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On the choice between walls and berms for road traffic noise shielding including wind effects
Abstract
A numerical comparison is made between the road traffic noise shielding provided by 4-m high vertically erected walls and (earth) berms, averaged over large zones behind them. A previously developed and validated full-wave numerical sound propagation model was used. In absence of wind, a noise screen is preferred when it can be placed at the same position as the foot of the berm at the source side. In case of a fixed top position for both the wall and berm, an acoustically soft berm with a flat top gives similar shielding as the wall. In case of downwind sound propagation (i.e. a worst-case situation), the noise wall efficiency largely decreases. Strong wind might lead to an almost complete loss of noise wall shielding when compared to sound propagation over unobstructed terrain in absence of wind. In contrast, with decreasing berm slope angle, downward refraction by wind can become very small. In case of berms with a slope of 1:3, or berms with steeper slopes but with a flat top, the averaged wind effect can be smaller than 1 dBA because of the limited magnitude of vertical gradients in the horizontal component of the wind speed near such more streamlined obstacles. When looking at long-term equivalent noise levels, including periods with wind, acoustically soft and shallow berms should be chosen upon vertically erected noise walls. In addition, there are clear non-acoustical benefits associated with the use of such natural berms. Wind-breaking vegetation has not been considered in this study.
... Therefore, in the current project, the noise shielding efficiency of a number of desired measures (more precisely combinations of natural berms and vegetation scenarios) were simulated in standardized crosssections of the depressed ring road under study (see Fig. 2). Previous research showed that non-steep and acoustically soft berms could be especially interesting to abate road traffic noise (Busch, Hodgson, & Wakefield, 2003;Hutchins, Jones, & Russell, 1984;Van Renterghem & Botteldooren, 2012a, 2012b. Although this information cannot be directly transferred to each future design proposed by the planning teams, it already gives a good indication of what measures could work. ...
... An open window leads to a strong loss in acoustic insulation along that facade (Jean, 2009;Locher et al., 2018). In addition, deliberately closing windows is not a preferred coping strategy for dwellers (Van Renterghem & Botteldooren, 2012a). ...
... When dealing with exposure at dwellings, measures improving noise perception could be considered as well. The benefits of a quiet side have been largely recognized and quantified (Öhrstrom et al., 2006;Gidlöf-Gunnarsson & Öhrström, 2010;de Kluizenaar, Salomons, & Janssen, 2011;Van Renterghem & Botteldooren, 2012a). Further corrections could be made when accounting for audio-visual interactions in environmental noise perception. ...
Due to its local character, there is a tight link between the environmental noise issue and urban planning. Although the need for sound planning has been advocated since decades, limited information can be found on what this now means in practice. In this work, a methodology to internalize sound in the urban planning process is presented, applied to a major redevelopment project of a city ring road. The specific interest in increasing green infrastructure, and at the same time, tackling environmental noise, makes this project timely and challenging. Noise experts took part in an intense co-creation process with the spatial planning teams, where also dwellers were involved. Interactions ranged from conveying general information on environmental noise, providing solutions tailored to the local setting, qualitative expert opinions on initial plans, and assessing the applicability of uncommon noise abatements with numerical tools. The latter is important as the noise reduction potential of such measures could strongly influence the next round of spatial planning. Each planning phase should be optimized to allow maximum freedom in the next iterations. While evaluating various planning scenarios, separate acoustic goals were set for the sound exposure at dwellings, in the public space and along soft connections.
... An important literature exists on this subject. Less work has been done and reported on earth berms [5,6]. However, berms offer several advantages worth considering. ...
... Their efficiency is dictated by their shape, their height and their impedance. The use of berms compared to straight barriers or to combinations of both has been considered in [6,9]. For hard soils, the key parameter is the position of the diffraction point closest to traffic. ...
... In [10] a genetic algorithm is employed to optimize the shape of an earth berm placed behind a vertical rigid barrier thus keeping a diffracting edge close to the source and benefiting from a long top. Also, more complex effects occur when meteorological aspects are introduced [6,34]; for instance, downwind conditions may be favourable to shallow berms. This paper concentrates on most common situations when these effects can be neglected. ...
The reduction of traffic noise is often achieved using noise barriers or earth berms. More complex solutions have been reported making use of multiple diffraction effects (using complex or combined barriers) or roughened boundaries. Fractal-like surfaces will lead to increased absorption effects. The present paper focuses on the improvement of berms by adding different types of rugosity on its 3 sides. Using a BEM approach, several types of rugosity have been investigated either regular or irregular, simple or multi-level (fractal-like). Global efficiencies have been evaluated considering a realistic four-lane highway combining cars and lorries. In some cases, in a non-refracting atmosphere, a global reduction of 10 dB(A) relative to a smooth berm has been achieved. Effect of surface impedance, berm’s size and a comparison of 2D vs 2.5D computations are also considered.
... Typical earth berms are aerodynamically much smoother than a straight, vertical-sided noise wall. Consequently, they limit the aforementioned strong vertical gradients in the horizontal component of the wind field [41] observed near conventional noise walls. Earth berms, and especially those with a low slope angle, were predicted to be sufficiently unaffected by negative downwind effects [41]. ...
... Consequently, they limit the aforementioned strong vertical gradients in the horizontal component of the wind field [41] observed near conventional noise walls. Earth berms, and especially those with a low slope angle, were predicted to be sufficiently unaffected by negative downwind effects [41]. In case of triangular-shaped berms with a slope of 1:3, or berms with steeper slopes but with a flat top (trapezium-shaped), the averaged wind effect (loss in shielding relative to a windless situation) can be smaller than 1 dBA in road traffic noise setups, even in an extended zone up to 250 m from the road [41]. ...
... Earth berms, and especially those with a low slope angle, were predicted to be sufficiently unaffected by negative downwind effects [41]. In case of triangular-shaped berms with a slope of 1:3, or berms with steeper slopes but with a flat top (trapezium-shaped), the averaged wind effect (loss in shielding relative to a windless situation) can be smaller than 1 dBA in road traffic noise setups, even in an extended zone up to 250 m from the road [41]. ...
... A first one is the preservation of ground effects. Well designed earth mounds consisting of acoustically soft ground were measured and numerically predicted to provide at least the same amount of noise reduction as a noise wall of similar height (Busch et al., 2003;Arenas, 2008;Van Renterghem and Botteldooren, 2012). A second advantage is that a berm is less sensitive to refraction by wind. ...
... A second advantage is that a berm is less sensitive to refraction by wind. A non-steep and natural berm was predicted to outperform the shielding obtained by a noise wall in a long-term evaluation (Van Renterghem and Botteldooren, 2012). In addition, natural environments are highly preferred by people (Kaplan and Kaplan, 1989), leading to improved noise perception (for an overview, see Van Renterghem, 2018). ...
Deliberately changing terrain undulation and ground characteristics (“acoustical landscaping”) is an potential noise abatement solution near roads. However, there is hardly any research regarding the validity of sound propagation models to predict its effectiveness. Long-term continuous sound pressure level measurements near a complex road traffic and sound propagation case were performed. Three types of modeling approaches were validated, covering the full spectrum of available techniques. A two-dimensional full-wave technique (the finite-difference time-domain method, FDTD), but also an advanced engineering model (the Harmonoise point-to-point model), provide accurate transmission loss predictions, both in 1/3 octave bands and for total A-weighted sound pressure levels. Two common and widely used semi-empirical engineering methods (ISO9613-2 and CNOSSOS) yield rather inaccurate results, notwithstanding the short propagation distance. The sensitivity to input data was assessed by modeling various scenarios with the FDTD method. Detailed ground effect modeling was shown to be of main importance.
... An acoustic barrier is a structure or obstacle between the noise source and the receiver that can attenuate the sound level coming to the receiver. The basic types are acoustic screens, earth berms, gabion barriers, vegetation belts and special constructions (combination of some of the above types) (Murphy and King, 2011;Van Renterghem and Botteldooren, 2012;Koussa et al., 2013). ...
... Despite their widespread use, noise barriers have been associated with several drawbacks: the main disadvantage is their lack of effectiveness in many cases, other than visual and aesthetic issues, problems in vehicle security, snow accumulation, visibility of security, lighting, drainage, road accessibility restrictions and other environmental disadvantages (Burt, 1971;Nielsen and Solberg, 1988;Imagine Project, 2004;Baldauf et al., 2008;Hornikx and Forssén, 2009;Van Renterghem and Botteldooren, 2012). ...
... Non-steep berms strongly reduce the wind effects compared to vertically erected noise walls due to their aerodynamic shape [18]. Steep berms, on the other hand, can still lose a lot of their noise shielding under downwind conditions, although somewhat less pronounced than in case of a vertically erected noise wall with a similar height. ...
... Given the limited improvement during windy periods, scattering could be relevant when looking at the global effect. However, vegetation on a berm ensures that its surface becomes acoustically soft, which is clearly positive for sound waves diffracting over the berm [18]. The optimal canopy designs to reduce downwind effects near a single noise wall, a steep berm, and noise walls on either side of a highway are summarized in Figure 5.11. ...
