Showing papers on "Noise barrier published in 2020"

Exposure assessment to road traffic noise levels and health effects in an arid urban area

Abstract: Road traffic noise exposures have been recognized as serious environmental health concerns, especially in most developing countries with arid climate conditions, rapid increase in vehicle population, and limited traffic management systems The excessive noise exposure level is associated with increase in the incidence of cardiovascular diseases and anxiety, including annoyance This study aimed at determining traffic noise levels in residential areas, including the assessment of its annoyance and health effects based on the people's perception and reportage To do so, field measurement and traffic noise modeling were carried out in six road points to estimate the current noise levels along various roads close to human inhabitants in Muscat Governorate, Sultanate of Oman The detailed measured noise levels in urban residential areas across the selected roads showed that noise levels have exceeded the local and international threshold limits at all locations during the entire day The high sound levels (480-563 dBA) were observed using the US Federal Highway Administration's Traffic Noise Model (TNM, version 25) results, which were in agreement with the observed (563-604 dBA) data To assess health implication to residents through interviews (n = 208), annoyance at home was found to be little (32%), moderate (28%), and high (9%) in comparison with workplace settings of 42%, 43%, and 15%, respectively Nineteen percent of the interviewees had difficulties in sleeping, while 198% experienced stress due to road traffic noise exposures Moreover, a strong association (p < 005) was established between the use and objection of noise barriers The study revealed high noise levels and the prevalence of annoyance and health effects among the exposed population Therefore, immediate action is required to tackle the current noise levels

Geographic Ecological Momentary Assessment (GEMA) of environmental noise annoyance: the influence of activity context and the daily acoustic environment.

Abstract: Noise annoyance is considered to be the most widespread and recognized health effect of environmental noise. Previous research is mostly based on the static study of residential environmental noise, but few studies have focused on the effects of noise exposure in different activity contexts on real-time annoyance. The two deficiency are that they neglect the influence of activity context besides residence and fail to reflect the difference of time-scale effect of noise influence. Using portable noise and air sensors, GPS-equipped mobile phones, questionnaire survey, and geographic ecological momentary assessment (GEMA), this paper measured the environmental noise and real-time noise annoyance of participants at different activity places. Hierarchical logistic regression models were used to examine the effects of environmental noise on people’s real-time annoyance. The paper further considered the influence of the geographic context of the activity places and daily acoustic environment on participants’ real-time annoyance. Further, a nonlinear regression model was constructed using Random Forest to further examine the nonlinear relationship between environmental noise and real-time annoyance. The results showed that: (1) the average cumulative equivalent sound level during was 55 dB (A) when the participants responded to the EMA surveys; (2) Only the temperature of activity places had an influence on momentary annoyance and the higher the temperature, the more likely participants were annoyed; (3) Participants with higher perception of noise pollution in residential communities were more likely to be annoyed. However, participants with higher daily exposure to noise were less likely to feel annoyed; (4) The threshold value of the effect of noise on real-time annoyance was 58 dB (A) to 78 dB (A). These findings can guide the development of urban planning and environmental noise standards and also provide a reference for noise barrier requirements for different activity places.

Effect of cavity flow control on high-speed train pantograph and roof aerodynamic noise

Abstract: The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains. Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph. However, less attention has been paid to the pantograph recess compared with the pantograph. In this paper, the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess, which is represented as a rectangular cavity and numerically investigated at 1/10 scale. Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation, and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction. The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications, and consequently, the noise radiated from the cavity is reduced. Furthermore, effects of the rounded cavity edges on the flow and noise of the pantographs (one raised and one folded) are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges. Different train running directions are also considered. Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph, whereas the flow velocity in the cavity is slightly increased by the rounding. Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph, whereas weaker fluctuations are found on the panhead of the raised pantograph. This study shows that by rounding the cavity edges, a reduction in radiated noise at the side and the top receiver positions can be achieved. Noise reductions in the other directions can also be found.

