| 1. |
- Ageborg Morsing, Julia, et al.
(author)
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Wind Turbine Noise and Sleep: Pilot Studies on the Influence of Noise Characteristics
- 2018
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In: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1661-7827 .- 1660-4601. ; 15:11
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Journal article (peer-reviewed)abstract
- The number of onshore wind turbines in Europe has greatly increased over recent years, a trend which can be expected to continue. However, the effects of wind turbine noise on long-term health outcomes for residents living near wind farms is largely unknown, although sleep disturbance may be a cause for particular concern. Presented here are two pilot studies with the aim of examining the acoustical properties of wind turbine noise that might be of special relevance regarding effects on sleep. In both pilots, six participants spent five consecutive nights in a sound environment laboratory. During three of the nights, participants were exposed to wind turbine noise with variations in sound pressure level, amplitude modulation strength and frequency, spectral content, turbine rotational frequency and beating behaviour. The impact of noise on sleep was measured using polysomnography and questionnaires. During nights with wind turbine noise there was more frequent awakening, less deep sleep, less continuous N2 sleep and increased subjective disturbance compared to control nights. The findings indicated that amplitude modulation strength, spectral frequency and the presence of strong beats might be of particular importance for adverse sleep effects. The findings will be used in the development of experimental exposures for use in future, larger studies.
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| 2. |
- Alves, Sonia, et al.
(author)
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Urban sound planning - The SONORUS project
- 2016
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In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. ; , s. 2319-2328
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Conference paper (peer-reviewed)abstract
- Sound is still insufficiently considered in most urban planning processes, resulting in unsatisfactory sonic environments that might even present health risks to citizens. No matter how complex and challenging the planning project might be, the creation or preservation of acoustically favorable environments should be part of urban planning. To support this process, the SONORUS project developed a holistic approach for urban sound planning and showed its benefits with practical test cases. The goal of the holistic approach is to facilitate the integration of sonic planning in an earlier stage of the planning process by combining different approaches and by providing new tools and methods, thus enabling urban planners to achieve healthy and supportive sound scenarios.
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| 3. |
- Berghauser Pont, Meta, 1972, et al.
(author)
-
Increasing cities' capacity to manage noise and air quality using urban morphology
- 2019
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In: Book of Abstracts XXVI International Seminar on Urban Form “Cities as Assemblages”. ; , s. 42-42
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Conference paper (other academic/artistic)abstract
- According to the World Health Organization, the top two in disease burden are air pollution and environmental noise. In cities, road traffic is the largest contributor to both noise and air pollution and the corresponding Swedish Environmental objectives are to date estimated to not be reached by 2020. Future reductions concerning both air quality and noise are considered insufficient whereby additional measures are needed. Air quality is linked to urban form such that compact cities were shown to result in increasing concentrations of air pollution. Further, urban form influences the meteorology due to changed surface roughness on the larger scale (urban scale), and even more in a local- and microscale at ground level in street canyons. This will affect wind patterns influencing the dispersion possibility of air pollutants. For investigating local effects of urban morphology on noise and air distribution simultaneously, the Spacematrix method has been shown to be useful, as described in Berghauser Pont and Haupt (2010). Building types can be composed of a combination of density variables enabling to quantify a type and manipulate each variable separately. The aim of this paper is to identify critical spatial parameters influencing noise and air pollution and translate them into measures of spatial form including size of the urban block, and distribution, positioning and height of the buildings within that block.
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| 4. |
- Berghauser Pont, Meta, 1972, et al.
(author)
-
Using urban form to increase the capacity of cities to manage noise and air quality
- 2023
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In: Urban Morphology. - 1027-4278. ; 27:1, s. 51-70
-
Journal article (peer-reviewed)abstract
- The top two environmental factors adversely affecting human health in Europe are air and noise pollution, with road traffic being the largest source. Urban density plays an important role in reducing car traffic. However, the benefits of reduced emissions per capita can still mean higher emissions locally, because of the number of people in the area. Therefore, this paper investigates how morphological parameters influence the local distribution of noise and air pollution. A parametric approach, based on the Spacematrix method, is used to study the impact of morphological parameters on the distribution of air and noise pollution, controlling for traffic mode, flows and speed. To compare the impact of exposure to noise and air pollution, their respective health burden is calculated using disability-adjusted life years (DALYs). The results, based on 31 models of different forms, show that the degree of openness greatly affects performance with opposite effects for noise and air pollution. Building types with slightly open yards, like open corner blocks, may provide an attractive compromise solution due to their relatively good noise exposure situation at the same time as the dispersion of air pollutants improves. Adding sound absorbing vegetation is an effective measure to mitigate noise, especially for blocks with openings, limiting the propagation of sound into the yard. Further, densification is beneficial for health if the increase in density does not increase traffic volume in the same proportion. Densification by adding towers on a perimeter building block gives the best results for health as it combines a less noisy yard, thanks to the enclosure of the yard with towers, which enhances turbulent mixing of air within the street canyon.
