| 1. |
- Forssén, Jens, 1968, et al.
(author)
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Toolbox from the EC FP7 HOSANNA project for the reduction of road and rail traffic noise in the outdoor environment
- 2014
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In: Transport Research Arena 2014, Paris, France. ; , s. 10-
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Conference paper (peer-reviewed)abstract
- This paper offers a brief overview of innovative methods for road and rail traffic noise reduction between sourceand receiver. These include using new barrier designs, planting of trees, treatments of ground and road surfacesand greening of building façades and roofs using natural materials, like vegetation, soil and other substrates incombination with recycled materials and artificial elements. The abatements are assessed in terms of numericallypredicted sound level reductions, perceptual effects and cost–benefit analysis. Useful reductions of noise fromurban roads and tramways are predicted for 1-m-high urban noise barriers and these are increased by addinginter-lane barriers. A 3 m wide 0.3 m high lattice ground treatment, a carefully planted 15-m-wide tree belt andreplacing 50 m of paved areas by grassland are predicted to give similar reductions. Tree belts are shown to bevery cost-effective and combining tall barriers with a row of trees reduces the negative impact of wind. Greenroofs may significantly reduce the noise at the quiet side of buildings.
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| 2. |
- Forssén, Jens, 1968, et al.
(author)
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Åtgärder i utomhusmiljön för att minska buller från väg- och tågtrafik – resultat från EU-projektet HOSANNA
- 2013
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In: LjudBladet, Svenska akustiska sällskapet. - 1403-2317. ; 3, s. 16-28
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Journal article (other academic/artistic)abstract
- Denna artikel ger en kort översikt av bulleråtgärder, resulterande från EU-projektet HOSANNA, för minskning av buller från väg- och spårtrafik under ljudets utbredning. Dessa verktyg inkluderar användning av ny skärmdesign, plantering av träd, förbättringar av mark- och vägytor samt vegetation på byggnadsfasader och tak, med hjälp av naturmaterial, såsom vegetation, jord och andra substrat i kombination med återvunnet material och artificiella element. De akustiska insättningsdämpningarna bedöms genom numeriska beräkningar, perceptuella effekter och kostnadsnyttoanalys. En betydande minskning av buller från väg- och spårtrafik förutsägs för ett 1-m-högt urbant bullerskydd. Detta kan förbättras, upp till ca 10 dB insättningsdämpning, genom att placera ytterligare skydd mellan körfälten. Ett 3 m brett och 0,3 m högt rutnät, ett omsorgsfullt planterat 15 m brett trädbälte samt att ersätta 50 meter asfalterad mark med gräsmark förutspås ge bullerminskningar om 5–8 dB, medan användning av fasadvegetation och gröna tak kan minska nivån på innergårdar med upp till ca 4 respektive 7 dB. Trädbälten visar sig vara mycket kostnadseffektiva och kombinationer av höga skärmar med en rad av träd minskar de negativa effekterna av vind på bullerskärmars insättningsdämpning. Gröna tak kan minska bullret på den tysta sidan av byggnader.
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| 3. |
- Nilsson, Mats, et al.
(author)
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NOVEL SOLUTIONS FOR QUIETER AND GREENER CITIES
- 2013
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Reports (other academic/artistic)abstract
- This brochure summarizes the main findings of the research project “HOlistic and Sustainable Abatement of Noise by optimized combinations of Natural and Artificial means” (HOSANNA). The project aimed to develop a toolbox for reducing road and rail traffic noise in outdoor environments by the optimal use of vegetation, soil, other natural materials and recycled materials in combination with artificial elements.
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| 4. |
- Forssén, Jens, 1968, et al.
(author)
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Initial results for traffic noise mitigation with Helmholtz resonators in the ground surface beside a road
- 2013
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In: 42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013. - 9781632662675 ; 3, s. 2345-2352
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Conference paper (peer-reviewed)abstract
- For reduction of road traffic noise, measures focussing on the propagation path are needed as complements to measures at source. Here, the effect of Helmholtz resonators, buried in the ground surface alongside the road, is investigated. Possible benefits of buried resonators are that they can function without obstructing the accessibility to the protected area. A modelling approach using equivalent sources is described for a coupled field of resonators in an otherwise acoustically hard ground plane. The model is validated in comparison with laboratory measurements. For selected road traffic cases, the model is used to predict the effect of resonators in a grid pattern within a strip along the road, showing noise reductions of 2-4 dBA.
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| 5. |
- Forssén, Jens, 1968, et al.
