Noise Barriers Research Articles

Investigation of the Variation in Insertion Loss of Vertical Noise Barriers for High-speed Railways at Different Levels of Sound Transmission Loss

Abstract The present study investigates the impact of sound transmission loss of vertical noise barriers for high-speed railways on insertion loss at various speed grades and heights. The findings reveal an initial increase in insertion loss followed by a plateau as sound transmission loss improves. A threshold value exists for weighted sound transmission loss, beyond which the insertion loss remains relatively constant. This threshold referred to as the minimum weighted sound transmission loss decreases with increasing train speeds and increases with higher noise barrier heights. The variation in insertion loss was calculated for noise barriers at heights of 2m and 3m under different sound transmission loss conditions, using measured sound source data corresponding to train speeds of 150km/h, 200km/h, 250km/h, 300km/h, and 350km/h. By polynomial fitting, at a train speed of 400 km/h, the minimum weighted sound transmission loss for 2m and 3m high noise barriers are determined to be 20dB and 21dB respectively.

Analysis of train-induced aerodynamic characteristics and pressure-relief measures relating to fully enclosed noise barriers installed on railway bridges

Fully enclosed noise barriers (FENBs) are increasingly being installed on high-speed railway bridges for noise pollution control. However, the aerodynamic effects of high-speed trains passing FENBs have an adverse impact on barrier durability and generate micro-pressure waves. In this paper, a numerical model of a train passing an FENB on a bridge is established. The aerodynamic pressure distribution along the FENB is analyzed for both a single train and two trains passing one another. The propagation characteristics and evolution mechanisms of pressure waves are then investigated. The results show that the pressure is lower at the ends of the FENB and higher in the middle along the direction of train travel. The peak positive and negative pressures at the mid-span are 1.95 and 4.47 times higher than those at the ends, respectively. This distribution is caused by the propagation, superposition, reflection, and attenuation of pressure waves. Compression waves account for 78.9% of the peak positive pressure. An amplification factor must be considered when estimating the impact of two trains passing one another. Analysis of five pressure-relief schemes shows that arranging a single pressure-relief hole at a high-pressure location effectively alleviates the over-pressure in the FENB. The overall pressure-relief effect is an exponential function of the single opening area. Considering a constant opening area, arranging several relief holes at equal spacing optimizes the adverse pressure distribution compared with the single-hole relief scheme. The equivalent forces of the multi-hole scheme are 3.35% and 7.58% lower than in the single-hole scheme.

Simulation Analysis of Influence Laws of Sound Barrier Acoustic Performance When Using Ceramic as Sound-absorbing Materials

Abstract The excellent sound absorption performance of Sound Barrier which using Ceramic as Sound-absorbing Materials can be attributed to their corrosion resistance, lightweight nature, small particle size, and internal microporous structure. As a result, the application of new ceramic-based sound absorption materials in sound barriers is becoming increasingly widespread. To address the challenging issue of predicting the sound absorption and isolation performance of ceramic sound barriers and understanding the influencing factors on acoustic parameters, a simulation analysis method was employed for analyzing and studying various factors affecting the acoustic performance of these barriers. The calculation results demonstrate that increasing the thickness of both the sound absorption material and air layer behind exhibits similar effects on enhancing the sound absorption and isolation performance of ceramic acoustic barriers. Specifically, increasing either parameter leads to improved sound absorption performance by significantly increasing the sound absorption coefficient at 125Hz and 250Hz while decreasing it at 500Hz. However, in high-frequency bands above 1000Hz, structural parameters have minimal overall influence. Moreover, when keeping the thickness of ceramic sound absorption plates constant, every additional 20mm increase in air layer thickness behind results in a weighted increase in sound isolation by approximately 1dB; notable improvements are observed when this air layer thickness is below 1600Hz. When the thickness of the air layer behind is kept constant, an increase in the thickness of the sound absorption material by 10mm results in a 1dB increment in weighted sound isolation. However, when maintaining a total thickness of the sound barrier at 140mm, increasing the material’s thickness leads to a reduction in air layer thickness. Consequently, there is a slight enhancement in the sound absorption coefficient at frequencies of 125Hz and 250Hz while a minor decrease occurs at frequencies of 500Hz and 1000Hz. The impact on other frequency bands and overall sound absorption performance remains inconspicuous. Moreover, variations in weighted sound insulation quantity have minimal influence on sound insulation characteristics.