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| 5. |
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| 6. |
- Bergman, Penny, 1982, et al.
(author)
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Perceptual validation of auralized heavy-duty vehicles
- 2015
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In: Euronoise 2015. ; , s. 769-774
-
Conference paper (peer-reviewed)abstract
- Auralization is a valuable tool when evaluating the effect of traffic noise on people. The present study focuses on the validation of auralization of heavy-duty vehicles with a diesel engine. To capture the characteristics of the diesel engine a granular approach has been used. The granular approach has proven to be successful in a previous validation test examining two microphone positions around a still-standing truck. In the present study a granular approach was used to achieve pass-by noise at an artificial listening position alongside a Volvo truck (experiment 1) and pass-by noise inside an apartment (experiment 2). The aim of experiment 1 was to determine the number of interpolated sets of grains needed, in order to create a perceptually valid auralized signal. The results were used in the auralization of pass-by noise in an apartment in experiment 2. 20 and 15 participants respectively rated original recordings and auralized signals on four different attributes: realism, annoyance, and emotional response measured by valence and arousal. The results of both experiments suggest that auralizations of heavy-duty vehicles are successful and usable. It further indicates that what distinguish the auralized signals from the original recordings is mostly the arousal responses.
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| 7. |
- Dashti, Fatemeh, 1991, et al.
(author)
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Finite Element Modelling of Tunnel Shielding in Vibration Measurements of Ground-Borne Noise
- 2024
-
In: Lecture Notes in Mechanical Engineering. - 2195-4356 .- 2195-4364. ; 14th International Work-shop on Railway Noise, IWRN 2022, s. 723-730
-
Conference paper (peer-reviewed)abstract
- Several factors can affect vibration levels during transmission from a tunnel to the ground surface. This study investigates the effect of a tunnel cavity in bedrock with force excitation at the tunnel floor. The tunnel geometry affects the wave propagation around the tunnel and the directivity pattern of waves propagating to the ground surface. For instance, there is no direct propagation path of ground waves from the excitation in the tunnel floor to positions on the tunnel walls. The waves reaching the walls have been diffracted at the tunnel corners. This tunnel shielding effect is here investigated regarding sensor position and direction and directivity of wave propagation up to 1 kHz using the finite element method. An underground tunnel is modelled in 2D and 3D for a bedrock ground typical for Swedish conditions. The results show that the velocity levels at the tunnel floor are higher than at the tunnel wall. It is also shown that the tunnel shielding effect causes decreased vibration levels at mid-frequencies above the tunnel and significant level fluctuations, especially at higher frequencies. The results from the 3D modeling support the 2D results.
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| 8. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
Dynamic traffic noise assessment tool: A comparative study between a roundabout and a signalised intersection
- 2018
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 130, s. 71-86
-
Journal article (peer-reviewed)abstract
- Considering traffic flow as a steady noise source is common practice when studying traffic alternatives and its impact on the sound environment. However, vehicle dynamics have a strong influence on both transport behaviour and noise emission. One of the most relevant elements of traffic design is the intersection, where replacement of crossing intersections with roundabouts is common. In order to understand the features of these two traffic configurations, microscopic approaches are needed, making it possible to study time-pattern fluctuations relevant for the urban sound environment perception. A model based on individual-vehicle characteristics as function of time is developed and implemented in a real case study at a development stage. The model incorporates state-of-art microscopic traffic simulation software combined with the recent noise emission model, CNOSSOS-EU, applied through an in-house developed dynamic traffic noise tool, including both internal combustion engine and all-electric vehicles at different traffic flows. The tool is described in general terms incorporating the randomisation of source power. The propagation considers a flat-city configuration up to 100 m range. The tool enables study of different statistical indicators, including descriptors of probability density functions, calm periods through the novel indicator Centre of Mass Time (CMT) and noise events. The outcomes are presented through graphs and maps explaining traffic disruptions, acceleration effects, vehicle configurations and flows, source strengths, contribution and difference maps. Among the results, it is shown that, for the signalised crossing, the acceleration of the simulated traffic has a large effect on the source strength. It is however also shown that, for an unbalanced roundabout intersection leading to congestions, it can become noisier than the signalised crossing. It is furthermore shown that, when reducing the traffic flow, the two intersection types behave more similarly; however the roundabout having the best performance for the majority of the studied analysis. Further results are shown, e.g. for removing heavy vehicles, removing also medium heavy vehicles and assuming only all-electric light vehicles, including analysis from using various indicators. A discussion about the presented tool, the current results and ideas for future work concludes the paper. The present paper goes along a series of studies with the overall intention to provide a more solid basis for justifying decisions in traffic planning regarding the outdoor sound environment.
