| 1. |
- Arvidsson, Emma, et al.
(författare)
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Optimization of sound absorbing ceilings
- 2018
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Ingår i: 47th International Congress and Exposition on Noise Control Engineering (INTERNOISE 2018). - 9781510873032
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Konferensbidrag (refereegranskat)abstract
- The typical acoustical treatment in ordinary rooms such as classrooms, offices, conference rooms etc is an absorbing suspended ceiling. Due to the non-uniform distribution of the absorbing material the sound field at steady-state and during sound decay is far from the ideal conditions assumed in the diffuse field theory. Especially during the sound decay, the degeneration of the sound field emphasizes the shortcomings of the diffuse field assumption. On the other hand, the absorbing properties of sound absorbing ceilings are determined under diffuse field conditions according to the standard ISO 354. The outcome of this measurement in the form of an absorption coefficient is often used as input data in calculation or simulation models. This means that the absorbing properties of the ceilings are characterized under circumstances that are hardly ever encountered in practice. The directional scattering effect of furniture and other interior objects is another circumstance that has to be considered to understand the interaction between the absorbing ceiling and the sound field in rooms with ceiling treatment. In this paper the outline of a project is presented that deals with how to optimize the acoustical properties of ceilings in order to achieve certain room acoustic target values related to reverberation time, speech clarity and sound strength.
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| 2. |
- Autio, Hanna, et al.
(författare)
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A statistical method for parameter estimation from Schroeder decay curves
- 2018
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Ingår i: 47th International Congress and Exposition on Noise Control Engineering (INTERNOISE 2018) : Impact of Noise Control Engineering - Impact of Noise Control Engineering. - 9781510873032
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The sound decay curve, measured by either the interrupted noise method or the Schroeder method, can provide relevant information pertaining to a room’s acoustical properties. However, the relevant information is not always readily extractable from the measurements. In this study, measurements of the decay curves of the historically important Vadstena Abbey church in Sweden have been obtained using both of the classical methods. The test building was in normal use with high levels of background noise during the measurements. Aline-fit analysis showed a trend where the Schroeder decay curves yielded a longer estimated reverberation time compared to the interrupted noise method for low frequencies. This indicates that the measurement results are affected by background noise. A statistical model was developed for the Schroeder decay curve in such circumstances. Using it, the maximum likelihood estimates for the deterministic decay parameters can be found even when there are multi-slope decay patterns or significant background noise. The model is straight-forward to implement and can find an estimate for a single-slope decay also when some commercial software fails. The performance for double-slope decay models, as well as a comparison to the results from the interrupted noise method, are analyzed.
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| 3. |
- Qian, Cheng, et al.
(författare)
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Description and calibration of the ISO tapping machine in numerical impact sound predictive tools
- 2018
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Ingår i: 47th International Congress and Exposition on Noise Control Engineering (INTERNOISE 2018). - 9781510873032
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Konferensbidrag (refereegranskat)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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