Aerodynamic Effects as a Maglev Train Passes Through a Noise Barrier

Abstract: The aerodynamic performance of a maglev (magnetic levitation) train (MT) passing through a two-sided noise barrier was simulated by the improved delayed detached eddy simulations. The influence of the presence of noise barrier on both sides on the flow field around the MT and the pressure field in the noise barrier area are analyzed. The effect of changes of the noise barrier height and the centre of track (COT) distance parameter on its flow field were also studied. Numerical simulation results were verified by the moving model test. The results show that the noise barrier increases the pressure in the area around a train. The maximum pressure changes most as the tip of the head of the MT passes through the measuring point. The maximum positive and negative pressure amplitudes of the head wave on the inner wall surface of the noise barrier are increased by 83.5% and 58.4% compared to those the same height position measurement point in open air. On the inner wall of the barrier, the fluctuation of the pressure decreases with the increased height of the probe, which is opposite to the trend on the outer wall. Inside the noise barrier, the wind velocity in the x-direction is greater than that in open air when the tip of the nose and tail of the car passes. But the velocity in the y-direction when the tip of the head and tail cars passes is limited, and two speed peaks appear in the horizontal direction train induced wind. The higher the noise barrier, the higher pressure of the same height measurement point in the noise barrier area. Due to the passage of the train, the top of the noise barrier has a certain vorticity at the position of the head car and the tail car. Changing the height of the noise barrier changes how the vortex structure at the tail of the train develops. Moving the noise barrier further from the COT causes the fluctuations at the pressure measurement point inside the noise barrier to diminish meaning the pressure enhancement effect caused by the height of the noise barrier also diminishes.

Suitability of Active Noise Barriers for Construction Sites

Abstract: Barriers are increasingly used to protect the pedestrian and neighboring buildings from construction noise activities. This study aims to investigate the suitability of applying active noise control on barriers in a construction site to protect the street area and neighboring buildings. Transducers that are simulated in this work are close to the barrier, and their optimal positions are defined in such a way that the control system has the maximum performance at the neighboring areas close to the construction sites. To begin with, the suitable location of the control sources is found when the total squared pressure is minimized at the positions of noise receivers. The suitable location of the error sensors is, then, found when the control sources are fixed at the position of the previous step and the total squared pressure is minimized at the error sensors. The best location for the error sensors is defined when the maximum reduction is achieved in the target area. It is observed that suitable positions for the transducers depend on the location of target areas for noise control, the position of the noise source, and its operating frequency. In this investigation, a unique configuration is proposed for the transducers that achieves a comparable reduction both at the street area and the neighboring buildings, simultaneously. The results show that the active noise barrier with a height of 2.5 m can achieve an extra insertion loss in the street zone, varies from 9.3 to 16.4 dB (in comparison with passive noise barrier) when the distance of the noise source from the barrier changes in the range of 7 to 1 m, respectively. Those values are of the same order for the passive noise attenuation. Furthermore, similar results are achieved when attempting to cancel the shadow zone of a facade 15 m away from the barrier.

On the Control of Low-Frequency Audible Noise from Electrical Substations: A Case Study

Abstract: With the world facing the urgency of energy transition, the development of efficient and quiet electrical infrastructures is of topical importance in the construction of the environment of the future. The problem of noise from power distribution systems is often underestimated, although several works in the literature underline the effect of disturbance on the population, especially concerning the low frequency range. This paper overviews the issue of the low-frequency noise generated by electrical substations, from the experimental characterization of the source to the possible mitigation measures at the source, along the propagation path and at the receiver. Alongside the general presentation, a case study serves as a practical demonstration of the proposed methodological approach. It was found that in the investigated situation the main disturbance comes from the transformer at two low-frequency harmonics of twice the networking frequency. A traditional noise barrier is designed taking into account the strict size constraints imposed by technical compatibility with the electrical infrastructure, which limits its efficacy at low frequency. Noise masking with broadband signals can be a complementary solution to further reduce noise disturbance and contain it within prescribed limits. The evaluation of subjective response of the receivers to different mitigation solutions is made possible by the availability of the impulse response.