Study of Acoustic Barriers with an Cylindrical Top Edge for Reducing the Noise of Power Equipment

Study of Acoustic Barriers with an Cylindrical Top Edge for Reducing the Noise of Power Equipment

Time-domain model for spherical wave reflection in a flat surface with absorber character – Application to the SOPRA measurement method

This paper presents a developed time-domain model for the reflection of spherical waves in an absorber-like surface. The model is made to enable evaluation of measurement methods for assessing the sound absorptive properties of traffic noise barriers in direct sound field, it is thus called the Direct Field Absorption (DFA) model. In this study, the DFA model is applied to the in-situ SOPRA method for quick sound reflection index measurements on road noise barriers. The DFA model results in an impulse response (IR), based on a theoretically derived impedance of a certain absorber. The DFA IR is entered to the SOPRA formula to calculate the reflection index, RIQ, of the absorber, which is subsequently compared to the measured RIQ of a wall fitted with the absorber in question. If the results are similar, it is reasonable to assume that the SOPRA measurement results are valid. But if there are any significant differences between the DFA and SOPRA sound reflection indices, possible reasons for them should be examined.The first results are encouraging, showing that the DFA model can be a valuable tool to evaluate the results of reflection measurements. Furthermore, the DFA model could be useful for estimating the sound absorptive performance at lower frequencies of a noise barrier limited to its spatial extent in width and height, i.e., when it is physically impossible to measure. Further studies are necessary though, since the conclusions of this paper are based on only one kind of absorber.

A Review of Urban Planning Approaches to Reduce Air Pollution Exposures.

With only 12% of the human population living in cities meeting the air quality standards set by the WHO guidelines, there is a critical need for coordinated strategies to meet the requirements of a healthy society. One pivotal mechanism for addressing societal expectations on air pollution and human health is to employ strategic modeling within the urban planning process. This review synthesizes research to inform coordinated strategies for a healthy society. Through strategic modeling in urban planning, we seek to uncover integrated solutions that mitigate air pollution, enhance public health, and create sustainable urban environments. Successful urban planning can help reduce air pollution by optimizing city design with regard to transportation systems. As one specific example, ventilation corridors i.e. aim to introduce natural wind into urban areas to improve thermal comfort and air quality, and they can be effective if well-designed and managed. However, physical barriers such as sound walls and vegetation must be carefully selected following design criteria with significant trade-offs that must be modeled quantitatively. These tradeoffs often involve balancing effectiveness, cost, aesthetics, and environmental impact. For instance, sound walls are highly effective at reducing noise, provide immediate impact, and are long-lasting. However, they are expensive to construct, visually unappealing, and may block views and sunlight. To address the costly issue of sound walls, a potential solution is implementing vegetation with a high leaf area index or leaf area density. This alternative is also an effective method for air pollution reduction with varying land-use potential. Ultimately, emission regulations are a key aspect of all such considerations. Given the broad range of developments, concerns, and considerations spanning city management, ventilation corridors, physical barriers, and transportation planning, this review aims to summarize the effect of a range of urban planning methods on air pollution considerations.

A review of ventilated acoustic metamaterial barriers

A review of ventilated acoustic metamaterial barriers

Noise barriers as a mitigation measure for highway traffic noise: Empirical evidence from three study cases

Noise barriers are path interventions between noise sources and human receivers used mainly along road corridors to improve the acoustic environment for affected residents. Despite their widespread use, the impact of these interventions on community perception is still insufficiently investigated. This paper presents findings from a longitudinal study evaluating the efficacy of noise barriers in three residential areas alongside highways, compared to a reference case in a relatively quiet area. Noise exposure was objectively quantified via acoustic measurements and noise modelling, while socio-acoustic surveys measured the residents' subjective response in terms of noise annoyance as well as other aspects of quality of life. While noise exposure (Lday) decreased on average by 4.4–11.7 dBA at near-barrier points, direct reductions in pre to post-intervention noise annoyance were observed only in one case. Additionally, only in this particular case were the appraisals of the acoustic environment restored to a condition similar to low-level noise emissions (reference case). Contextual factors potentially downgrading the interventions' effectiveness are discussed, such as the history of complaints and coping, mistrust towards road authorities, high expectations, and the impacts of the COVID-19 pandemic. While noise exposure reductions did not directly lead to noise annoyance decreases, an ordinal regression pooling all cases revealed that larger reductions in noise exposure were associated with a higher likelihood of residents reporting decreased traffic noise annoyance in the post-survey. No evidence was found regarding noise barriers’ impact on the subjective assessment of other aspects of quality of life, such as health complaints, concentration disturbance, and sleep quality.

