Railway Noise Research Articles

Railway Noise Pollution: An Investigation of Rail Systems in Terms of Noise Pollution Regulations and Land Usage

Noise pollution caused by transportation has become problem for societies with increasing traffic volumes and the development of cities day by day. In European countries and Turkey, transportation-related noise pollution has caused health problems as well as reducing the living standards of the people. It is necessary to carry out detailed studies in order to determine the problems caused by noise pollution, especially in the regions where industry and labor force are concentrated, and to solve these problems. The city of Izmir is one of the cities where the noise caused by the railway needs to be investigated. As a result of the studies carried out in the research area, the railway noise pollution map was created with the IDW method with the data obtained from 8 different points. Afterwards, the effect of railway systems on the land usage types of cities, noise pollution problems, and the period between 2000-2018 were examined. The negative effects of noise pollution caused by the railway in the hinterland of the suburban line in the study area and its effect on the land usage type were investigated with the EU and Turkey Noise Regulation and the land cover data of the European Environment Agency.

Hypertension, a linchpin between environmental noise exposure and the development of cardiovascular disease?

Environmental noise exposure has been considered one of the most common hazards worldwide, especially in the workplace environment, and could produce a variety of health issues. Some epidemiological evidence supports the association between occupational noise exposition and a high risk for hypertension and cardiovascular diseases. Wang etal. has conducted an observational cross-sectional study using occupational data of 4746 workers, 32.4% were exposed to high occupational noise. These exposed individuals had a moderate increase in the risk for hypertension (adjusted odds ratio [OR], 1.30; 95% confidence interval [CI], 1.05-1.62). The subgroup analyses showed that the relationship between noise and hypertension prevalence was stronger in young participants (OR, 1.70; 95% CI, 1.21-2.40). Noise exposure activates the sympathetic and endocrine systems producing an increase in blood pressure and the changes in other biological risk factors. Moreover, a recently published study showed that oxidative stress and DNA damage were significantly higher in subjects exposed to noise. Emotional stress reactions and unconscious physiological stress could also be potential mechanisms for hypertension. Finally, physiological stress caused by noise exposure may also increase indulgence in unhealthy behaviors, such as smoking and alcohol consumption, and indirectly result in an increased risk of hypertension and cardiovascular diseases. Previously published studies showed relationships between environmental noise exposure (including road traffic, railway, and aircraft noises) and the development of hypertension and cardiovascular diseases. Thus, the study by Wang etal. emphasizes the importance of environmental control in the prevention of cardiovascular diseases, not only in the workplace but also outside it.

Estimation of the dynamic stiffness of railway ballast over a wide frequency range using the discrete element method

Ballast is an integral part of railways, serving as a load transfer medium between the rails and the subgrade. In analytical modeling of track dynamics, ballast is idealized as a spring with constant stiffness at all excitation frequencies, which is a reasonable assumption for studying track dynamics at low frequencies up to 100 Hz. For modeling railway noise, the frequency dependency of ballast stiffness and damping at high frequencies is of utmost importance. Since ballast is a granular material whose properties depend on the packing, density and size distribution of the particles, the discrete element method is a promising tool for determining the frequency-dependent ballast stiffness. In the current work, a novel approach is presented to determine the frequency dependency of dynamic stiffness of the ballast used by the Swiss Federal Railways, using Discrete Element Method (DEM). First, a characterization of the Hertzian contact parameters required for modeling the ballast is performed. The effectiveness of the discrete element method for modeling the dynamic behavior of the ballast is evaluated by comparing the results obtained from our calculations with experimental results obtained under two different boundary conditions. The evaluated dynamic stiffness varies significantly with the frequency of excitation, especially above 100 Hz. The validated DEM model is then used to determine the effects of preloads on the dynamic stiffness.

Cardiovascular consequences of aircraft noise exposure.