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| 9. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
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Incorporation of the quiet side in noise maps
- 2014
-
In: TECNIACUSTICA 2014. 45st SPANISH CONGRESS ON ACOUSTICS. 8 th IBERIAN CONGRESS ON ACOUSTICS. EUROPEAN SYMPOSIUM ON SMART CITIES AND ENVIRONMENTAL ACOUSTICS. - 2340-7441. - 9788487985256 ; , s. 123-130
-
Conference paper (peer-reviewed)abstract
- Nowadays noise maps are focused on the noise level at the most exposed façade, leading to underestimations on the shielded areas. Previous research showed that quiet areas have positive effects for the inhabitants' quality of life. To solve this problem, an engineering method was developed within the QSIDE project. This method aims to improve noise maps in terms of multiple reflections in an efficient way. Two different terms, attenuation due to the barrier and the canyon will be incorporated. In this paper, the suggested model from QSIDE has been further developed for its inclusion in noise map calculations.
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| 10. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
Is the sound environment relevant for how people use common spaces?
- 2018
-
In: Building Acoustics. - 1351-010X. ; 25:4, s. 307-337
-
Journal article (peer-reviewed)abstract
- Rapid and intrusive spatial adjustments in common spaces are increasingly questioned by the awareness of citizens demanding higher quality standards. This study aims to understand the use of common space by identifying how the sound environment affects the functions of space and the interaction with other environmental and spatial variables. Is there a certain sound environment required or that should be avoided when designing a space for a specific activity? In situ evaluations with regular users were collected in nine common spaces in Gothenburg, Sweden, conducting sound recordings and questionnaires. Site selection responded to the purpose of the analysed places, the noise level (LAeq) of the city road traffic noise map, and the number of activities suggested by the city sociotope maps. The analyses revealed that certain activities could be identified from LAeq values. Discriminant functions with respect to sound levels primarily identified a tranquil/restorative vibrant dimension, where the highest noise levels tend to be at the most vibrant end. Other results showed that a considerable variability of overall and visual quality judgements came from the variability in sites. These quality assessments were highly correlated, allowing both to be analysed as a single attribute. The variability in sound quality was much lower. Notable is the difference between recorded and perceived loudness. In addition, poor sound quality judgement does not seem to correlate with the perception of mechanical sources as the main source of noise.
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| 11. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
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Isolating key features in urban traffic dynamics and noise emission: a study on a signalized intersection and a roundabout
- 2016
-
In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future.
-
Conference paper (peer-reviewed)abstract
- Urban planning and transport network are considered as major urban systems with great impact on the sound environment. Most of the work done in transport management and traffic design to improve the quality of both outdoor and indoor sound environment relies on conventional noise mapping software outcomes. This type of tool is based on macroscopic traffic modelling, considering traffic flow as a steady noise source. A commonly implemented practice intended to reduce noise in urban areas is the transformation of a signalised crossing into a roundabout. However, the individual vehicle behaviour becomes relevant in these decisions, where high time-pattern fluctuations are responsible for changes in the quality of the urban sound environment and of human activity. The present paper studies a set of indicators from isolated key features in these two road traffic configurations and their possible variations (acceleration, heavy vehicles, etc.). A VISSIM microscopic traffic simulation model combined with the CNOSSOS-EU noise emission model is used to test cases based on real situations, now in development stage. The approach presented aims to provide stronger basis in the reasoning behind why different road traffic configurations adopted in the urban planning practice give certain effects in relation to the urban sound environment.