Aerodynamic discrepancies of high-speed trains meeting within two types noise barriers: considering modeling scale ratio

PurposeSustainable urban rail transit requires noise barriers. However, these barriers’ durability varies due to the differing aerodynamic impacts they experience. The purpose of this paper is to investigate the aerodynamic discrepancies of trains when they meet within two types of rectangular noise barriers: fully enclosed (FERNB) and semi-enclosed with vertical plates (SERNBVB). The research also considers the sensitivity of the scale ratio in these scenarios.Design/methodology/approachA 1:16 scaled moving model test analyzed spatiotemporal patterns and discrepancies in aerodynamic pressures during train meetings. Three-dimensional computational fluid dynamics models, with scale ratios of 1:1, 1:8 and 1:16, used the improved delayed detached eddy simulation turbulence model and slip grid technique. Comparing scale ratios on aerodynamic pressure discrepancies between the two types of noise barriers and revealing the flow field mechanism were done. The goal is to establish the relationship between aerodynamic pressure at scale and in full scale.FindingsThe aerodynamic pressure on SERNBVB is influenced by the train’s head and tail waves, whereas for FERNB, it is affected by pressure wave and head-tail waves. Notably, SERNBVB's aerodynamic pressure is more sensitive to changes in scale ratio. As the scale ratio decreases, the aerodynamic pressure on the noise barrier gradually increases.Originality/valueA train-meeting moving model test is conducted within the noise barrier. Comparison of aerodynamic discrepancies during train meets between two types of rectangular noise barriers and the relationship between the scale and the full scale are established considering the modeling scale ratio.

Design optimization of floor plan for public housing buildings in Hong Kong with consideration of natural ventilation, noise, and daylighting

Indoor environmental quality plays a crucial role in determining the overall quality of life. This study aims to develop a design optimization approach for the floor plan of public housing buildings with modular flat design in Hong Kong, with focus on enhancing natural ventilation, reducing noise levels, and improve daylighting conditions. The evaluation of these environmental factors was conducted using deep neural network models and a mathematically based Calculation of Road Traffic Noise model. A general floor plan representation was developed for three- and four-winged structures of public housing buildings. An optimization approach utilizing Bayesian optimization was applied to three studied cases: Hung Shing House, Hung Hei House, and Cheung Tai House. The optimization process resulted in an average 41.5 % improvement in average natural ventilation rate. The optimized building shapes effectively served as noise barriers, leading to an average reduction of 20 % in average noise levels. The existing window configurations of each unit type under the modular flat design already provided sufficient daylighting, resulting in only a minor improvement from the optimization process.

Noise control strategies: Options beyond sound walls

As noise control requirement needs expand into different and new industries, traditional "sound walls" are becoming less utilized and there is a focus more on treating source noise with products specifically designed for various applications considering frequency content, low frequency impacts, intermittent noise and tonal content. This presentation will explore feasible and efficient noise control strategies and applications, focusing on both temporary and permanent solutions that address a variety of industries, along with new product lines that are available to provide solutions where either "sound walls" are not applicable or site constraints require an outside the box approach to provide solutions. Attendees will learn about engineered applications for both environmental and interior industrial impacts across various industries and challenges and what solutions are available that consider feasibility, safety, access and performance while also considering cost implications.

Thinking inside the box: a cost-effective approach to fan array noise reduction

Noise from fan arrays can contribute high sound pressure levels both to buildings and communities. Noise that travels from these units through ducts and into the spaces within buildings can be attenuated with silencers or duct lining. However, sound radiated from the unit through building structures or into communities can be more difficult to attenuate and often adds significant cost. While it is possible to attenuate sound from the unit using enclosures or sound walls, exploring the operation of the fan arrays themselves could be a more cost-effective noise reduction method. One particular noise reduction method for an existing fan array was proposed for a customer: review sound levels of each fan within the array to determine how they are contributing to the radiated sound power level of the unit. The assumption that sound levels between individual fans within fan arrays are consistent is not always correct. A series of acoustical tests were completed; results indicated that sound caused by turbulent airflow within the tested fan array was able to be lowered by reducing the fan speeds of individual fans. By reducing the fan speeds of problematic fans and increasing speeds for the quieter ones within the same fan array, the same level of cooling can be provided with lower overall radiated sound levels at no additional cost.

