies provide acceptable estimations, useful during the conceptual design stage, but with higher deviations than ANN model across all frequencies. While no model is able to accurately represent acoustic behavior across all frequencies, this work highlights the advantages and disadvantages when applied to predicting the sound insulation of a CLT floor.
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| 5. |
- Eddin, Mohamad Bader, et al.
(author)
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Prediction of Sound Insulation Using Artificial Neural Networks—Part I : LightweightWooden Floor Structures
- 2022
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In: Acoustics. - : MDPI AG. - 2624-599X. ; 4:1, s. 203-226
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Journal article (peer-reviewed)abstract
- The artificial neural networks approach is applied to estimate the acoustic performance for airborne and impact sound insulation curves of different lightweight wooden floors. The prediction model is developed based on 252 standardized laboratory measurement curves in one-third octave bands (50-5000 Hz). Physical and geometric characteristics of each floor structure (materials, thickness, density, dimensions, mass and more) are utilized as network parameters. The predictive capability is satisfactory, and the model can estimate airborne sound better than impact sound cases especially in the middle-frequency range (250-1000 Hz), while higher frequency bands often show high errors. The forecast of the weighted airborne sound reduction index Rw was calculated with a maximum error of 2 dB. However, the error increased up to 5 dB in the worse case prediction of the weighted normalized impact sound pressure level Ln,w. The model showed high variations near the fundamental and critical frequency areas which affect the accuracy. A feature attribution analysis explored the essential parameters on estimation of sound insulation. The thickness of the insulation materials, the density of cross-laminated timber slab and the concrete floating floors and the total density of floor structures seem to affect predictions the most. A comparison between wet and dry floor solution systems indicated the importance of the upper part of floors to estimate airborne and impact sound in low frequencies.
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| 6. |
- Eddin, Mohamad Bader, et al.
(author)
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Sound insulation of lightweight wooden floor structures : ANN model and sensitivity analysis
- 2022
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In: Internoise 2022 - 51st International Congress and Exposition on Noise Control Engineering. - 9781906913427
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Conference paper (peer-reviewed)abstract
- The study aims to develop an artificial neural networks (ANN) model to estimate the acoustic performance for airborne and impact sound insulation curves of different lightweight wooden floors. The prediction model is developed using 252 standardized laboratory measurement curves in one-third octave bands (50 − 5000 Hz). Each floor structure has been divided into three parts in the database: upper, main and ceiling parts. Physical and geometric characteristics (materials, thickness, density, dimensions, mass, and more) are used as network parameters. The results demonstrated that the predictive ability of the model is satisfactory. The forecast of the weighted airborne sound reduction index Rw was calculated with a maximum error of 2 dB. However, it is increased up to 5 dB in the worst case prediction of the weighted normalized impact sound pressure level Ln,w. A sensitivity analysis explored the essential parameters on sound insulation estimation. The thickness and the density of upper and main parts of the floors seem to affect estimations the most in all frequencies. In addition, no remarkable attribution has been found for the thickness and density of the ceiling part of the structures.
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| 7. |
- Nilsson, Erik, et al.
(author)
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Acoustical Treatments on Ventilation Ducts through Walls : Experimental Results and Novel Models
- 2022
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In: Acoustics. - : MDPI AG. - 2624-599X. ; 4:1, s. 276-296
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Journal article (peer-reviewed)abstract
- Sound reduction is complex to estimate for acoustical treatments on ventilation ducts through walls. Various acoustical treatments are available for ventilation ducts, including internal lining (absorption along the inner perimeter), external lagging (external sound insulation), silencer, and suspended ceilings. Previous studies have examined how silencers and the internal lining affect the sound transmission of ventilation ducts. However, there are few theories to predict the effect of external lagging in combination with ventilation ducts and how the total sound reduction is affected. This article aims to investigate different acoustical treatments and develop theoretical models when external lagging with stone wool is used to reduce flanking sound transmission via the surface area of ventilation ducts. Theoretical models are developed for external lagging and compared with measurement data. Measurements and theory are generally in good agreement over the third-octave band range of 100–5000 Hz. The developed models clarify that the distance closest to the wall has the main impact on sound reduction for a combined system with a wall and a ventilation duct. Suspended ceilings and silencers are found to be enough as acoustical treatments for certain combinations of ventilation ducts and walls. However, external lagging seems to be the only effective solution in offices and schools when a large ventilation duct passes through a wall with high sound reduction.
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| 8. |
- Nilsson, Erik, et al.