The results from epidemiological studies suggest that environmental noise including aircraft, railway, road traffic, wind turbine, and leisure-related noise is a growing public health concern. According to the WHO, at least 100 million people in the European Union are affected by traffic noise levels above the WHO-recommended thresholds. Environmental noise can adversely affect physical and mental health, as well as wellbeing. Chronic low-level noise exposure typical for most environmental sources is associated with psychophysiological stress causing non-auditory or indirect noise effects leading ultimately to cardiovascular diseases. Among all environmental noise sources, aircraft noise is considered the most annoying, and its leading mechanism of action is autonomic system activation such as increases in heart rate and blood pressure. Previously, we observed that long-term exposure to aircraft noise was associated with increased diastolic blood pressure, arterial stiffness (as assessed by pulse wave velocity), and impaired left ventricular diastolic function. All mentioned above effects are early, subclinical, and potentially reversible changes which preceded late noise effects in the cardiovascular system, that is, established cardiovascular diseases such as myocardial infarction, stroke, and heart failure. However, even a short-term reduction in aircraft noise exposure as observed during the COVID-19 lockdown may reverse these negative effects on arterial stiffness and blood pressure and may decrease the prevalence of insomnia. In this review, we aimed to critically discuss our obtained results considering recent studies on the influence of aircraft noise (and other traffic noises) on cardiovascular diseases in the context of the WHO Environmental Noise Guidelines for the European Region.

Dose-response association between transportation noise exposure and type 2 diabetes: A systematic review and meta-analysis of prospective cohort studies.

To examine the longitudinal association between transportation noise exposure (road traffic, aircraft, and railway noise) and T2D in a meta-analysis. We systematically searched PubMed, Embase, Scopus, Cochrane, and Web of Science published up to February 2022. The GRADE approach was used to evaluate the study quality, and the pooled effect estimate was calculated by the fixed-effects model or the random-effects model. We included 10 prospective studies with a total of 4,994,171 participants and 417,332 T2D cases in the meta-analysis. According to the Navigation guide, 8 studies out of 10 were rated as having a probably high or high risk of bias. For road noise, the pooled relative risk (RR) per 10dB higher Lden for developing T2D was 1.06 (95% CI:1.03, 1.09) with high heterogeneity (I2 =90.1%, p<0.001). Similar associations were also observed in aircraft and railway noise: the pooled RR were separately were: 1.01 (1.00, 1.01) and 1.02 (1.01, 1.03) separately. A 'dose-response' analysis found a similar linear association between road noise exposure and the risk of T2D. An overall 6% increase in the risk of T2D per 10dB increase in road exposure was observed. Further studies are needed to confirm our findings, especially for aircraft and railway noise, and to identify the mechanisms involved.

Long-term exposure to transportation noise and risk of type 2 diabetes: A cohort study

BackgroundSome studies have found transportation noise to be associated with higher diabetes risk. This includes studies based on millions of participants, relying entirely on register-based confounder adjustment, which raises concern about residual lifestyle confounding. We aimed to investigate associations between noise and type 2 diabetes (T2D), including investigation of effects of increasing confounder adjustment for register-data and lifestyle. MethodsIn a cohort of 286,151 participants randomly selected across Denmark in 2010–2013 and followed up until 2017, we identified 7574 incident T2D cases. Based on residential address-history for all participants linked with exposure assessment of high spatial resolution, we calculated 10-year time-weighted mean road and railway noise at the most (LdenMax) and least (LdenMin) exposed façades and air pollution (PM2.5). We used Cox models to calculate hazard ratios (HR) with increasing adjustment for individual- and area-level register-based sociodemographic covariates, self-reported lifestyle and air pollution. ResultsWe found that a 10 dB increase in 10-year mean road LdenMin was associated with HRs (95% CI) of 1.06 (1.02–1.10) after adjustment for age, sex and year, 1.08 (1.04–1.13) after further adjustment for register-based sociodemographic covariates, 1.07 (1.03–1.12) after further lifestyle adjustment (e.g. smoking, diet and alcohol) and 1.06 (1.02–1.11) after further PM2.5 adjustment. For road LdenMax, the corresponding HRs were 1.07 (1.04–1.10), 1.05 (1.02–1.08), 1.04 (1.01–1.07) and 1.03 (1.00–1.06). Railway noise was associated with HRs of 1.04 (0.98–1.11) for LdenMax and 1.02 (0.92–1.12) for LdenMin after adjustment for sociodemographic and lifestyle covariates and PM2.5. ConclusionsLong-term exposure to road traffic noise was associated with T2D, which together with previous literature indicates that T2D should be considered when calculating health impacts of noise. After sociodemographic adjustment, further lifestyle adjustment only changed HRs slightly, suggesting that large register-based studies with adjustment for key sociodemographic covariates can produce reliable results.