How can optimized forest management plan regulate noise levels from wind turbines?

Wind energy has emerged as one of the most economically viable renewable energy options in the transition towards a fossil-free society. In Finland, wind farms, consisting of several wind turbines, are commonly located in forested areas, prompting concerns about their potential audio-visual impacts. Despite this, research into how forests might mitigate the adverse effects of wind farms are limited. Forests can effectively serve as noise barrier, with their noise attenuation capacity varying based on the forest’s characteristics. Specifically, the attenuation level depends on the sound’s travel distance through the forest, as well as the size and density of trees. Our study findings indicate that forests can provide up to 10 dB of additional noise attenuation. This was achieved by integrating a forest structure-based model into forest planning calculations, aimed at mitigating noise pollution from wind turbines. Incorporating this noise model as a management objective significantly reduced noise levels in the pilot study area, outperforming traditional business-as-usual management strategies. Furthermore, adapting a combination of uneven-aged and even-aged forest management approaches resulted in more forested landscape, which was more effective in mitigating higher noise levels. Our results contribute important insights that, along with further research, can guide future forest planning and management towards enhanced sustainability.

Improving Traffic-noise-mitigation Strategies with LiDAR-based 3D Tree-canopy Analysis

The leaves on trees absorb road noise and serve as noise barriers. Tree structures such as tree belts and isolated trees have various methods for absorbing sounds. The depth, surface area, and noise-absorption coefficient of trees contribute to noise absorption. Therefore, this study aims to address this issue of traffic-noise pollution through the use of trees; in particular, by analyzing the noise-absorption coefficient of leaves, the surface area of the leaves, and the depths of the trees. However, the study stresses the need for 3D tree-canopy visualization to identify these factors. To achieve this, the study used LiDAR point clouds to provide accurate data for the convex hull visualizations of canopies. Additionally, a formulated equation for calculating traffic noise after absorption has been suggested by combining the traffic-noise absorption and Henk de Kluijver traffic-noise models. The study also compares the effectiveness of tree belts and isolated trees in reducing noise pollution, concluding that, below a canopy of trees, there is no noise reduction. Finally, the study has demonstrated that the number and sizes of leaves affect noise absorption, showing that noise pollution can be reduced by 1 to 3 dB(A) in the research area by using trees.

Numerical simulation of train-induced aerodynamic pressure on railway noise barriers

Numerical simulation of train-induced aerodynamic pressure on railway noise barriers

Closing the Loop in the Process of Manufacturing Noise Barriers and Floating Trash Barrier - Case Study

The circular economy embodies a contemporary approach centered on sustainability and waste reduction, gradually integrating into production and consumption practices. Nonetheless, it has often remained a theoretical or abstract concept across various economic sectors. This paper focuses on the potential implementation of circularity principles, using the production process of noise barriers, manufactured by the production company based in Prešov, Slovak Republic, as an illustrative example. Through a comprehensive case study, it was determined that reintegrating generated waste into the production cycle is feasible. Moreover, there is potential for a cascading effect, where original waste could be utilized across multiple production processes. This underscores how the circular economy fosters economic efficiency, innovation, and creativity in diverse areas such as design, product diversification, input sourcing, and production planning. The paper's significance lies in its thorough examination of the production process, quantifying various types of waste to uncover innovative methods of converting waste into new input materials. Additionally, it offers insights and actionable guidance towards embracing multicircularity (via a circularity spiral), along with strategies for identifying opportunities to incorporate circularity elements into production schemes. This approach promises extensive economic, environmental, and social benefits, considering product nature and usage.