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| 12. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
Let the Children Listen: A First Approximation to the Sound Environment Assessment of Children through a Soundwalk Approach
- 2020
-
In: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1661-7827 .- 1660-4601. ; 17:12, s. 1-18
-
Journal article (peer-reviewed)abstract
- The urban sound environment is one of the layers that characterizes a city, and several methodologies are used for its assessment, including the soundwalk approach. However, this approach has been tested mainly with adults. In the work presented here, the aim is to investigate a soundwalk methodology for children, analyzing the sound environment of five different sites of Gothenburg, Sweden, from children's view-point, giving them the opportunity to take action as an active part of society. Both individual assessment of the sound environment and acoustic data were collected. The findings suggested that among significant results, children tended to rank the sound environment as slightly better when lower levels of background noise were present (LA90). Moreover, traffic dominance ratings appeared as the best predictor among the studied sound sources: when traffic dominated as a sound source, the children rated the sound environment as less good. Additionally, traffic volume appeared as a plausible predictor for sound environment quality judgments, since the higher the traffic volume, the lower the quality of the sound environment. The incorporation of children into urban sound environment research may be able to generate new results in terms of children's understanding of their sound environment. Moreover, sound environment policies can be developed from and for children.
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| 13. |
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| 14. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
SONORUS Urban sound planning project and test sites: an example within the planning stage
- 2016
-
In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future.
-
Conference paper (peer-reviewed)abstract
- SONORUS Urban sound planning project looks towards a proactive planning for improved sonic environments, coupled with the variables influencing the quality of life in cities. The project embraces a holistic urban planning approach, involving acoustics at the planning stage as another variable capable to enrich the built environment. To connect the research carried out with practical implementations, SONORUS incorporates four real case studies with different characteristics and a common demand on the improvement of the sound environment at different stages. This paper focuses mainly on Frihamnen test site (Gothenburg, Sweden), considered a strategic city project with the intention to transform the space into a dense mixed-use area. The paper goes through a general introduction framing the holistic approach in urban sound planning at four test sites. The discussion is centred in the research within Frihamnen and the workshop carried out with SONORUS members and city representatives, with the intention to analyse the acoustic situation and understand the impact of future developments on the sound environment. Finally, the work discusses about the consequences and possibilities that the holistic approach might have in urban sound planning and the entire urban planning process as a driving force to improve the liveability of spaces.
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| 15. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
Soundwalks in Gothenburg
- 2016
-
Reports (other academic/artistic)abstract
- The present report presents the results of a series of soundwalks carried out in the city of Gothenburg as part of the “Framtidsveckan 2015” activities. The study was developed inside the EC project SONORUS Urban Sound Planning in collaboration with the Environmental Office of the city of Gothenburg.The goal is to analyse the sound environment at different locations from the citizens’ point of view through a series of questions while at the same time, sound recordings and acoustical indicator data is obtained. Thereby, thecitizens’ will have the opportunity to contribute to the present and future urban development, including urban sound planning, in the planning agenda. Moreover, the intention is to increase awareness among citizens in terms of noise exposure and sound quality, in addition to make them part of the study of their city. The soundwalks took place in October 2015.
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| 16. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
Traffic dynamics, road design and noise emission: a study case
- 2015
-
In: Euronoise 2015, 10th European Congress on Noise Control Engineering.
-
Conference paper (peer-reviewed)abstract
- Traffic management and traffic design have been issued as the main solutions to reduced problems related to mobility. In relation with noise mapping, traffic simulation is usually based on macroscopic modelling, with e.g. mean speed and flow as output. However, dynamics in terms of acceleration have a strong influence on noise emission. In the current paper, road traffic noise emission is calculated with dynamic traffic as input. A real case, now in planning stage, is used as a setting containing several traffic design alternatives. The resulting total noise emission is calculated for the different traffic and road design solutions by using a microscopic traffic simulation model (VISSIM) combined with a model for noise emission (CNOSSOS-EU). The qualities of the resulting traffic and noise situations are discussed.