(author)
-
Porous ground, crops, and buried resonators
- 2014
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In: Environmental Methods for Transport Noise Reduction. - : CRC Press. - 9781482288773 ; , s. 153-176
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Book chapter (other academic/artistic)abstract
- Transport noise travelling near to naturally occurring porous ground surfaces, such as grassland, is reduced at frequencies relevant to noise control as the result of interference between direct and groundreflected sound known as the ground effect. Although it is observed frequently that different types of naturally occurring ground surfaces give rise to different ground effects, little thought has been given to deliberately choosing ground to give an improved noise reduction. In this chapter, results of calculations and measurements are provided that can inform this choice. Dense vegetation, in the form of ground cover or crops, contributes to ground effect as a result of the penetration of roots into soil and adds extra attenuation due to scattering by leaves and stems. Calculations are provided that suggest the potential usefulness for noise control of certain combinations of ground and crops. Experiments and calculations are reported showing that ground that is otherwise acoustically hard, such as nonporous asphalt or concrete, can be altered to be more effective for noise reduction by being made porous or by inserting porous strips or patches composed, for example, from gravel. Porous asphalt road surfaces are used to reduce both noise generation and propagation from road–tyre interaction. Their effectiveness for reducing traffic noise can be increased by burying preformed resonating chambers. Resonators also can be buried in hard or porous ground to reduce noise. Laboratory data and predictions are presented that demonstrate the usefulness of this method.
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| 6. |
- Maennel, M., et al.
(author)
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Improving the acoustic performance of low noise road surfaces using resonators
- 2013
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In: Proceedings of Meetings on Acoustics (21th international congress on acoustics, ICA). - : ASA. - 1939-800X. ; 19, s. 1-9
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Conference paper (peer-reviewed)abstract
- Road surfaces made of porous asphalt are widely used to reduce the tire-road-noise generated during the rolling process of passenger cars and trucks. As the engine noise was reduced significantly in the last decades the tire-road-noise is the main sound source for driving speeds of 40 kmph (25 mph) and higher for passenger cars. This means that low noise road surfaces may not only be used on highways but also on inner-city main roads to generate a significant reduction on traffic noise. However, the acoustic performance of road surfaces made of porous asphalt is limited as a result of the trade-off between acoustic properties and road surface durability. By including resonators e.g. of Helmholtz type in the porous road surface it is possible to improve its absorbing performance without loss in durability. The paper describes recent research activities on such resonators in porous road surfaces made in the European project HOS ANN A. The acoustic properties in terms of insertion loss have been calculated for different arrays of resonators. Measurements on realized porous road surfaces including resonators were carried out. The results show that resonators can improve the acoustic performance of porous road surfaces substantially. © 2013 Acoustical Society of America.
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| 7. |
- van der Aa, Bart, 1985, et al.
(author)
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Artificial refraction of sound propagating outdoors by a sonic crystal noise barrier with increasing cylinder diameter over height
- 2012
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In: Proceedings - 9th European Conference on Noise Control, EURONOISE 2012, Prague, 10-13 June 2012. - 2226-5147. - 9788001050132 ; , s. 938-943
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Conference paper (peer-reviewed)abstract
- Upward refraction of sound propagating outdoors by a finite set of two-dimensional cylinders has been studied in the homogenization region. All cylinders in the field are located above a ground plane and have their longitudinal axes orientated parallel to the ground. By increasing the cylinder radius with height, a medium is created which effective sound speed decreases over height. With a decreasing sound speed profile a cylindrical wave propagating inside such a structure can be refracted upwards, consequently creating a shadow zone behind the object. Acoustic phenomena for continuous graded index media (GRIN CM), predicted using the Finite Element Method (FEM), are demonstrated. Using modified homogenization formulas the results are then matched with a qualitatively equivalent graded index sonic crystal (GRIN SC), predicted with Multiple Scattering Theory (MST). In order to gain a reasonable insertion loss the barrier thickness must be chosen in accordance with the wavelength of the incoming field and should be in the order of a few wavelengths. Furthermore, it has been shown that the performance of these refractive structures is determined by the shape of the effective sound speed profile in relation to the point of excitation.
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| 8. |
- van der Aa, Bart, 1985
(author)
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Graded index sonic crystal noise barriers: An introduction to design and optimization
- 2012
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Licentiate thesis (other academic/artistic)abstract
- Environmental noise pollution and its impact on human beings remains to be an important topic in acoustics. Conservative estimations of the World Health Organization have shown that traffic related noise alone causes a loss of approximately one million healthy life years, only within Western Europe. Broad selections of noise control devices to attenuate road traffic noise during propagation are available. Still, traditional noise barriers are most commonly used, but alternative solutions exist. A solution with great potential is to place periodic arrangements of cylinders in between the source and the receiver, often referred to as sonic crystal (SC) noise barriers. Generally, there are two important frequency regimes when using a SC, i.e. the region below and above the lowest band gap frequency. In the high-frequency limit sound may be attenuated due to pass-stop behaviour, which translates to whether the structure supports acoustic wave propagation through it or not. The frequency limit near and above the first band gap attracted considerable attention. However, studies on phenomena well below the lowest band gap frequency, where sound may be redirected or focussed into a certain direction, are less common. One aim of this thesis is to introduce, and numerically demonstrate, a SC noise barrier that gains in broadband noise reduction by upward refraction of sound propagating through the structure. Alternatively, one could see a device with such properties as a broadband acoustic lens, since it will focus incoming waves into a distinct direction, for a broad range of frequencies. An upward refracting medium, or broadband acoustic lens, is created by orienting cylinders parallel to the ground surface and increasing the cylinder radius as a function of height, i.e. a graded index sonic crystal (GRIN SC). The study is restricted to a two-dimensional semi-infinite space, bounded by a hard reflecting ground surface. A beneficial aspect of GRIN SC barriers, compared to SC barriers with vertically oriented scatterers, is that it can simultaneously benefit from stop-band and focussing phenomena. Optimization of the broadband noise reducing performance of GRIN SC barriers placed in a realistic but simplified outdoor road traffic situation is also presented. To do this, a method is introduced, which iteratively creates complex cylinder formations using a genetic algorithm. Calculated results show that (i): by properly selecting the number of scatterers per wavelength a GRIN SC noise barrier is well approximated by homogenization techniques in the low-frequency regime and (ii): a combination of upward refraction and stop-bands contribute to broadband noise reduction of GRIN SC structures.