Hands-on Learning Pedagogy in Teaching Concepts Relevant in the Analysis, Design, and Maintenance of Transportation Infrastructure Systems

Learning critical concepts that are centered on the analysis, design, and maintenance of transportation infrastructure systems poses a measure of difficulty for undergraduates in engineering. Therefore, hands-on learning pedagogy should be an excellent precursor to increase understanding of these concepts, since the pedagogy incorporates real-life experience in the delivery. This paper describes how a hands-on learning pedagogy called experiment-centric pedagogy (ECP) has been used to teach these concepts to undergraduate students at a historically Black university. The research questions are as follows: (1) How well can ECP improve students’ understanding of concepts essential to the analysis and design of transportation infrastructure systems? (2) How has the ECP facilitated the achievement of the learning objectives of these concepts? and (3) Does an ECP increase the engagement of undergraduate students in their transportation infrastructure engineering learning and lead to measurable lasting gains? To answer these research questions, ECP was implemented and assessed when used to teach the concepts of stress and strain utilized in the analysis of bridges and other transportation infrastructure, sound used in the development and design of noise barriers, moisture content in controlling compaction of highway infrastructure systems, and degradation of infrastructure systems exposed to various environmental settings. Assessment results from 92 undergraduates reveal an increase in students’ motivation and cognitive understanding of the relevant concepts, as well as learning gains and an improved success rate compared to the traditional method of teaching.

Modified calculation model of train-induced aerodynamic pressure on vertical noise barriers considering the train geometry effect

High-speed trains (HSTs) generate air disturbance, leading to significant aerodynamic pressure on the noise barriers. Differences in train geometry result in variations in the aerodynamic pressure on noise barriers, implying that existing European standard calculation models may not necessarily be suitable for all types of HSTs. In this paper, the influence of the width, height, and nose length of the train on the aerodynamic pressure on vertical noise barriers was studied using computational fluid dynamics (CFD) simulations. Results showed that taller and wider trains result in greater aerodynamic loads on noise barriers. Conversely, an increase in the nose length of a train leads to a reduction in such pressure. Using grey relational analysis, correlation of various factors with the train-induced aerodynamic pressure is, from strong to weak: distance to the track center, width, height, and nose length of the train. Building upon the EN 14067-4 calculation model, the shape coefficients of trains with varying geometric characteristics were derived using the simulation data obtained in this study. A modified pressure calculation model was established accounting for the differences in geometric features of HSTs and pressure distribution in the vertical direction of noise barriers and validated using relevant data from the literature.

The Use of Wind Turbine Blades to Build Road Noise Barriers as an Example of a Circular Economy Model.

This project's objective was to create a circular economy in the composites sector by examining the possibility of using wind turbine blade composite materials to construct noise-absorbing barriers for roads. The possibility of constructing road noise barrier panels from components obtained from turbine blades was conceptually examined, and the geometry and construction of wind turbine blades were evaluated for their suitability as filler components for panels. The tensile strength parameters of two types of composites made from windmill blades-a solid composite and a sandwich type-were established based on material tests. The strength of the composite elements cut from a windmill propeller was analyzed, and a three-dimensional numerical model was created using the finite element method. The strength values of the composite used to construct the noise barriers were compared with the stresses resulting from loads operating on the road noise barriers, as determined in compliance with current standards. It was discovered that acoustic screens composed of composite materials derived from wind turbine blades may withstand loads associated with wind pressure and vehicle traffic with sufficient resistance. In order to evaluate the environmental benefits resulting from the use of composite material made from wind turbine blades to make noise barriers, this study presents the values of the embodied energy and embodied carbon for several types of road noise barriers using life cycle assessment.

Strategic Planning Approach for Noise Control in Urban Areas

Cities, accommodates more than half of the world population, contributes a major role in overall global development. However, the urban environment has its own challenges, and most prevalent issue is noise pollution, and it is described as a contemporary plague. This problem is linked to various health issues in public like depression, fatigue, insomnia, headaches, and decreased concentration etc. Compounding the issue is the cumulative impact of noise, where the detrimental effects may not manifest immediately. The study emphasizes the critical need for strategic planning approach and the measures to tackle various urban noise sources. The study also focuses into existing policies and guidelines on noise control in Indian urban context and explores different noise analysis approaches and regulations of other countries through case studies. The analysis delivers a set of recommendations on reducing noise pollution through noise zoning, based on the case studies. These recommendations range from the installation of noise barriers along transportation corridors to the implementation of zoning regulations that segregate noisy industrial or commercial activities from residential areas. Additionally, the study advocates for the establishment of strict noise limits tailored specifically for road traffic, underlining the pivotal role of well-designed public transport systems. This not only help in reducing noise impacts but also promotes sustainable urban development. Overall, the study attempts to create quieter, healthier sustainable urban spaces.