This chapter provides design rules for tree/vegetation belts
along roads. The basic interactions between sound waves and the com-
ponents of a tree/vegetation belt (soil, shrubs/hedges, trunks, and cano-
pies) are discussed, and the parameters of importance identi!ed. The
use of an optimized planting scheme could turn a tree belt along a road
into an ef!cient noise-reducing measure. While, in general, one should
strive for rather high biomass densities to obtain useful noise reduction,
some interesting approaches are presented to relax such demands with-
out affecting noise shielding too much. A strip of trees also has an effect
on the stability of the lower part of the atmospheric boundary layer,
and, thus, on its refractive properties. As a consequence, an additional
positive effect is expected during the night by the presence of a tree belt,
which outperforms the slightly worsened meteorological situation dur-
ing daytime. A topic of great concern is the strong reduction in ef!ciency
of a noise wall under downwind sound propagation conditions. A row
of trees, acting as a windbreak, can recover at least part of the shielding
that was lost by the action of the wind. Design rules are provided that
are applicable for scenarios with single noise walls, noise walls on either
side of the road, and in case of steep berms. Downwind receivers at close
distance and farther away are considered.
... An acoustic barrier is a structure or obstacle between the noise source and the receiver that can attenuate the sound level coming to the receiver. The basic types are acoustic screens, earth berms, gabion barriers, vegetation belts and special constructions (combination of some of the above types) (Murphy and King, 2011;Van Renterghem and Botteldooren, 2012;Koussa et al., 2013). ...
... Despite their widespread use, noise barriers have been associated with several drawbacks: the main disadvantage is their lack of effectiveness in many cases, other than visual and aesthetic issues, problems in vehicle security, snow accumulation, visibility of security, lighting, drainage, road accessibility restrictions and other environmental disadvantages (Burt, 1971;Nielsen and Solberg, 1988;Imagine Project, 2004;Baldauf et al., 2008;Hornikx and Forssén, 2009;Van Renterghem and Botteldooren, 2012). ...
... Finally, this study demonstrates that noise pollution can penetrate hundreds of meters into protected areas and has the potential to diminish the value of natural spaces for wildlife habitat and human recreation at great distances from roads. While specific remediation efforts can help to reduce road noise, such as walls, berms, and evergreen plantings (Renterghem and Botteldooren, 2012), the construction of any roads through protected areas will invariably increase noise pollution. ...
Noise pollution can reduce the ability of urban protected areas to provide a refuge for people and habitat for wildlife. Amidst an unprecedented global pandemic, it is unknown if the changes in human activity have significantly impacted noise pollution in metropolitan parks. We tested the hypothesis that reduced human activity associated with the COVID-19 pandemic lockdowns would lead to reduced sound levels in protected areas compared with non-pandemic times. We measured sound levels in three urban protected areas in metropolitan Boston, MA (USA) at three time periods: in the fall and summer before the pandemic, immediately after the government-imposed lockdown in March 2020 when the trees were leafless, and during the beginning of reopening in early June 2020 when the trees had leaves. At all time periods, sound levels were highest near major roads and demonstrated a logarithmic decrease further from roads. At the two protected areas closest to the city center, sound levels averaged 1–3 dB lower during the time of the pandemic lockdown. In contrast, at the third protected area, which is transected by a major highway, sound levels were 4–6 dB higher during the time of the pandemic, likely because reduced traffic allowed vehicles to travel faster and create more noise. This study demonstrates that altered human levels of activity, in this case associated with the COVID-19 pandemic, can have major, and in some cases unexpected, effects on the levels of noise pollution in protected areas.
... In response to the mobilization, an experimental site composed of four vegetated earth berms bordering the carriageways had been built by the motorway company ( Figure 1). Earth berms are structures mainly built for noise abatement strategy [10]. Their impact on air pollution lessening is seldom studied [11] in contrast to that of alternative structures such as solid or vegetative noise barriers, e.g., [12][13][14][15][16][17]. ...
A test site located along a 12-lane motorway east of Montpellier, France, is used to evaluate the potential of biomagnetic monitoring on traffic-related particulate matter (PM) to parametrize a computational fluid dynamics (CFD) simulation of the local airflow. Two configurations were established on the site with three vegetated flat-top earth berms of a basic design, and a fourth one was located windward to the traffic roofed with a 4-m-high precast concrete wall. As a first step, PM deposition simultaneously on plant leaves, on low-cost passive artificial filters, and on soils was estimated from proxies supplied by magnetic and X-ray fluorescence measurements on both sides of the motorway. These latter revealed that traffic-related pollutants are present on soils samples highlighted with a clear fingerprint of combustion residues, and wears of breaks, vehicles, and highway equipment. Maximum PM accumulations were detected in the lee of the berm–wall combination, while no significant deposition was observed on both sides of the flat-top earth berms. These results are in line with measurements from PM µ-sensors operated by the regional state-approved air quality agency. Finally, we compared the experimental measurements with the outcomes of a computational fluid dynamics (CFD) modeling based on the Reynolds-Averaged Navier–Stokes (RANS) equations that consider the traffic-induced momentum and turbulence. The CFD modeling matches the experimental results by predicting a recirculated flow in the near wake of the berm–wall combination that enhances the PM concentration, whereas the flat-top berm geometry does not alter the pollutants’ transport and indeed contributes to their atmospheric dispersion.
... Los estudios de Van Renterghem y Botteldooren [75] muestran que los taludes de suelo pueden reducir, en promedio, los niveles de ruido de 11.1 dB, y las paredes pueden reducir, en promedio 7.7-8.3 dB. ...
Evaluación preliminar de los impactos ambientales asociados al Tren Maya
... In urban areas, the main source of noise originates from the widespread transportation networks spanning throughout the cities. Therefore, as the traffic is spread over the whole urban area, noise mitigation measures such as barriers [189], greenery [180], facades [155] and low-noise roads [190] are generally difficult to implement in already developed urban areas. ...
... As indicated earlier, there are a number of constraint factors for considering a given technical solution against noise as a feasible alternative, i.e. required sound-level attenuation, average speed of the traffic (Nielsen and Solberg, 1988), physical or technical conditions that might affect the implementation of a given alternative (Ellis et al., 2004), extreme weather conditions that might override any solution (Van Renterghem and Botteldooren, 2012), and the existence of previous measures against noise in the road stretch that were ineffective or that might impede the implementation of other solutions. Because of their relevance in the decision-making process, a pre-requisite evaluation scheme based on these factors was addressed prior to the multi-criteria analysis, allowing the user to rule out unfeasible technical solutions at the earliest stage. ...
... Studies by Van Renterghem and Botteldooren (2012) show that a soil verge can reduce, on average, noise levels of 11.1 dB, and walls can reduce, on average 7.7-8.3 dB. ...
In this chapter, we review the level of disturbance caused by railways due to noise and vibration, air, soil and water pollution, and soil erosion. There is evidence that soil and hydrology contamination may affect vegetation and aquatic fauna while noise can affect terrestrial vertebrates. In fact, noise, light, and vibration due to railways have been observed to reduce the abundance and richness of some insects, amphibians, and birds, and to cause avoidance behaviour on predators. Interestingly, reptiles, some bird species, small mammals, and large mammals seem to ignore rail traffic and benefit from the vegetation planted in the railway verges that provide food and shelter. Some engineering structures have been implemented to reduce the effects of railway disturbance: rail fastenings, rail dampers, under-sleeper pads, and noise barriers are applied to minimize noise and vibration; washing with water and cleaning the ballast are used to mitigate soil pollution; and grass plantation, the use of gypsum and application of compost/mulch coverage, are applied to control soil erosion.
... As indicated earlier, there are a number of constraint factors for considering a given technical solution against noise as a feasible alternative, i.e. required sound-level attenuation, average speed of the traffic (Nielsen and Solberg, 1988), physical or technical conditions that might affect the implementation of a given alternative (Ellis et al., 2004), extreme weather conditions that might override any solution (Van Renterghem and Botteldooren, 2012), and the existence of previous measures against noise in the road stretch that were ineffective or that might impede the implementation of other solutions. Because of their relevance in the decision-making process, a pre-requisite evaluation scheme based on these factors was addressed prior to the multi-criteria analysis, allowing the user to rule out unfeasible technical solutions at the earliest stage. ...
... Raising green spaces that reduce noise has been shown as an effective protection against noise. The intensity of the reduction depends on the physical properties of sound, dendrology composition, height, width, and location of green barriers in relation to the noise source and the receiver [49][50][51]. It is recommended to raise the green belt between the street and pavement width of 10-50 m, where trees and shrubs will be planted. ...
This paper evaluated exposure to road traffic noise in the city of Novi Sad, the second largest city in the Republic of Serbia. It has been investigated using analysis and systematization of the results on noise intensity in the city of Novi Sad, whether this parameter is within the approved limits for noise intensity during the day and night and whether it is in accordance with provisions of national norms of permissible noise levels in the environment, that is whether this parameter endangers people or not. In this work were used data from the Institute for Public Health of Vojvodina-Department of Residential Hygiene, which were obtained by measuring the noise intensity at 18 points in the city. Levels of noise, during the period of analysis, are usually higher than permitted and range from 1dB(A) to 8dB(A) during the day, and from 1db(A) to 9dB(A) at night. It has been determined that the noise intensity is in strong positive correlation (r(s) = 0.73) with the number of vehicles in traffic. Even though the noise intensity in the period observed has a decreasing trend, the fact that it is still higher than permitted in school and residential zones is particularly worrying. It has also been determined that traffic noise is one of the leading urban problems in the city of Novi Sad, and therefore it is necessary to implement some of the plans for protection, mentioned in the work, for its reduction.