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| 9. |
- van der Aa, Bart, 1985, et al.
(author)
-
Numerical comparison of traditional noise screens and refractive graded index sonic crystal noise barriers in downwind sound propagation
- 2012
-
In: Proceedings of the 41st International Congress and Exposition on Noise Control Engineering (InterNoise 2012), 19-22 August 2012, New York City, NY, USA. - 9781627485609 ; 9, s. 7183-7189
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Conference paper (peer-reviewed)abstract
- Sound propagation over a traditional noise screen in downwind conditions is numerically investigated and compared with a graded index sonic crystal (GRIN SC) noise barrier. The latter type of noise barrier creates a shadow zone by upward refraction of waves propagating through. Upward refraction is here achieved by varying the cylinder radius with height hence creating a graded index medium which effective sound speed varies accordingly. Contrary to GRIN SC noise barriers, traditional noise screens aim at improving the sound environment by screening sound emanating from, e.g. traffic noise sources. It has been shown that in downwind propagating conditions traditional solid screens introduce large wind speed gradients above the barrier top, which may give rise to downward refraction of acoustic waves into the shadow zone. In two-dimensional space, wind speed profiles of a traditional screen and an acoustically equivalent GRIN SC noise barrier are numerically computed using computational fluid dynamics. The modeled background flow, treated as an effective sound speed, is then used as input parameter for acoustic propagation calculations. The acoustic performance of both structures including a non-uniform background flow has been evaluated for a simple outdoor setup assuming a hard reflecting ground surface and a single noise source.
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| 10. |
- van der Aa, Bart, 1985
(author)
-
Road traffic noise reduction by multiple scattering and absorption mechanisms
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- Millions of people in Europe, and even more on a global scale, are affected by environ- mental noise. Traffic related noise is estimated to cause a yearly loss of approximately one million healthy life years in Western Europe, which is mostly related to road traffic noise. To reduce road traffic noise during propagation traditional noise barriers are mostly used. However, these structures are often visually opaque, bulky, and therefore typically not ap- plicable in city-centres or other urban areas. The main goal of this thesis is to study noise barriers that blend well in the urban landscape and are suitable to protect pedestrians, cyclists, and other outdoor receivers, from road traffic noise.A potential solution to meet those requirements is based on the idea to place an array of cylindrical scatterers between a source and a receiver. These structures, known as sonic crystals (SCs), reduce noise at a receiver due to a multiple scattering process and can be engineered to specific needs by modifying the cylinder formation or the scatterers. The acoustic properties of a SC can be divided into two main frequency intervals: (i) where wavelengths are much larger than the periodic length of the structure, and (ii) where wavelengths are in the order of the periodic length of the structure, or shorter. In this thesis, an array of cylinders parallel to the ground surface is studied, which due to the orientation can be designed to exhibit focussing properties in the long-wavelength re- gion, but simultaneously can utilise band-gap phenomena at shorter wavelengths. These structures, referred to as graded index sonic crystal (GRIN SC) noise barriers, have been optimised for an idealised two-dimensional outdoor configuration. To facilitate further improved SC barrier designs, scattering by an array of perforated cylinders with porous cores is studied in the framework of Multiple Scattering Theory (MST). Predictions and measured data show that a substantial noise reduction is possible in a wide frequency range. To simulate point source scattering by a cross-sectionally invariant array of rigid cylinders in a three-dimensional domain, the 2.5-dimensional Multiple Scattering Theory (2.5D MST) is introduced. Numerical predictions based on the 2.5D MST model show that the characteristic frequency response of a GRIN SC shifts up in frequency during a typical vehicle pass-by scenario, which will lower the global efficiency of the device. A SC noise barrier placed perpendicular to an impedance surface is also studied using 2.5D MST. The noise reducing performance of a SC may even improve for a vehicle pass- by scenario, and therefore seems to be a better candidate to mitigate surface transport noise. In addition, a conventional low-height barrier with porous covers is investigated, which is a simple, yet effective, alternative to the cylinder based structures.
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