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| 17. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
-
Urban space and the sound environment: Transport system, urban morphology, quiet side and space users in the SONORUS project
- 2016
-
In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. ; , s. 2928-2938
-
Conference paper (peer-reviewed)abstract
- Awareness on urban environmental quality is leading the built environment resilience and sustainability vision, highlighting the importance of a multidisciplinary framework on urbanization processes. A main concern is the negative impact of outdoor noise due to road traffic, determined largely by the source strength, i.e. the vehicles. This paper summarizes the work within the optimization of urban areas inside the SONORUS Urban sound planning project. The purpose is to provide urban planning tools focusing on interacting approaches through the traffic planning and buildings as instruments supporting a better urban environment, with noise as the main indicator. First, the prediction modelling for quiet sides based on the Qside model is implemented and tested on cases measured in situ. Second, a microscopic road traffic modelling tool gives useful output for noise level predictions as function of time, opening the possibility to calculate noise indicators and test traffic configurations. Discussion extends towards the study of urban morphology diversification, considered a key strategy to increase liveability of spaces, its interaction with the transport system and the impact on the sound environment. Finally, interest focuses on space users modelling their environment beyond noise control, using the soundwalk as a tool to study urban sound experience.
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| 18. |
- Forssén, Jens, 1968, et al.
(author)
-
A low-height acoustic screen in a setting with an urban road: measured and predicted insertion loss
- 2016
-
In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. - 9783939296119 ; , s. 6435-6443
-
Conference paper (peer-reviewed)abstract
- A low screen was temporarily installed alongside an urban road to test the acoustic performance. Within the on-going project, the screen is an acoustic prototype, whereas later, a screen design will be developed considering also perceived acoustic quality and visual aspects. The current acoustic prototype, built up from concrete modules, was placed beside a small park on the reservation between a two-lane road and a track for walking and cycling. A larger traffic system, of which the two-lane road is a part, determines the daytime equivalent noise level within the urban area. The screen height was about 1.3 m as measured from the level of the road surface and the width of the screen top was 0.3 m. Measurements were carried out both at 20 m distance from the road (within the park) and at 5 m distance from the road (on the cycle track). Insertion loss in maximum level, using controlled light vehicle pass-by at 50 km/h, was measured to 10 dB and 6 dB at 5 and 20 m distance, respectively, at 1.5 m height. The measured results have been compared with those predicted by both a noise mapping software and a boundary element method, showing reasonable agreement.
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| 19. |
- Forssén, Jens, 1968, et al.
(author)
-
A Model of Sound Scattering by Atmospheric Turbulence for Use in Noise Mapping Calculations
- 2014
-
In: Acta Acustica united with Acustica. - : Wissenschaftliche Verlagsgesellschaft mbH. - 1610-1928 .- 1861-9959. ; 100:5, s. 810-815
-
Journal article (peer-reviewed)abstract
- Sound scattering due to atmospheric turbulence limits the noise reduction in shielded areas. An engineering model is presented, aimed to predict the scattered level for general noise mapping purposes including sound propagation between urban canyons. Energy based single scattering for homogeneous and isotropic turbulence following the Kolmogorov model is assumed as a starting point and a saturation based on the von Karman model is used as a first-order multiple scattering approximation. For a single shielding obstacle the scattering model is used to calculate a large dataset as function of the effective height of the shielding obstacle and its distances to source and receiver. A parameterisation of the dataset is used when calculating the influence of single or double canyons, including standardised air attenuation rates as well as facade absorption and Fresnel weighting of the multiple facade reflections. Assuming a single point source, an aver aging over three receiver positions and that each ground reflection causes energy doubling, the final engineering model is formulated as a scattered level for a shielding building without canyon plus a correction term for the effect of a single or a double canyon, assuming a flat rooftop of the shielding building. Input parameters are, in addition to geometry and sound frequency, the strengths of velocity and temperature turbulence.
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| 20. |
- Forssén, Jens, 1968, et al.
(author)
-
A model study of low-frequency noise exposure indoors due to road traffic
- 2023
-
In: Building Acoustics. - 1351-010X .- 2059-8025. ; 30:1, s. 3-24
-
Journal article (peer-reviewed)abstract
- Indoor low-frequency noise levels due to road traffic has been modelled for facade examples consisting of a lightweight steel facade, a concrete facade and two types of windows. Possible audibility of heavy vehicles passing by has been investigated as well as the dependence of the exposure level on driving speed and distance to road. The results show that pass-by events may be audible at low frequencies for cases complying with building standards and noise guideline values exemplified by Swedish regulation. Moreover, the A-weighted levels may be dominated by low frequency noise, and the frequency of occurrence of pass-by traffic noise events may be sufficiently high to create disturbance for typical traffic situations. Furthermore, it is shown that the contribution of pass-by events to the equivalent level indoors may increase when the driving speed is lowered.