... It is useful to investigate the acoustical performance of vegetation in street canyons using scale models. Scale models have the advantages of being unaffected by weather conditions, allowing the reproduction of various types of urban design elements, and reducing the background noise uncertainty that occurs in real field measurements [18,24]. Moreover, given the difficulty of conducting numerical analysis and evaluating the actual sound characteristics while considering the vegetation shape, scale models are appropriate for evaluating the acoustic effects of vegetation. ...
This paper proposes an evaluation procedure using a scale model to assess the noise reduction effects of vegetated façades for sustainable urban building designs. The absorption coefficients of the scale-model materials were measured to fit the absorption characteristics of real vegetation. The ground impedance of asphalt was also measured to deduce the acoustical properties of ground surfaces and to select the ground material. To assess the reduction of road traffic noise, a line source for a 1:10 scale model was modelled using ribbon tweeters that generated high frequencies ranging from 1 kHz to 40 kHz. Accordingly, the effects of adding vegetated façades were evaluated in the scale model of a street canyon. The noise reduction due to the vegetated façades was less than 2 dB at pedestrian level in a two-lane street canyon. The scale model results were compared with geometric computer simulation results, and both evaluation methods showed similar results. The suggested modelling method can be useful for evaluating the noise reduction in street canyons by vegetation considering realistic features such as the absorption, scattering, and diffraction associated with the materials and sound sources according to the shape of the vegetation.
... In this respect, wind effects near tree belts are expected to be rather limited and this could be an additional benefit. Another natural solution is applying an earth berm, which was shown to be less sensitive to the aforementioned (down)wind effect (Van Renterghem and Botteldooren, 2012a). ...
This paper discusses that a non-deep tree belt along a road can be an interesting solution to achieve road traffic noise reduction. Noise shielding is mainly obtained as a combination of multiple scattering in the tree trunk layer and due to the presence of an acoustically soft soil. A large dataset of full-wave and highly detailed numerical simulations, based as much as possible on measured input data, shows that high biomass density should be strived for as a general rule. This conflicts, however, with practical limitations regarding access to light, nutrients and water for the trees. Some interesting approaches have been identified to relax the need for high biomass density, without affecting noise shielding to an important extent. Rectangular planting schemes, where the spacing orthogonal to the road can be increased, omitting full rows parallel to the road length axis, and thinning inside the belt are examples of such measures. It is discussed that the specific choice of a planting scheme could make a tree belt along a road an efficient noise reducing measure or not.
... In critical cases, where the above measures do not suffice and sufficient space is available between the road and noise exposed homes, the proper placement of shallow and planted earth berms would be a viable, effective and also aesthetic alternative [43] to avoid noise barriers. ...
Background: The WHO-JCR has provided a general methodology to assess the health impact of environmental noise at larger scale. Switzerland used this methodology in a recent assessment. Other countries use their own assessment strategies. At smaller scales (regional, community) the application of this methodology is limited due to the use of standard exposure effect curves. In order to ensure to meet local needs (alpine valley) we adapted the methodology. Methods: We used actual GIS noise map information and merged it with GIS population information to get the number of noise exposed (30 to 70 dBA, L day , L evening and L night). On the effect side we used annoyance, sleep disturbance, hypertension and myocardial infarction. A mix of standard and regional exposure response information was applied. An upper and lower 95% confidence interval was derived for the prevalence estimates. With cost calculations we relied on the experience of the HEIMTSA-project. Results: The status quo yields high annoyance (3000-5000 persons) and high sleep disturbance (3000-4000 persons) as most important contributors. However, sleep disturbance shows the highest gain through a night curfew in truck traffic in health terms (number of affected, DALYs) and even more in health cost.
... Thus, complementary corridors of suitable grassland with the same verge width should be left beyond the road verge, parallel to the road. Raising the height of the roadside verges (similar to noise control earth berms [54]) may not only encourage owls to fly above traffic but also increase stone marten awareness of roads and traffic. Moreover, the importance of passages suggested by a previous study was not fully supported here with radio-tracking data. ...
Understanding the ecological consequences of roads and developing ways to mitigate their negative effects has become an important goal for many conservation biologists. Most mitigation measures are based on road mortality and barrier effects data. However, studying fine-scale individual spatial responses in roaded landscapes may help develop more cohesive road planning strategies for wildlife conservation.
We investigated how individuals respond in their spatial behavior toward a highway and its traffic intensity by radio-tracking two common species particularly vulnerable to road mortality (barn owl Tyto alba and stone marten Martes foina). We addressed the following questions: 1) how highways affected home-range location and size in the immediate vicinity of these structures, 2) which road-related features influenced habitat selection, 3) what was the role of different road-related features on movement properties, and 4) which characteristics were associated with crossing events and road-kills. The main findings were: 1) if there was available habitat, barn owls and stone martens may not avoid highways and may even include highways within their home-ranges; 2) both species avoided using areas near the highway when traffic was high, but tended to move toward the highway when streams were in close proximity and where verges offered suitable habitat; and 3) barn owls tended to cross above-grade highway sections while stone martens tended to avoid crossing at leveled highway sections.
Mortality may be the main road-mediated mechanism that affects barn owl and stone marten populations. Fine-scale movements strongly indicated that a decrease in road mortality risk can be realized by reducing sources of attraction, and by increasing road permeability through measures that promote safe crossings.
To investigate the influence of PAC mixture type and parameters on noise reduction performance and their variation patterns. This study investigated: the mixes’ gradation characteristics parameters, the coefficient of uniformity (CU) and coefficient of curvature (CC); the nominal maximum size (DT), the material’s composition parameter; the void ratio (VV) and thickness (H), the mixes’ structural composition parameters, and finally, the surface density (BD). PAC specimens’ sound absorption coefficient was measured indoors by the standing wave tube method, and the variation law were observed under different PAC parameters. PAC parameters’ degree of influence on noise reduction performance was investigated through grey correlation theory and correlation analysis. The results indicated that increasing the void ratio and thickness improved the peak absorption coefficient and enhanced PAC’s noise reduction performance effectively. Increasing the nominal maximum particle size weakened the noise reduction performance. In addition, the mix type and thickness had a greater influence on the basic trend in the absorption coefficient spectrogram. PAC’s noise reduction effect was reflected primarily in the middle and high frequency band, and moved to the high frequency band gradually as the thickness increased. Overall, VV, H, and DT had a relatively large effect on PAC’s noise reduction performance.
The evaluation of the effectiveness of noise barriers have addressed, in some research studies, the intrinsic characteristics of barriers, such as noise absorption or transmission; in other studies, it has been based on the global characteristics of Insertion Loss (IL), which is defined as the difference in the noise level before and after the installation of the barrier. IL is an extrinsic characteristic of noise barriers, depending largely on the site in which the barrier is placed. This research investigated the in situ effectiveness of existing noise barriers by using the indirect IL method established in the international standard ISO 10847:1997. Measurements were performed at thirty sample sites, distributed among the three most frequent types of material found on Spanish roads (earth berms and concrete and metal walls).
The results revealed moderate IL values. Results at a distance of 25 m were clearly below the expected effectiveness of a noise barrier. The IL values for the three types of barriers were similar. The best noise reduction effect was in the frequency range of 125–8000 Hz, at which the traffic noise is dominant. In most cases, the dimensions of the barriers did not seem to have been determined taking into account diffraction requirements.
Esta obra es el resultado de un esfuerzo conjunto de investigadores especiali-zados, quienes proponen soluciones a una problemática que en México lleva décadas ignorada: el impacto producido por la construcción y modernización de vías de comunicación.
La construcción y funcionamiento del Tren Maya generará impactos negativos sobre la biodiversidad de la región que pueden acumularse a los impactos de otras estructuras lineales ya existentes. Mediante la implementación de un SIG a escala 1:50,000 se identificaron, evaluaron y regionalizaron los impactos más relevantes. Con base en la evaluación de los efectos de barrera y de borde, se proponen diversas medidas de prevención y mitigación, tales como el incremento de la conectividad de la vegetación, la construcción de pasos de fauna, la reducción de ruido y vibraciones, así como modificaciones al trazo para evitar áreas críticas.
The chapters of this book bring science a little closer to the knowledge about the design, production and management of public spaces. 37 authors responded to the Project’s call to share experiences, visions and reflections on how co-creation and participatory processes can create possibilities for a sustainable and equitable future. This book intends to help researchers, governments and community leaders to move from insights to more collaborative actions.
C3Places - using ICT for Co-Creation of inclusive public Places is a project funded
under the scheme of the ERA-NET Cofund Smart Urban Futures / Call joint research programme
(ENSUF), JPI Urban Europe, https://jpi-urbaneurope.eu/project/c3places. C3Places aims at
increasing the quality of public open spaces (e.g. squares, parks, green spaces) as community
service, reflecting the needs of different social groups through ICTs. The notion of C3Places
is based on the understanding that public open spaces have many different forms and features,
and collectively add crucial value to the experience and liveability of urban areas. Understanding
public open spaces can be done from a variety of perspectives. For simplicity’s sake, and because
it best captures what people care most about, C3Places considers the “public” dimension to be
a crucial feature of an urban space. Public spaces are critical for cultural identity, as they offer
places for interactions among generations and ethnicities. Even in the digital era, people still need
contact with nature and other people to develop different life skills, values and attitudes, to be
healthy, satisfied and environmentally responsible.