Investigation on an Absorbing Layer Suitable for a Noise-Reducing Two-Layer Pavement

Abstract: A polyurethane-based rubber-modified layer within a road superstructure leads to absorption of traffic emissions. Noise emissions have quite a negative effect on society, as they lead to high stress levels and health risks for people. Therefore, constructional methods of noise-reducing road layers have been developed before. This research paper focuses on the questions whether the existing noise-reducing road constructions, which have a low durability, can be optimized in terms of a longer duration while simultaneously maintaining the noise-reducing effects. Within this research, a large parametric study contributed to an optimal solution of a noise-reducing and durable layer. We found that noise absorption is mainly dependent of the void content of the pavement and its flexibility. Also, a result is that the durability of a road layer is based on the properties of the binder as well as the composition of the mixture, i.e., the grading curve. As we used polyurethane binders within our mixtures, which have a low dependency on regular environmental temperatures after their complete chemical reaction, we can imply a low temperature dependence of the entire polyurethane asphalt mixture. Based on these results, the construction of a noise-reducing and durable road layer is a great solution. The application of such road layers leads to lower traffic emissions at major hotspots. These might be urban highways, where the infrastructure is too tight to build noise barriers, enclosures or tunnels.

3D noise mapping for preselected locations of urban area with and without noise barriers: A case study of Delhi, India

Abstract: Abstract Noise pollution has been rising as a critical issue in recent days particularly for the people living in urban areas. This study has been conducted to find out the effects of traffic induced noise on nearby residential building through 3D noise mapping with and without noise Barriers. Monitoring has been carried out at various densely populated preselected locations of Delhi, India. Thereafter, 3D noise mapping has been done using hourly average noise levels for the locations exposed with maximum noise. The developed 3D noise map shows the variation of noise level along X, Y and Z direction for all selected locations before and after installation of noise barriers. Moreover, the result also shows that exact assessment of noise impact is possible through 3D noise mapping, when a multistory building close to the source of noise is taken into consideration. This paper also elaborates the adequate height, distance and NRC value of noise barrier to reduce the effect of road traffic noise on nearby high rise building. Reduction pattern of noise level can easily be visualized and evaluated by using these maps. This type of study could support decision makers during adaptation of suitable remedial measures.

The Potential of PV Noise Barrier Technology in Europe

Abstract: Photovoltaies is expanding into new market segments. Photovoltaic noise barriers (PVNB) along motorways and railways permit today one of the most economic applications of grid-connected PV w ith the additional benefits of large scale plants (typical installed power: more than 100 kWp) and no extra land consumption. The aim of this study is to reveal the large potential that can be exploited for PV on noise barriers with the overall objective of raising the share of renewable energies for the EU's electricity market. In contrast to many PV-potential studies published before, this proposal is focusing on PVNB only, as one of the cheapest ways to implement large scale grid-connected PV installations.

Finite Element Method for the Estimation of Insertion Loss of Noise Barriers: Comparison with Various Formulae (2D)

Abstract: Noise barriers are a critical part of noise mitigation in urban and rural areas. In this study, a comparison of the insertion loss calculations of noise barriers via the Finite Element Method (FEM) and various formulae (Kurze–Anderson, ISO 9613-2/Tatge, Menounou) is presented in the case of two-dimensional acoustic radiation problems. Some of the cases explored include: receiver in the illuminated zone, in the shadow zone, in the shadow border, source in medium, long, short distance from the barrier, source and receiver near barrier, and source above the barrier. Comparisons of the results indicate that FEM results comply well (less than 1 dB in each case) with Menounou’s formula which in turn complies with the analytic solution (MacDonald Solution). In certain cases, the differences between FEM and Menounou’s formula compared to Kurze–Anderson and ISO 9613-2/Tatge formulae are substantial (source and receiver near the barrier (10 dB) and source near the barrier and receiver in the shadow border (5 dB)). Similar differences are also confirmed by the analytic solution. The findings suggest that FEM can be applied effectively for the precise estimation of the insertion loss of noise barriers. Especially in cases where ISO 9613-2 formula shows large deviations from the analytic solution (e.g., near barrier), possible applications may arise in cases such as balconies, facades, etc. Furthermore, the study supports the idea that FEM could possibly be effectively utilized in real life applications for microscale urban acoustic modeling as a viable alternative to expensive noise prediction software.