(author)
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Effect of Bearing Direction and Mounting Techniques on Cross-Laminated Timber Elements in the Field
- 2022
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In: Internoise 2022 - 51st International Congress and Exposition on Noise Control Engineering. - 9781906913427
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Conference paper (peer-reviewed)abstract
- Vibration reduction index (Kij ) measurements in the field have some challenges compared to laboratory measurements. Firstly, the measurement requires access to a construction site during the short time span when the cross-laminated timber (CLT) elements are apparent. Secondly, building contractors are often on a tight time schedule. Therefore, it is important to find a solution that minimizes the measurement time on site. Moreover, Kij measurements in the field include several types of junctions with different bearing directions which may be of importance. This paper aims to evaluate two different mounting techniques with accelerometers on CLT elements and to discuss how the bearing direction could affect the vibration level difference of junctions. Measurement data indicate few deviations between mounting techniques with bee wax or double-sided adhesive tape when accelerometers are attached to CLT elements. Furthermore, field measurements indicate that the vibration level will decrease with increased lamellas over the same CLT element. Double-sided adhesive tape is an adequate substitute for bee wax in the field for mounting accelerometers on CLT elements, with some limitations at high frequencies. Measurement data concludes that the bearing direction of CLT elements can influence the vibration reduction index of a junction.
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| 9. |
- Nilsson, Erik, et al.
(author)
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Effects of Building Height on the Sound Transmission in Cross-Laminated Timber Buildings—Vibration Reduction Index
- 2023
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In: Buildings. - : MDPI. - 2075-5309. ; 13:12
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Journal article (peer-reviewed)abstract
- High-rise wooden buildings are increasing in popularity, and they typically include cross-laminated timber in the structure. Taller buildings result in higher loads on the junctions lower down in the building, which are suggested in the literature to negatively affect the sound insulation. This study involved measurement of the vibration reduction index in four different CLT buildings, varying in height and junction details. A total of 12 junctions were measured at both high and low levels in the buildings. Among these, 10 junctions had resilient interlayers with different stiffnesses dependent on the designed quasi-permanent load, while 2 junctions lacked resilient interlayers. The results indicated that the vibration reduction index decreases lower down in the building mainly for the Wall–Wall path. The findings were consistent for all measured junctions above 400 Hz for the Wall–Wall path and for the majority of the measurements of the remaining frequency range, 400 Hz and below. The observed difference in the vibration reduction index could significantly impact the final result if a high-rise building has several flanking paths that affect the sound insulation between two apartments, and this needs to be considered during the design phase. Similar effects were shown for buildings both with and without resilient interlayers in the junctions.
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| 10. |
- Nilsson, Erik, et al.
(author)
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Sound Reduction of Ventilation Ducts through Walls : Experimental Results and Updated Models
- 2021
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In: Acoustics. - : MDPI AG. - 2624-599X. ; 3:4, s. 695-716
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Journal article (peer-reviewed)abstract
- Ventilation ducts can have a negative effect on the sound reduction index between two rooms if they pass through the dividing structure without treatments. The overall sound reduction of a ventilation duct is dependent on several factors including the transmission loss when sound is breaking in and out from the duct. This study aims to model the sound reduction of a combined system with a separating wall and a ventilation duct through it. Three walls, characterized according to ISO 717-1, are combined with three different ventilation ducts, two circular and one rectangular with different dimensions. Laboratory measurement data are used to determine the sound reduction of the different configurations and the type of treatments needed for each configuration. A proposed model with existing theory for describing sound transmission losses of circular and rectangular ventilation ducts predicts the shape of the measurement data for many frequency bands. A new theory part is developed through an iterative process for circular ducts, which is based on measurements with previous methods and studies as a guide because the existing prediction scheme is somewhat perplexing. For rectangular ducts, the existing theory has been updated to better match measurement data. The application of the proposed theory and model in this article shows similar results when compared to measurements. The difference in weighted sound reduction index between developed theories and measurement data is 0–1 dB for every configuration.
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| 11. |
- Qian, Cheng, et al.
(author)
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Calibration of the ISO tapping machine for finite-element prediction tool on a wooden-base floor
- 2019
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In: Building Acoustics. - 1351-010X. ; 26:3, s. 157-167
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Journal article (peer-reviewed)abstract
- One important challenge of the wooden constructions is to achieve a high quality of acoustic insulation, especially decreasing the impact noise in the low-frequency range. In order to avoid over-designed solutions and expensive experimental tests in the design phase, reliable prediction tools are called for. This article is an initial investigation of modeling the ISO standardized tapping machine on a cross-laminated timber floor, using finite element method. The wooden-based floor was first calibrated in terms of its dynamic properties. The influence of the material properties of the cross-laminated timber floor was discussed. The force generated by the tapping machine was then introduced in the established cross-laminated timber model. The model was finally validated by comparing the simulation results with the measured accelerations.
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| 12. |
- Qian, Cheng, et al.