The book aims to spark discussion on the co-creation of public open spaces through the active
involvement of different stakeholders in the production of a more inclusive, attractive and
responsive urban environment. It intends to help researchers, governments and drivers in
understanding and implementing more collaborative actions. The authors share experiences,
visions and reflections on how co-creation and participatory processes can open up possibilities
for a sustainable and equitable future. This book emphasises three dimensions: practice,
reflection, and learning. Practice concerns driving actions, identified and analysed experiences
that serve as key models. Reflection refers to exploring and examining the results and performances
of a co-creation process. Co-creation is not the search for a final product, but rather
a process and a new path to more responsive and inclusive communities. Learning refers to the
knowledge transfer and replication induced by the synergy of the different actors involved in
this book.
The chapters which constitute this work were completed prior to Spring 2020, so the research
and insights do not reference the global public health crisis caused by Covid-19. However,
in such challenging times the argument for co-creation approaches to increase the potential
of public spaces to support a range of inclusiveness outcomes is even stronger.
9 7 8 9 8 9 7 5 7 1 2 5 1
This publication is based upon work of C3Places Project. The C3Places Project has received funding from the
European Union’s Horizon 2020 research and innovation programme under grant agreement No 693443 and from
FCT (Portuguese Funding Agency for Science, Research and Technology).
A floresta urbana desempenha inúmeros benefícios às pessoas que vivem em cidades, dentre os quais a amenização do ruído causado pelo tráfego de veículos. Entretanto, pesquisas sobre esse benefício ainda são incipientes no Brasil. O objetivo deste trabalho foi avaliar a vegetação como atenuadora de ruído do tráfego de vias urbanas em áreas verdes de Curitiba – Paraná. A pesquisa foi realizada em dois parques de Curitiba. Utilizando-se dois decibelímetros da marca INSTRUTHERM, modelo DEC-470, em cada local de coleta foram realizadas medições simultâneas, uma na fonte do ruído à margem da avenida e outras em diferentes distâncias a partir da fonte do ruído, com 3 repetições (5 minutos de coleta, e 30 segundos de intervalo). Os resultados mostraram que o local com menor quantidade de vegetação foi o que menos bloqueou o ruído (8,3 dBeq no verão e 7,5 dBeq no inverno), enquanto o local com maior quantidade de vegetação apresentou os maiores valores de atenuação (11,8 dBeq no verão e no inverno). Apesar de haver diferença nos valores médios do bloqueio do ruído entre verão e inverno, não houve diferença estatística significativa, mesmo para as distâncias com presença de árvores caducifólias e semi-caducifólias, a qual era esperada essa diferença.
Pollution is a big issue in the Philippines. However, the country has not focused its attention towards noise pollution. This study assessed the noise intensity of a hamlet located very near the airport, where aircraft takeoffs and landings occur daily. It compares the noise intensity (in decibels) between areas with tree cover and those without. The noise intensity data were derived from recording using a mobile application, Sound Meter Pro (by Mobile Essentials), installed in two Android phones, LG G3 and Asus Zenfone Max. To avoid any bias, both phones were calibrated against a laboratory sound meter before and after field samplings and against each other, since the phones were switched between two sublocations (i.e., with tree and without tree cover). Our results showed a significant difference between sound intensities recorded in areas with (mean ± S.D.: 83.94 ± 5.51, n = 10) and without tree cover (88.14 ± 6.76, n = 10). This suggests that tree cover does reduce the amount of noise generated from aircrafts in the vicinity.
This research has a twofold environmental benefit. On the one hand, there is the recycling of a waste by-product and, on the other hand, the reduction of traffic noise pollution levels. The objective of this study is to determine and evaluate the use of a mixture of shredded palm tree pruning waste with dampened topsoil in the construction of noise barriers. With a view to efficiently recycling pruning waste and using an environmentally-friendly material which does not pose any environmental risks at the end of its useful life, the composition offering the best sound absorption has been analyzed. Based on the results obtained, a completely eco-friendly roadside noise barrier (RNB) 1:1 scale model was built, and noise levels measured at various points close to it. Significant sound absorption benefits were detected, not only in the shaded area behind the barrier, but also in the unprotected area immediately above the barrier. Furthermore, the economic feasibility of both the construction and recycling processes has been calculated.
Loss of acoustic habitat due to anthropogenic noise is a key environmental stressor for vocal amphibian species, a taxonomic group that is experiencing global population declines. The Pacific chorus frog (Pseudacris regilla) is the most common vocal species of the Pacific Northwest and can occupy human‐dominated habitat types, including agricultural and urban wetlands. This species is exposed to anthropogenic noise, which can interfere with vocalizations during the breeding season. We hypothesized that Pacific chorus frogs would alter the spatial and temporal structure of their breeding vocalizations in response to road noise, a widespread anthropogenic stressor. We compared Pacific chorus frog call structure and ambient road noise levels along a gradient of road noise exposures in the Willamette Valley, Oregon, USA. We used both passive acoustic monitoring and directional recordings to determine source level (i.e., amplitude or volume), dominant frequency (i.e., pitch), call duration, and call rate of individual frogs and to quantify ambient road noise levels. Pacific chorus frogs were unable to change their vocalizations to compensate for road noise. A model of the active space and time (“spatiotemporal communication”) over which a Pacific chorus frog vocalization could be heard revealed that in high‐noise habitats, spatiotemporal communication was drastically reduced for an individual. This may have implications for the reproductive success of this species, which relies on specific call repertoires to portray relative fitness and attract mates. Using the acoustic call parameters defined by this study (frequency, source level, call rate, and call duration), we developed a simplified model of acoustic communication space–time for this species. This model can be used in combination with models that determine the insertion loss for various acoustic barriers to define the impact of anthropogenic noise on the radius of communication in threatened species. Additionally, this model can be applied to other vocal taxonomic groups provided the necessary acoustic parameters are determined, including the frequency parameters and perception thresholds. Reduction in acoustic habitat by anthropogenic noise may emerge as a compounding environmental stressor for an already sensitive taxonomic group.
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.
Classical, vertically erected highway noise walls suffer from a strongly reduced shielding efficiency in case of downwind sound propagation. The driving force for this effect is the presence of strong gradients in the horizontal component of the wind speed. Earth berms, on the other hand, are aerodynamically much smoother. A numerical comparison is made to compare noise walls and berms with a previously validated CFD-FDTD-PE model under downwind conditions. Predictions show that in absence of wind, there is a slight preference for a noise wall if placed at the position of the foot of the berm. Under downwind conditions, noise wall shielding is strongly reduced, while non-steep berms are only affected to a limited degree. When looking at long-term equivalent noise levels, so including periods with wind, shallow berms are therefore preferred upon vertical noise walls.
Transport networks can have significant adverse impacts on biodiversity as well as being a source of pollution for human communities. In addition these networks are also vulnerable to the uncertain impacts of climate change. However, if managed appropriately, transport soft estate has the potential to mitigate these impacts and actually deliver ecological benefits and ecosystem services, as well as making the network more resilient to climate change. This review investigates two research questions considering: i) how transport soft estate has been used to deliver biodiversity gain, ecological connectivity, and ecosystem services; and ii) how green infrastructure has been used to make the transport network more resilient towards climate change. The results suggest that transport soft estate can deliver biodiversity gains and ecological connectivity, but this is very species and context dependent, with success depending on the management regime. Ecosystem service delivery is very promising with soft estate already delivering a variety of services and with the potential to deliver considerably more. The role of green infrastructure in climate change resilience is well developed in other contexts and findings could be transposed to transport networks but more work is required to assess the applicability. Further research could investigate the extent to which transport networks are transitioning from grey engineered to green infrastructure solutions and what hurdles hinder this process.
Following the publication of the UK Government’s Natural Environment White Paper (NEWP) in 2011, a project was initiated with the aim of maximising the ecological connectivity, ecosystem services provision and infrastructure resilience of the UK’s transport soft estate. This project (NEWP 32) was led by Natural England in partnership with the Highways Agency and Network Rail. The project has looked for the first time at how the management of soft estate can be better integrated and linked to adjacent land management to deliver wider benefits, not limited to the Network Rail and Highways Agency estate, with better connection to the wider landscape. The aims of the project were to carry out a literature review in relation to the role of the transport soft estate for biodiversity, ecological connectivity, ecosystems services provision and infrastructure resilience, and then to apply the findings to the transport network at two pilot Nature Improvement Area (NIA) locations: at Humberhead Levels and Morecambe Bay.