Effects of the Top Edge Impedance on Sound Barrier Diffraction

Abstract: Sound barriers can be configured with different top edge impedance to improve their noise control performance. In this paper, the integral equation method was used to calculate the sound field of a barrier with various top edge impedance, and the effects of the barrier top edge impedance on sound barrier diffraction were investigated. The simulation results showed that the noise reduction performance of a sound barrier with a soft boundary on its top edge was larger than that with a hard boundary, but there were some impedance values which, if assigned to the top edge boundary, would give the sound barrier even better noise reduction performance. It was found that the sound barrier with a good top edge impedance formed a dipole-like radiation pattern above the barrier to expand the effective range of the shadow zone. The research discoveries reported in this paper point out the potentials of using acoustics metamaterials or active control methods to implement the desired good impedance on the top edge of a sound barrier for better noise reduction.

Effect of Landscape Elements and Structures on the Acoustic Environment on Wildlife Overpasses Located in Rural Areas

Abstract: The constantly growing number of motor vehicles increases the biodiversity conservation awareness of the public. To this end, numerous compensation measures are implemented, primarily provision of wildlife crossing infrastructure to guide animals over and under transport routes. There are different design aspects that must be considered in the case of wildlife crossings located in rural areas and in forests. An interdisciplinary approach should be employed for the wildlife crossing design, involving specialists from different fields of science. This article deals with the effect of local landscape elements and structures on the acoustic environment on the wildlife overpasses located in rural areas. Several tests were carried out, covering the levels of traffic, improvements around the existing overpasses and the noise distribution on them. For the final analysis, seven overpasses were chosen, differing in terms of the landscape elements and structures present. Five of them included noise barriers of different shapes and lengths and had a flat approach area. Two crossings did not have noise barriers and the approach areas were located in varied terrain. The analysis of the derived sound maps allowed for the determination of the effect of the different landscape elements and structures on the noise distribution on the overpasses under analysis. Earthen berms aligned with the noise barriers and extending to the length defined by the approach area topography were found to be the most effective noise-reducing measure.

Acoustic Barrier with Energy Harvesting

Abstract: The present article introduces a new type of piezoelectric barrier with energy harvesting elements. After modelling the noise barriers with COMSOL and conducting experiments, the location of the piezo elements for energy harvesting was determined. The purpose of this article is to test the efficiency optimization of the energy harvesting at noise reduction. The influence of three different typical types of acoustic spectra and different sound pressure levels on the generated electric energy were determined, as well as the efficiency of the acoustic noise power generation system at three different spectra and at different acoustic noise pressure levels on the acoustic barrier

Simulation-Based Optimisation for Urban Environmental Noise Coupled with Auditory and Visual Subjective Evaluation

Abstract: Environmental noise has a major negative impact, causing interference for people to communicate, rest, sleep, and general annoyance. In order to control urban environmental noise, simulation-based optimisation for urban environmental noise is conducted. On the basis of the current acoustic environment of Zhaohui Campus of Zhejiang University of Technology, three optimisation plans that include noise barrier optimisation, greenbelt optimisation, and a combination optimisation of noise barrier and greenbelt are proposed. These scenarios are simulated using NoiseSystem software to obtain their ability to reduce noise and determine auditory perception by using different control measures. To determine the visual perception of the optimisation plan, 100 people of different age groups were randomly selected, and each person scored the noise barrier and the greenbelt in the simulated scenarios. Results of the comprehensive evaluation of auditory and visual perception show that noise barriers can provide better auditory feelings, but greenbelts can provide a better auditory and visual subjective experience. Therefore, in addition to the application of noise control measures, their visual design must be fully considered. Moreover, the visual perception of plants is stronger than that of others.

Study of acoustic characteristics of noise barriers

Abstract: The acoustic efficiency of noise barriers has been studied using the developed two-dimensional finite element model in the COMSOL Multiphysics software package. Numerical calculations of the semi-infinite barrier efficiency have been compared with calculations conducted by the Maekawa formula. The main attention has been paid to the influence of the underlying surface on barrier acoustic characteristics. The barrier acoustic efficiency depends on its height, the position of the noise source and on the calculation point above the underlying surface. This dependence has been presented in this research.