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| 21. |
- Forssén, Jens, 1968
(author)
-
A technical note on modelling the effect of source motion on amplitude and Doppler shift using resampling
- 2023
-
Reports (other academic/artistic)abstract
- Modelling of the sound field due to a simple monopole source moving at subsonic speed is investigated. It is shown that both the Doppler shift and the influence of the Doppler factor on the amplitude and the directivity can be modelled by a single resampling process demanding area conservation. This is the main novel contribution of the paper. Here, the Doppler factor is defined as $(1-u_r/c)^{-1}$, where $u_r$ is the component of the moving source velocity in the direction of the receiver and $c$ is the sound speed. The paper may contribute to an increased understanding of the reasons for the Doppler factor in relation to higher order convective factors.
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| 22. |
- Forssén, Jens, 1968
(author)
-
An analytical solution for a low barrier in a turbulent atmosphere
- 2004
-
In: Acta Acustica united with Acustica. - 1610-1928 .- 1861-9959. ; 90:6, s. 1142-1150
-
Journal article (peer-reviewed)abstract
- The work presented here uses a previously developed substitute sources method (SSM) as the starting point for solving the problem with a low barrier in a turbulent atmosphere. The formulation of the SSM involves a double integral and the numerical solution is computationally demanding. The SSM results are here used as reference. As an intermediate step toward an analytical solution, an expression containing a single integral is found. Its implementation is computationally much less demanding and is here called the fast method. The analytical solution involves further approximations and has a smaller range of validity than the fast method, but could nonetheless be useful. Both the fast method and the analytical solution assume a flat geometry, whereby they can be useful as a complement to scattering cross-section based methods. Moreover, two-dimensional (2-D) modelling is done and no ground surface is considered. Agreement between the SSM and the fast method is reasonably good, and additional restraints are formulated for the applicability of the analytical solution.
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| 23. |
- Forssén, Jens, 1968
(author)
-
An analytical solution for a low barrier in a turbulent atmosphere
- 2005
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In: Proc. Forum Acusticum, Budapest, Hungary, 2005..
-
Conference paper (other academic/artistic)abstract
- Buildings and other kinds of sound barriers are commonly used to reduce traffic noise. Atmospheric turbulence causes scattering of sound into the shielded zones created by barriers. The sound level increase is expected to be significant usually for large geometries, and at higher frequencies. For steep geometries, i.e. with a high barrier close to the source or to the receiver, a scattering cross section based model can be used to predict the increase in sound level. Here, another approach is used, which is applicable to flat geometries, i.e. where the barrier is low in comparison to its distance to both the source and the receiver. The work is based on a previously developed substitute sources method (SSM). A two-dimensional modelling is done and no ground surface is considered. To numerically solve the full SSM formulation of the problem is computationally demanding due to a double integral. To reduce the computational cost, an analytical solution is derived. As an intermediate step an expression containing a single integral is found, which enables a numerically fast method. The full SSM formulation is used as reference, and agreement between the SSM and the fast method is reasonably good. The analytical solution involves further approximations and has a smaller range of validity than the fast method. Additional restraints are formulated for the applicability of the analytical solution.
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| 24. |
- Forssén, Jens, 1968
(author)
-
An extended substitute-sources method for a turbulent atmosphere: Calculations for upward refraction
- 2003
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In: Acta Acustica united with Acustica. - 1610-1928 .- 1861-9959. ; 89:2, s. 225-233
-
Journal article (peer-reviewed)abstract
- The substitute-sources method (SSM) was previously implemented for a single noise barrier in a turbulent atmosphere by applying a substitute surface between the barrier and the receiver [1, 2]. Here, the method is extended, aiming to more general applicability to traffic noise propagation in urban environments. In the method, multiple substitute surfaces are used along the propagation path. The atmospheric turbulence causes a transfer of the initially coherent field into a residual, random field along the propagation path. The mean sound level at the receiver position is found from uncorrelated addition of the substitute surfaces' contributions. The calculation of each contribution is based on a mutual coherence function (MCF) for a turbulent atmosphere. The strength of the substitute sources and the Green functions to the received pressure are calculated for a non-turbulent atmosphere, here by using a fast field program (FFP). A special MCF for the residual field is derived. Examples are calculated for a turbulent atmosphere with upward refraction or without refraction. The results are compared with those from a parabolic equation method (PE) for the refractive cases and with an analytical solution otherwise. The results show good agreement, which indicates that the SSM could be useful for predictions of outdoor sound propagation.
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| 25. |
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