The procedure of sound propagation calculation employing the linearized Euler (LE) model has been known to be complex because the procedure requires a chaining of two distinct simulations, namely a fluid dynamics simulation (CFD) in order to solve the background flow field, and a succeeding sound propagation simulation using the LE model over the flow field. The complexity is considered one of the main reasons why the most of the applications of the model remain in investigations assuming highly abstract geometries. In the study, a streamlined workflow is established for LE simulations over a complex urban terrain with its reconstruction utilizing digital geographic models which provide building outline maps and digital surface elevation information. Focus is given to automatic geometry reconstruction and mesh generations of realistic urban terrain. Subsequent processes of CFD and LE simulations are validated through comparisons with published results of wind-tunnel tests and with theoretical solutions. The workflow is deployed to an actual urban terrain of Nagaoka, Japan. The present technique generates a good reconstruction of urban geometry and subsequent split-hexahedral unstructured grid for CFD software and uniform structured mesh for finite-difference LE simulation. The numerical experiments show differences of up to 5 dB between sound pressure levels obtained by the present reconstruction technique and those by a flat-roof geometry. Also, the wind effects are mostly representable in terms of the source-observation point distance in spite of the complex urban configuration. Subtle wind effects of less than 0.5 dB are observed in crosswind condition as well.
The positive effect of a row of trees to improve downwind shielding in the acoustic shadow zone behind a noise wall has been shown before by means of a wind tunnel experiment, a field study and by numerical simulations. This research focused at a rather short distance in downwind direction, where important recovery of the shielding lost by screen-induced wind refraction was observed. However, opposite effects are possible at longer distance. This can be explained by shifts in the zones with strong (positive) gradients in the horizontal component of the wind speed. Leaving a gap between the barrier top and canopy bottom helps reducing these negative effects at longer distance, and results in a generally optimized performance downwind. Trees behind noise walls at either side of the source lead to a full canceling of wind effects at short distance, but to strong negative effects at longer distances downwind. Trees as windbreaks seem to be especially useful near single, vertically erected noise walls. Near steep berms, no net effect of trees is predicted. The design rules presented in this paper are derived based on numerical calculations with a previously validated CFD-FDTD-PE model.
This study mainly aims to explore whether and how urban morphology influences the residential areas' capabilities of attenuating spatial traffic noise level and enlarging quiet area. A set of quantitative urban morphological parameters that are commonly used or accessible in urban design and planning are selected. Noise mapping technique has been employed and a Matlab program has been developed to calculate the spatial sound level indices. The results show that the spatial noise level attenuation mainly happens on noisy facades and noisy open areas, and the attenuation is more sensitive in open areas than on façade; the site with quieter open areas at L 50 or L 60 is prone to have a bigger size of 'Quiet Area'; Building Plan Area Fraction has significant influences on the spatial sound level attenuation on façades for indoor sound environment by traffic noise, and Complete Aspect Ratio and Building Frontal Area Index play important roles on the spatial sound level attenuation in outdoor open areas; Distance of First-row Building to Road and Building Frontal Area Index are the two important parameters for outdoor noisy open area reduction.
Health impacts of environmental noise are a growing concern among both the general public and policy-makers in Europe. This document was prepared by experts in working groups convened by the WHO Regional Office for Europe to provide technical support to policy-makers and their advisers in the quantitative risk assessment of environmental noise, using evidence and data available in Europe. The chapters in this document contain the summary of synthesized reviews of evidence on the relationship between environmental noise and specific health effects, including cardiovascular disease, cognitive impairment, sleep disturbance and tinnitus. A chapter on annoyance is also included. For each outcome, the environmental burden of disease methodology, based on exposure–response relationship, exposure distribution, background prevalence of disease and disability weights of the outcome, is applied to calculate the burden of disease in terms of disability-adjusted life-years. With conservative assumptions applied to the calculation methods, it is estimated that DALYs lost from environmental noise are 61 000 years for ischaemic heart disease, 45 000 years for cognitive impairment of children, 903 000 years for sleep disturbance, 22 000 years for tinnitus and 587 000 years for annoyance in the European Union member states and other western European countries. These results indicate that at least one million healthy life years are lost every year from traffic-related noise in the western part of Europe. Sleep disturbance and annoyance, mostly related to road traffic noise, comprise the main burden of environmental noise. Owing to a lack of exposure data in south-east Europe and the Newly Independent States, it was not possible to estimate the disease burden in the whole of the WHO European Region. The procedure of estimating burdens related to environmental noise exposure presented in this document can be used by international, national and local authorities as long as the assumptions, limitations and uncertainties reported in this document are carefully taken into account.
A two-dimensional (2-D) boundary element method is used to compute the efficiency of noise barriers in attenuating traffic noise. Different types of source are considered. Point sources and incoherent line sources can be introduced as results of a post-treatment of the 2-D pressure field. The insertion loss of barriers is significantly reduced in the case of more realistic incoherent line sources, as compared to that of coherent line sources. However, the relative efficiency of tops added to a straight barrier is higher.
A Green’s function method is used to derive a fast, general algorithm for one‐way wave propagation. The algorithm is applied to outdoor sound propagation. The general method is not limited to atmospheric sound propagation, however, and can be applied to other problems, such as sound propagation in the ocean and electromagnetic wave propagation. The new algorithm, called ‘‘GF‐PE’’ (Green’s function method for the parabolic equation), reduces to the well‐known Fourier split‐step algorithm for the parabolic equation (PE) when no boundary conditions are imposed (e.g., at a ground surface). With the GF‐PE, range steps many wavelengths long are possible, while with a PE algorithm based on a finite‐difference range step, such as the Crank–Nicolson method, the range steps are typically limited to a fraction of a wavelength. Because of its longer range step, the new algorithm is 40–450 times faster than PE algorithms that use the Crank–Nicolson method. For outdoor sound propagation over a locally reacting ground surface, the computed GF‐PE field is the sum of three terms: a direct wave, a specularly reflected wave, and a surface wave. With the new method, the air–ground impedance condition is treated exactly and results in an analytic expression for the surface wave contribution. Numerical results from the GF‐PE model are presented and compared to exact calculations, fast‐field program (FFP) calculations, and PE results computed with the Crank–Nicolson method. The GF‐PE algorithm is shown to be accurate and approximately two orders of magnitude faster than a PE based on the Crank–Nicolson method. Hence, the new algorithm opens the door to some useful new computational capabilities such as real‐time predictions on desktop computers, fast pulse calculations, and practical three‐dimensional calculations.
A numerical method is presented for calculating the sound pressure around a noise barrier of constant but arbitrary cross-section. To obtain the exact solution of this problem, the Helmholtz equation must be solved in the three-dimensional domain outside the barrier. It is shown in this article how to calculate this 3-D sound pressure from solutions of simpler problems defined on the two-dimensional domain outside a cross-section of the barrier. The numerical solution of a large three-dimensional problem is thus avoided and the efficiency of the calculation is considerably improved especially when a whole frequency spectrum is needed. By using the boundary element method to calculate the numerical solutions in the two-dimensional domains, examples are given of determinations of sound pressure fields created by a point source and by an incoherent line source. In this way the efficiency of barriers of different cross-sections can be compared by using the real sound pressure around them. From the frequency spectrum at a point, one can then calculate by Fourier transform the temporal variations of the sound pressure created by a noise source moving in a direction parallel to the barrier.
The effect of a row of trees (in leaf) behind a noise barrier in wind is investigated. An experiment was set up along a highway. Measurements at a location with and without a row of trees behind a noise barrier were compared. This continuously monitoring lasted from the middle of the summer till the middle of fall. It is shown that for downwind sound propagation for an orthogonal incident wind, the efficiency of the noise barrier with trees becomes increasingly better compared to the noise barrier without trees, with increasing wind speed. The improvement by the trees is only slightly affected if the wind direction is not perfectly orthogonal to the barrier. Upwind sound propagation is affected only to a small degree by placing trees. Diffraction on the canopy of trees does not result in an increased total A-weighted sound pressure level due to the typical low-frequency spectrum of traffic noise. The contribution of wind-induced vegetation noise to the recorded noise levels can be neglected for highways with common dense traffic.
The efficiency of noise barriers in downwind direction is strongly reduced by refraction of sound. This effect has been analysed by many authors both in calculations and in experiments. The question arises whether it is possible to influence the wind-factor and to what extent the performance of the barrier could eventually be increased. This paper reports on a wind tunnel experiment set up to try to answer this question. The experiment focuses on the insertion loss close to the barrier (up to a distance of 10 times the barrier height). A model at scale 1/20 is constructed. Both single and double noise barrier (i.e. a noise barrier on either side of the source) configurations are tested, in combination with windscreens. Scale models of vegetative screens are used to modify wind profiles close to the, noise barrier. The positive effect on barrier performance is of the order of a few dB. Although this effect may seem small at first sight, it can be obtained at virtually no additional cost and therefore is of practical interest.
The screen-induced refraction of sound by wind results in a reduced noise shielding for downwind receivers. Placing a row of trees behind a highway noise barrier modifies the wind field, and this was proven to be an important curing measure in previous studies. In this paper, the wind field modification by the canopy of trees near noise barriers is numerically predicted by using common quantitative tree properties. A realistic range of pressure resistance coefficients are modeled, for two wind speed profiles. As canopy shape influences vertical gradients in the horizontal component of the wind velocity, three typical shapes are simulated. A triangular crown shape, where the pressure resistance coefficient is at maximum at the bottom of the canopy and decreases linearly toward the top, is the most interesting configuration. A canopy with uniform aerodynamic properties with height behaves similarly at low wind speeds. The third crown shape that was modeled is the ellipse form, which has a worse performance than the first two types, but still gives a significant improvement compared to barriers without trees. With increasing wind speed, the optimum pressure resistance coefficient increases. Coniferous trees are more suited than deciduous trees to increase the downwind noise barrier efficiency.
