| 1. |
- Zieliński, Tomasz G., et al.
(författare)
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Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies : Round robin study
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier B.V.. - 2214-8604 .- 2214-7810. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials.
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| 2. |
- Wei, Weigang, et al.
(författare)
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Urban background noise mapping : The general model
- 2014
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Ingår i: Acta Acoustica united with Acustica. - 1610-1928 .- 1861-9959. ; 100:6, s. 1098-1111
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Tidskriftsartikel (refereegranskat)abstract
- Surveys show that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. However, current practice in noise prediction often underestimates the noise levels at a shielded façade. Multiple reflections between façades in street canyons and inner yards are commonly neglected and façades are approximated as perfectly flat surfaces yielding only specular reflection. In addition, sources at distances much larger than normally taken into account in noise maps might still contribute significantly. Since one of the main reasons for this is computational burden, an efficient engineering model for the diffraction of the sound over the roof tops is proposed, which considers multiple reflections, variation in building height, canyon width, façade roughness and different roof shapes. The model is fitted on an extensive set of full-wave numerical calculations of canyon-to-canyon sound propagation with configurations matching the distribution of streets and building geometries in a typical historically grown European city. This model allows calculating the background noise in the shielded areas of a city, which could then efficiently be used to improve existing noise mapping calculations. The model was validated by comparison to long-term measurements at 9 building façades whereof 3 were at inner yards in the city of Ghent, Belgium. At shielded façades, a strong improvement in prediction accuracy is obtained.
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