(author)
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Description and calibration of the ISO tapping machine in numerical impact sound predictive tools
- 2018
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In: 47th International Congress and Exposition on Noise Control Engineering (INTERNOISE 2018). - 9781510873032
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Conference paper (peer-reviewed)abstract
- One of the challenges in wooden constructions is to be able to achieve a good acoustic insulation especially in the low frequency range. The prediction of acoustic performance of wooden buildings before erection becomes important and reliable predictive tools are in great need. To that end, the first question that arises is how to accurately model the excitation source which generates the structure-borne sound. Regarding the impact sound insulation performance of floors, the ISO 717–2 employs the tapping machine as standardised source. Although some investigations have been carried out in recent years aiming at analytically describing the tapping machine as well as modelling it, no satisfactory agreements between modelled and simulated results were achieved. In the investigations reported here, the extension of an existing frequency–domain method to include the tapping machine into finite element predictive tools is presented. Different parametric studies were carried out to investigate how different uncertainties influence the accuracy of the results. Before that, experimental tests on a CLT slab were performed to calibrate the numerical model.
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| 13. |
- Qian, Cheng, et al.
(author)
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Development of a vibroacoustic stochastic finite element prediction tool for a CLT floor
- 2019
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In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 9:6
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Journal article (peer-reviewed)abstract
- Low frequency impact sound insulation is a challenging task in wooden buildings. Low frequency prediction tools are needed to access the dynamic behavior of a wooden floor in an early design phase to ultimately reduce the low frequency impact noise. However, due to the complexity of wood and different structural details, accurate vibration predictions of wood structures are difficult to attain. Meanwhile, a deterministic model cannot properly represent the real case due to the uncertainties coming from the material properties and geometrical changes. The stochastic approach introduced in this paper aims at quantifying the uncertainties induced by material properties and proposing an alternative calibration method to obtain a relative accurate result instead of the conventional manual calibration. In addition, 100 simulations were calculated in different excitation positions to assess the uncertainties induced by material properties of cross-laminated-timber A comparison between the simulated and measured results was made in order to extract the best combination of Young's moduli and shear moduli in different directions of the CLT panel.
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| 14. |
- Qian, Cheng, et al.
(author)
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Development of stochastic finite prediction element model for CLT floors
- 2019
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Conference paper (other academic/artistic)abstract
- One of the important challenges for wooden construction is to assure good sound insulation in low-frequency range. To that end, it is important to establish reliable prediction tools to reduce the number of experimental tests and the costs. The study reported here is a first investigation aiming at developing a reliable numerical model to predict the vibration behavior of a cross-laminated timber (CLT) floor in low-frequency range. More specifically, and in order to give more meaningful and useful inputs, stochastic simulations were applied to the CLT finite-element (FE) model, in using the measurement data as the canonical reference. A comparison between the conventional manual calibration and the stochastic calibration by tuning the material properties of the target modeling was subsequently made to evaluate the performance of the stochastic method employed. It was shown that this stochastic method gives an alternative to mimic the dynamic behavior of wooden construction elements without tedious manual calibrations when the data base of the material properties is missing. Meanwhile, the stochastic method included in the FE model also allows to take into account the uncertainties of the wooden materials which are not always under control because of the diversity and nature of wood.
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| 15. |
- Wang, Jason J., et al.
(author)
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Keck/NIRC2 L'-Band Imaging of Jovian-Mass Accreting Protoplanets around PDS 70
- 2020
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In: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 159:6
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Journal article (peer-reviewed)abstract
- We present L'-band imaging of the PDS 70 planetary system with Keck/NIRC2 using the new infrared pyramid wave front sensor. We detected both PDS 70 b and c in our images, as well as the front rim of the circumstellar disk. After subtracting off a model of the disk, we measured the astrometry and photometry of both planets. Placing priors based on the dynamics of the system, we estimated PDS 70 b to have a semimajor axis of au and PDS 70 c to have a semimajor axis of au (95% credible interval). We fit the spectral energy distribution (SED) of both planets. For PDS 70 b, we were able to place better constraints on the red half of its SED than previous studies and inferred the radius of the photosphere to be 2–3 R Jup. The SED of PDS 70 c is less well constrained, with a range of total luminosities spanning an order of magnitude. With our inferred radii and luminosities, we used evolutionary models of accreting protoplanets to derive a mass of PDS 70 b between 2 and 4 M Jup and a mean mass accretion rate between 3 × 10−7 and 8 × 10−7 M Jup/yr. For PDS 70 c, we computed a mass between 1 and 3 M Jup and mean mass accretion rate between 1 × 10−7 and 5 × 10−7 M Jup/yr. The mass accretion rates imply dust accretion timescales short enough to hide strong molecular absorption features in both planets' SEDs.
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