The effect of a row of trees (in leaf) behind a noise barrier in wind is investigated. An experiment was set up along a highway. Measurements at a location with and without a row of trees behind a noise barrier were compared. This continuously monitoring lasted from the middle of the summer till the middle of fall. It is shown that for downwind sound propagation for an orthogonal incident wind, the efficiency of the noise barrier with trees becomes increasingly better compared to the noise barrier without trees, with increasing wind speed. The improvement by the trees is only slightly affected if the wind direction is not perfectly orthogonal to the barrier. Upwind sound propagation is affected only to a small degree by placing trees. Diffraction on the canopy of trees does not result in an increased total A-weighted sound pressure level due to the typical low-frequency spectrum of traffic noise. The contribution of wind-induced vegetation noise to the recorded noise levels can be neglected for highways with common dense traffic.
An Eulerian model for sound propagation in an inhomogeneous moving medium is described. The model is based on numerical solution of the linearized Euler equations of fluid dynamics. As the model is formulated in the time domain, common acoustic boundary conditions in terms of a complex acoustic impedance cannot be used. Consequently, the model cannot be used directly for sound propagation over a finite-impedance ground surface. This problem is solved by including the ground medium in the computational system. The ground is modeled as a porous medium with a rigid frame. Numerical examples show that results of the Eulerian model are in excellent agreement with solutions of the Helmholtz equation in the frequency domain.
An efficient hybrid model is presented for sound propagation in situations with several reflecting obstacles near the source. A Finite-Difference Time-Domain (FDTD) model is used in the complex source region, while a Parabolic Equation (PE) model is used for propagation to a distant receiver. The models are coupled by transformation of FDTD results at the boundary of the source region from the time domain to the frequency domain. The FDTD-PE model takes into account multiple reflections of sound waves in the source region, and interaction of sound waves with complex wind fields near the obstacles. It is shown that the FDTD-PE model is accurate, and requires considerably smaller computer times and memory than FDTD does.
Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more than two adjustable parameters. These models and hard-backed-layer versions are considered further through numerical fitting of 42 short range level difference spectra measured over various ground surfaces. For all but eight sites, slit-pore, phenomenological and variable porosity models yield lower fitting errors than those given by the widely used one-parameter semi-empirical model. Data for 12 of 26 grassland sites and for three beech wood sites are fitted better by hard-backed-layer models. Parameter values obtained by fitting slit-pore and phenomenological models to data for relatively low flow resistivity grounds, such as forest floors, porous asphalt, and gravel, are consistent with values that have been obtained non-acoustically. Three impedance models yield reasonable fits to a narrow band excess attenuation spectrum measured at short range over railway ballast but, if extended reaction is taken into account, the hard-backed-layer version of the slit-pore model gives the most reasonable parameter values.
The public, increasingly well-informed about the problem of excessive noise, is taking actions for the development of new transport infrastructure projects and improvement of existing infrastructure. In addition, many countries have implemented mandatory Environmental Impact Assessment procedures. As a result, the construction of sound barriers has become a common measure, which can be used by an agency to mitigate potentially significant noise impacts. A sound barrier, eventually, will become part of the surrounding landscape and could be a cause of impact for ecosystems, the road users and those who live alongside the road. Basically, this article discusses these potential effects in the context of environmental assessment procedures. In addition, results of a pilot survey conducted at a residential area affected by the construction of a barrier are presented. Although most residents felt that sleeping conditions improved after the barrier was built, most important negative reactions are the loss of sunlight and visual impact.
A scale-model facility was developed to test the insertion loss (IL) of highway noise barriers. Three model materials were utilized to simulate packed-earth berms and ground (expanded polystyrene), vertical walls (dense polystyrene), and roadways (varnished particleboard). Thirty-eight noise-barrier configurations were tested and used to compare how IL varied with changes to the barrier profile for walls, berms, and combinations of walls and berms for receivers at a representative, highway-adjacent location. The atmospheric conditions were assumed to be homogeneous and nonrefracting. Changes of barrier surface impedance were also assessed. A highway line source was simulated by positioning both an air-jet point source and a receiver microphone at a series of equally spaced points, in order to form an array of source-receiver measurement pairs making differing angles of propagation to the noise-barrier crest line. The IL measurement results are presented in unweighted third-octave bands. In addition, total A-weighted insertion losses (ILA) were obtained by applying an A-weighted, traffic-noise spectrum. When a berm was modeled with surface impedance closely matching that of packed earth, it was found that walls outperformed berms by 1 to 2 dBA. When the surface impedance of a berm was modeled to be acoustically soft, the ILA increased sufficiently to favor berms by about 2 dBA. The result for an acoustically soft berm does not support the long-standing practice of assuming that earth berms outperform walls by 3 dBA, but is consistent with the performance predicted by newer prediction algorithms. When the slopes of berms were made shallower, the IL generally decreased for a berm alone, but generally increased in cases with a wall atop the berm.
Finite-difference, time-domain (FDTD) calculations are typically performed with partial differential equations that are first order in time. Equation sets appropriate for FDTD calculations in a moving inhomogeneous medium (with an emphasis on the atmosphere) are derived and discussed in this paper. Two candidate equation sets, both derived from linearized equations of fluid dynamics, are proposed. The first, which contains three coupled equations for the sound pressure, vector acoustic velocity, and acoustic density, is obtained without any approximations. The second, which contains two coupled equations for the sound pressure and vector acoustic velocity, is derived by ignoring terms proportional to the divergence of the medium velocity and the gradient of the ambient pressure. It is shown that the second set has the same or a wider range of applicability than equations for the sound pressure that have been previously used for analytical and numerical studies of sound propagation in a moving atmosphere. Practical FDTD implementation of the second set of equations is discussed. Results show good agreement with theoretical predictions of the sound pressure due to a point monochromatic source in a uniform, high Mach number flow and with Fast Field Program calculations of sound propagation in a stratified moving atmosphere.
Experimental measurements were conducted around a right-angle wall to investigate the effect of this obstacle on sound propagation outdoors. Using small explosions as the source of the acoustic waves allowed reflected and diffracted arrivals to be discerned and investigated in detail. The measurements confirm that diffraction acts as a low-pass filter on acoustic waveforms in agreement with simple diffraction theory, reducing the peak pressure and broadening the waveform shape received by a sensor in the shadow zone. In addition, sensors mounted directly on the wall registered pressure doubling for nongrazing angles of incidence in line-of-sight conditions. A fast two-dimensional finite difference time domain (FDTD) model was developed and provided additional insight into the propagation around the wall. Calculated waveforms show good agreement with the measured waveforms.
A scale model study is presented of the performance of thin, perfectly reflecting semi-infinite barriers in the presence of both asphalt and grass-covered surfaces. The barrier insertion loss is shown to be strongly dependent on the type of ground on either side of the barrier. Observed behavior is explained by a study of the interference phenomena occurring in both the barrier's presence and its absence.
Full-scale tests of the acoustical performance are reported on a sound-interference-type barrier profile which has been added to an existing noise barrier used for screening traffic noise. The device was modelled mathematically using the boundary element method approach and comparisons are made between predicted and measured insertion losses. It is concluded that when the additional height of the barrier is taken into account the device provides an estimated gain in average screening performance of 1.9 dB(A) of which 0.7 dB(A) is considered to be due to an interference effect. The remainder is due to the diffraction occurring at the two edges of the device.
A review is presented on the results of previous research, using experimental modelling and field measurement of the insertion loss produced by T-, Y- and arrow-profile noise barriers. A numerical model is discussed which enables the wave field in the region of a barrier with a complex profile and surface cover to be determined. An integral equation formulation of the problem is solved using the boundary element approach. Spectra of insertion loss for T-, Y- and arrow-profile barriers calculated using the model are discussed. Results for the mean insertion loss over a range of receiver positions for a broad-band source are also presented. It is concluded that for barriers with reflecting surfaces the changes in insertion loss for different profiles can be described using the concept of path difference. The introduction of absorbing upper surfaces produces a significant increase in insertion loss. In most conditions the Y- and arrow-profiles perform less efficiently than the T-profile. The marked increase in barrier efficiency when a very thin narrow cap is added to a vertical wall which has been reported by other workers was not observed.
Point source propagation over a screen located on a finite impedance surface representative of grass-covered ground is investigated under upwind and downwind conditions. The theoretical part of the investigation involves extended use of parabolic equation methods (PE) allowing for the changes in the vertical wind speed profile when the wind field passes the screen. The influence of turbulence is also implemented. The experimental part of the investigation relies on a scale model technique based upon a 1:25 scaling ratio and a triggered spark source. The main results relate to the size of the insertion loss of a screen under windy conditions and to the acoustic importance of the redirection of the flow before and after the screen. (C) 1998 Acoustical Society of America. [S0001-4966(98)06511-4].
