| 1. |
- 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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| 2. |
- 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
-
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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| 3. |
- Genell, Anders, 1974-, et al.
(author)
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Impact of railroad switches on rail noise exposure near stations
- 2022
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In: Internoise 2022. - : The Institute of Noise Control Engineering of the USA, Inc.. - 9781906913427
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Conference paper (peer-reviewed)abstract
- According to Common NOise aSSessment methOdS in EUrope (CNOSSOS-EU) in Annex II of Directive 2002/49/EC, noise from road, rail and airplane traffic, as well as noise from industries, shall be assessed using this common method. For railway noise in Sweden, noise assessment has previously been done using the Nordic Assessment Method for Train Noise, revised 1996 (NMT96). NMT96 includes a simple correction for rail joints of +3dB and for rail switches of +6dB. CNOSSOS-EU instead introduces a speed dependent correction based on a third octave band wavelength spectrum adding up to 20dB rolling noise energy in lower frequencies and down to -40 dB in higher frequencies. Measurements recently performed for two different rail switch types along the Swedish rail system indicate that the frequency distribution corresponds well to the CNOSSOS-EU correction for one type of rail switch but not for the other, and for the overall level difference the opposite is true. In order to investigate to what extent this deviation is affecting noise exposure an inventory of more than 12000 rail switches along the Swedish railroad network has been performed to identify what types are situated in densely populated areas such as railway stations.
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| 4. |
- 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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