Modeling experiments are reported which have investigated the frequency dependence of barrier insertion loss for various noise barrier designs. The effect of ground surfaces has been studied, treating both grass-covered ground and asphalt. Results show that interference effects are an important feature of observed behavior. Use is made of this knowledge in the design and testing of new barrier designs, which deliberately introduce a beneficial destructive interference phenomenon to increase insertion losses over well-defined ranges of frequency.
In recent years, various noise barriers have been constructed in Denmark in connection with new dwellings or new roads. Noise barriers are often visually dominant constructions, and they can be an unfamiliar element in the surroundings. In the process of design and planning, it is important to adapt new noise barriers to the surrounding city or landscape, as well as to the actual road. This paper is based on the description of about 40 examples from Denmark, Germany, The Netherlands and France. Great importance is laid on the use of materials, colours and design in the relation to the surroundings. The paper goes through different strategies. One strategy is to use extensive vegetation, so that the noise barrier cannot be seen, especially in the landscape. Another is to make the noise barrier underline the shape and lines of the city and landscape. Some general guidelines for the design of noise barriers are developed.
The growth in the use of noise barriers across Europe, the USA, Australia and the Far East reflects the growing concern of the general public about noise pollution caused by major infrastructure projects, especially roads and railways. This book, which is extensively illustrated with photographs of types of noise barriers has chapters on: defining the need for barriers; the acoustic performance of barriers; barrier morphology and design; types of barriers and barrier materials; engineering safety, environmental and cost considerations. In Appendix 1, details of manufacturers, installers and suppliers are given (for the UK).
Downwind sound propagation over a noise screen is investigated by numerical computations and scale model experiments in a wind tunnel. For the computations, the parabolic equation method is used, with a range-dependent sound-speed profile based on wind-speed profiles measured in the wind tunnel and wind-speed profiles computed with computational fluid dynamics (CFD). It is found that large screen-induced wind-speed gradients in the region behind the screen are responsible for a considerable reduction of the performance of the screen, for receivers near the boundary of the shadow region behind the screen. The screen-induced wind-speed gradients cause a considerable reduction of the size of the shadow region. If the screen-induced wind-speed gradients are taken into account, computed sound-pressure levels near the shadow boundary are in reasonable agreement with levels measured in the wind tunnel. In contrast, computed levels are considerably lower, up to 10 dB, if the screen-induced wind-speed gradients are ignored. This implies that the performance of a screen can be considerably improved if the screen-induced wind-speed gradients can be suppressed, e.g., by the use of "vented" screens. (C) 1999 Acoustical Society of America. [S0001-4966(99)02504-7].
The numerical implementation of the Green's function parabolic equation GFPE method for atmospheric sound propagation is discussed. Four types of numerical errors are distinguished: i errors in the forward Fourier transform; ii errors in the inverse Fourier transform; iii errors in the refraction factor; and iv errors caused by the split-step approximation. The sizes of the errors depend on the choice of the numerical parameters, in particular the range step and the vertical grid spacing. It is shown that this dependence is related to the stationary phase point of the inverse Fourier integral. The errors of type i can be reduced by increasing the range step and/or decreasing the vertical grid spacing, but can be reduced much more efficiently by using an improved approximation for the forward Fourier integral. The errors of type ii can be reduced by using a numerical filter in the inverse Fourier integral. The errors of type iii can be reduced slightly by using an improved refraction factor. The errors of type iv can be reduced only by reducing the range step. The reduction of the four types of errors is illustrated for realistic test cases, by comparison with analytic solutions and results of the Crank–Nicholson PE CNPE method. Further, optimized values are presented for the parameters that determine the computational speed of the GFPE method. The computational speed difference between GFPE and CNPE is discussed in terms of numbers of floating point operations required by both methods.
The sound field due to a point source behind a barrier on ground of finite impedance has been obtained from five theories that differ mainly in their theoretical approach to diffraction and the model for ground impedance. These predicted values have been compared with results measured outdoors using plywood barriers on different combinations of hard and soft ground. Each of these theories allows for interference due to differences between several paths of propagation. One of these theories that agrees well with measurements, has been extended to calculate the sound spectrum level behind a barrier due to an incoherent line source, and further, to calculate the overall or A-weighted sound level for a known source spectrum. Results indicate that there is a significant effect, due to the presence of the ground, that is much greater than that due to absorptive properties of the barrier. Results also predict sound level reductions that differ from predictions using well-known barrier theories.
The paper describes an investigation about the acoustic performance of noise barriers with quadratic residue diffuser (QRD) tops, and with T-, Arrow-, Cylindrical and Y-shape profiles. A 2D boundary element method (BEM) is used to calculate the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface of almost all barrier models presented here is found to improve the efficiency of barriers compare with using absorptive coverage at the examined receiver positions. T-shape and Arrow-shape barriers are also found to provide better performance than other shapes of barriers. The best shape of barriers for utilising QRD among the tested models is the T-shape profile barrier. It is found that reducing the design frequency of QRD shifts the performance improvement towards lower frequency, and therefore the most efficient model for traffic noise is a barrier covered with a QRD tuned to around 400 Hz.
Barrier experiments were conducted in a low speed wind tunnel in which
the flow simulates the mean and fluctuating components of the turbulent
velocity of the atmospheric boundary layer over uniform terrain. The
tests consisted of 1:32 scale model experiments of sound propagating
over grassland, both with and without an acoustic barrier, and also with
and without the presence of turbulent winds. Results show two effects of
the wind on the performance of barriers: (1) the barrier attenuation is
increased for upwind propagation and decreased for downwind propagation,
and (2) the fluctuations in the measured levels of the wind reduction
were of the same order as the mean value.
In the European Harmonoise project aiming at calculating the yearly day/evening/night weighted sound pressure levels from traffic noise the source model is completely separated from the propagation model. This paper presents the source model for road vehicles and discusses some aspects of it taking into account some new investigations carried out in the Nordic countries. The sound power levels of tyre/road noise and propulsion noise are given as equations as a function of frequency, speed and vehicle category. There are 5 different main vehicle categories each of which is subdivided into several sub categories. The sound power level is then distributed between point sources on different heights, each having a given vertical and horizontal directivity. These data refer to a reference condition defined by a constant speed, a specified road surface and a specified temperature. For conditions different from the reference conditions, corrections are given for air temperature, road surface, acceleration/deceleration and road surface wetness. In addition further corrections are possible, such as regional corrections to take into account systematic deviations from the conditions on which the reference equations are based. It is shown that the Harmonoise source model works quite well assuming that some regional corrections are taken into account.
This paper illustrates the use of a numerical time-domain simulation based on the finite-difference time-domain (FDTD) approximation for studying low- and middle-frequency room acoustic problems. As a direct time-domain simulation, suitable for large modeling regions, the technique seems a good ''brute force'' approach for solving room acoustic problems. Some attention is paid in this paper to a few of the key problems involved in applying FDTD: frequency-dependent boundary conditions, non-Cartesian grids, and numerical error. Possible applications are illustrated with an example. An interesting approach lies in using the FDTD simulation to adapt a digital filter to represent the acoustical transfer function from source to observer, as accurately as possible. The approximate digital filter can be used for auralization experiments. (C) 1995 Acoustical Society of America.
The efficiency of noise barriers in downwind direction is strongly reduced by refraction of sound. This effect has been analysed by many authors both in calculations and in experiments. The question arises whether it is possible to influence the wind-factor and to what extent the performance of the barrier could eventually be increased. This paper reports on a wind tunnel experiment set up to try to answer this question. The experiment focuses on the insertion loss close to the barrier (up to a distance of 10 times the barrier height). A model at scale 1/20 is constructed. Both single and double noise barrier (i.e. a noise barrier on either side of the source) configurations are tested, in combination with windscreens. Scale models of vegetative screens are used to modify wind profiles close to the, noise barrier. The positive effect on barrier performance is of the order of a few dB. Although this effect may seem small at first sight, it can be obtained at virtually no additional cost and therefore is of practical interest.
Simulating sound propagation outdoors in time-domain taking into account the effect of wind by means of steady-state Computational Fluid Dynamics (CFD) has recently shown to be very useful. In this paper, the important effect of wind on noise barrier performance and the effect of rows of trees to improve wind profiles around noise barriers are modelled. A finite-difference time-domain simulation model is adapted for sound propagation outdoors in a complex, non-uniform background flow. The simulation of a typical traffic noise situation, where at either side of a line source a noise barrier is present, needs appropriate, non-reflecting boundary conditions like Perfectly Matched Layers (PML) to limit the simulation domain. The PML method is extended for sound propagation in background flow. The numerical model is validated based on two wind tunnel experiments at scale. These show that the model can be used successfully to simulate both the screen-induced refraction of sound and the effect of windscreens to improve downwind noise barrier performance. The influence of parameters involved like the porosity of the canopy of the trees, wind speed and distance between source and noise barrier were studied. Global effects of different configurations of windscreen for typical traffic noise are evaluated in an area of interest behind the downwind noise barrier, exceeding the study region in the wind tunnel experiments.
A flow model in combination with a statistical–dynamical turbulence generator and a linearised Euler time-domain model for sound waves were used to simulate the effect of screen-induced turbulence on the noise level in the acoustical shadow of a screen in wind. Instead of simulating a great number of different frozen turbulence realisations, the concept of transient turbulence was successfully tested and applied. This concept is adequate to the time-domain model and reduces the computational demands. Several two-dimensional simulations allowed to isolate the individual effects of wind and screen on the propagation of 500 Hz sound waves over a 4-m high noise barrier. At a distance of 250 m from the source (240 m behind the screen) the sheltering effect of the screen and the refraction effect of the wind are in the order of 6 and 4 dB, respectively. The screen-induced turbulence leads to fluctuations in the noise level with a standard deviation of 1.2 dB and a maximum amplitude of 3 dB. However, the time averaged effect turned out to be in the order of merely 0.2 dB. The effect of the screen-induced turbulence on the average noise level behind the screen is therefore negligible.
We assessed how listener's judgments of a set of urban sound environments were affected by co-occurring visual settings. In artificial audiovisual environments, subjects rated eight urban sound environments (recordings) when they were associated with five visual settings (four color slides varying in degree of urbanization and a control condition with no slide), along two sound scales (Unpleasant–Pleasant and Stressful–Relaxing). In general, the more urban the visual setting, the more negative the sound ratings. However, this influence depended on the type of sound. It was marked for recordings which did not include human sounds (particularly strong for bird song and weaker for traffic noise), but was absent for all recordings which included human sounds (footsteps and voices). Results are discussed in terms of the degree of matching between visual and sound information, and the degree of implication of the perceiver with these sound environments.
In computational models of wind engineering problems within the atmospheric surface layer the approach flow should normally be modelled as a homogeneous flow. Velocity and turbulence profiles associated with the k-ϵ turbulence model are proposed which produce homogeneous conditions. These equations are discussed in the light of full-scale measurements at Silsoe using sonic anemometers. It is suggested that the model constants k = 0.42, Cμ = 0.013 and σϵ = 3.22 more closely match the data obtained. It is also shown that the cospectrum for the Reynolds stress exhibits a characteristics frequency which is consistent with the suggested profile equations.
The finite-difference time-domain (FDTD) method to solve the linearised equations of fluid dynamics has shown to be very powerful and useful in outdoor sound propagation. Practical applications are however limited due to the large need for computational resources. The numerical discretisation influences computational efficiency to an important degree. In this paper, some possible ways to discretise temporal derivatives are studied. Two obvious ways of time-discretisation namely staggered-in-time (SIT) and a simple collocated-in-time (CIT) scheme are compared to the prediction-step staggered-in-time (PSIT) scheme. The latter is intended to be used for the calculation of sound propagation in the typical low wind speeds encountered in the outdoor environment at low heights above the earth’s surface. It was shown that the PSIT scheme is more stable than the SIT scheme, so practical calculations are possible. Computational efficiency is increased to an important degree compared to the CIT scheme. The numerical accuracy (more precisely the amplitude error) of the PSIT scheme is an important improvement upon SIT. The CIT scheme on the other hand conserves amplitude better. The amplitude error becomes larger with increasing wind speed because of some simplifications during the numerical discretisation. In low wind speeds, the PSIT algorithm can serve as an interesting compromise between numerical accuracy and the required amount of computing power.
The performances of barriers having different shapes and surface conditions were tested using the boundary element method in a well-controlled environment. The heights and widths of the barriers were standardized and the insertion losses for six receiver positions were averaged and compared. Figures displaying the results allow for straightforward barrier performance estimation. It was shown that absorbing and soft edges significantly improve the efficiency of the barrier, but configuration modifications provide only a slight improvement. The soft T-shaped barrier produces the highest performance. A 3 m high T-shaped barrier provides the same performance as a 10 m high plain barrier. The spectral efficiency was also investigated. The insertion loss spectra for the absorbing and the soft barriers exhibit a similar shape, but the rigid barrier differs from these two.
An existing theory on the propagation of spherical sound waves over ground with a finite acoustic impedance is to a large extent verified by field measurements over different types of ground surfaces. It is then shown that it is reasonable to combine this theory with ordinary diffraction theory to get a solution of the mixed problem with a barrier on the ground. Full-scale measurements have been carried out with a 3 m high wall and the results show good agreement with the predicted values. It is also shown that it is generally of minor importance whether a thin screen is sound absorbing or not.
A parameter study is performed for the case of two-dimensional sound propagation from a (source) city canyon to a nearby, identical (receiver) city canyon. Focus was on sound pressure levels, relative to the free field, in the shielded canyon. An accurate and efficient coupled FDTD-PE model was applied, exploiting symmetry of the source and receiver canyon. With the proposed calculation method, simulations were necessary in only half the sound propagation domain. The shielding in the receiver canyon in case of a coherent line source was compared to the shielding by an incoherent line source, by means of sound propagation calculations in a number of 2D cross-sections through source and receiver. It was found that the shielding is rather insensitive to the width-height ratio of the canyons. The presence of diffusely reflecting façades and balconies lead to an important increase in shielding compared to flat façades. Rigid façades yield significantly lower shielding compared to partly reflecting façades. Effects of a moving atmosphere were modeled in detail. Shielding decreases significantly in case of downwind sound propagation when comparing to sound propagation in a non-moving atmosphere. Refraction is the most important effect in the latter. In case of upwind sound propagation, turbulent scattering plays an important role and the shielding is similar to the one of a non-moving atmosphere for the parameters used in this paper. The combination of effects, as is shown by some examples, is in general not a simple addition of the separate effects.
Outdoor sound propagation is significantly affected by the topography (including ground characteristics) and the state of the atmosphere. The atmosphere on its part is also influenced by the topography. A sound propagation model and a flow model based on a numerical integration of the linearized Euler equations have been developed to take these interactions into account. The output of the flow model enables the calculation of the sound propagation in a three-dimensionally inhomogeneous atmosphere. Rigid, partly reflective, or fully absorptive ground can be considered. The linearized Eulerian (LE) sound propagation model has been validated by means of four different scenarios. Calculations of sound fields above rigid and grass-covered ground including a homogeneous atmosphere deviate from analytic solutions by < or = 1 dB in most parts of the computed domain. Calculations of sound propagation including wind and temperature gradients above rigid ground agree well with measured scale model data. Calculations of sound propagation over a screen including ground of finite impedance show little deviations to measured scale model data which are probably caused by an insufficient representation of the complex ground impedance. Further calculations included the effect of wind on shading by a screen. The results agree well with the measured scale model data.
Questionnaire studies were conducted in a residential area before and after the erection of a 2.25 m high noise barrier of conventional type along a heavily traveled road (19,600 vehicles/24 h). The interval between studies was two years. Houses closest to the barrier received a sound-level reduction from -70.0 to 62.5 dB Lden at the most exposed facade. The sound-level reduction decreased with distance to the road, and was negligible for houses at more than 100 m distance. Up to this distance, the noise barrier reduced residents' noise annoyance outdoors and indoors as well as improved speech communication outdoors. Indoors, speech communication and sleep disturbance were slightly but nonsignificantly improved. Predictions of the number of annoyed persons from published exposure-response curves (in Lden) agreed with the percentage of residents being annoyed when indoors, before and after the barrier. Conversely, the percentage of residents being annoyed when outdoors clearly exceeded the predictions. These results suggest that these exposure-response curves may be used in predicting indoor situations, but they should not be applied in situations where outdoor annoyance is at focus.
Switzerland: International Organisation for Standardisation
- Geneva
Geneva, Switzerland: International Organisation for Standardisation.
Rating environmental noise on the basis of noise maps within the framework of the EU Environmental Noise Directive
- H Miedema
- H Borst
Miedema, H., & Borst, H. (2007). Rating environmental noise on the basis of noise
maps within the framework of the EU Environmental Noise Directive. In Proceedings of 36th international congress and exposition on noise control engineering
(INTERNOISE) Istanbul, Turkey.
Addition to: Reducing screen-induced refraction of noise barriers in wind with vegetative screens Numerical simulation of the effect of trees on downwind noise barrier performance
- Van Renterghem
- T Botteldooren
Van Renterghem, T., & Botteldooren, D. (2003a). Addition to: Reducing screen-induced refraction of noise barriers in wind with vegetative screens. Acta Acustica united with Acustica, 89, 381. Van Renterghem, T., & Botteldooren, D. (2003b). Numerical simulation of the effect of trees on downwind noise barrier performance. Acta Acustica united with Acustica, 89, 764–778.
Tyre/road noise reference book
- U Sandberg
- J Ejsmont
Sandberg, U., & Ejsmont, J. (2002). Tyre/road noise reference book. Kisa, Sweden:
Informex.
Computational fluid dynamics software, version 6.3. Centerra Resource Park
- Fluent
Fluent. (2006). Computational fluid dynamics software, version 6.3. Centerra Resource
Park, Lebanon, NH: Fluent, Incorporated.
Burden of disease from environmental noise-Quantification of healthy life years lost in Europe
- L Fritschi
- L Brown
- R Kim
- D Schwela
- S Kephalopoulos
Fritschi, L., Brown, L., Kim, R., Schwela, D., & Kephalopoulos, S. (2011). Burden of
disease from environmental noise-Quantification of healthy life years lost in Europe,
WHO European Centre for Environment and Health. Bonn Office.