Effects of railway noise and vibrationson dissatisfaction of residents: case study of Iran.

In this study, the effects of noise and vibrations caused by railways on the lives of residents around the railways in districts 17 and 18 of Tehran, the capital of Iran which amounts to about 700,000 people, are investigated. In the first stage the actual level of noise was measured at various points which showed above standard levels. Afterward, the authors developed a questionnaireand the survey was conducted from 376 residents. The findings of this study show that the most important factor for the residents adjacent to the railway line is the need for action by the country's railway authorities to reduce and control the adverse effects of noise and vibration. Also, the analysis of inferential statistics performed by chi-square test shows that the variables of gender and proximity of residence or workplace or both to the railway do not affect any of the railway noise or vibration dissatisfaction. The age variable also has no effect on noise dissatisfaction but does impact on vibration. Finally, distance from the railway affects both disaffection from noise and vibration.

Comparative Analysis of Dynamic Responses of Different Types of High-Speed Railway Noise Barriers under the Influence of Fluctuating Wind Pressure

The fluctuating wind pressure generated when a high-speed train passes through the noise barrier will cause deformation and damage to the noise barrier, affecting the safety of train operation and causing serious economic losses. In this paper, a research method for the dynamic response of noise barriers is proposed, and a comparative study of vertical noise barriers and semi-enclosed noise barriers is carried out. The study shows that when trains pass through the noise barrier, the fluctuating wind pressure on the surface of the two different types of noise barriers both exhibit the characteristics of head and tail waves; the time course curve of fluctuating wind pressure has the same change rule, the wind pressure reaches the maximum value at the bottom measuring point, the maximum value of fluctuating wind positive pressure and negative pressure of the semi-closed noise barrier is larger than that of the vertical noise barrier. In terms of natural frequency, the natural frequency range of the vertical noise barrier is 16~85 Hz, and the natural frequency range of the semi-enclosed noise barrier is 3~13 Hz. The natural frequency of the semi-enclosed noise barrier partially coincides with the main frequency of fluctuating wind pressure, which may lead to resonance damage. When the train speed is raised from 200 km/h to 350 km/h, the maximum equivalent force of the semi-enclosed noise barrier reaches 17.21 Mpa, which is much larger than the maximum equivalent force of the vertical noise barrier. At the same time, the displacement of the two noise barriers increases with the height of the noise barrier, and the maximum displacement of the semi-closed noise barrier unit board reaches 3.63 mm, which is much larger than that of the vertical noise barrier unit board.

Suicide and transportation noise: a prospective cohort study from Switzerland

Background: Evidence for effects of transportation noise on mental health remains scarce, mainly due to a lack of high quality studies. Meanwhile, psychiatric diseases are among the most prevalent non-communicable diseases worldwide, and suicide as a mortality outcome presents a pressing public health issue. The aim of this study is to investigate the association between transportation noise and suicide, while adjusting for air pollution. Methods: Road traffic, railway and aircraft noise exposure as well as PM2.5 exposure were linked to 5.1 million participants 15 years or older in the Swiss National Cohort, accounting for their address history. Mean noise exposure in 5-year periods was calculated. Individuals were followed for up to 15-years (2001-2015). Time-varying Cox regression models were applied to total suicides and cause-specific suicide deaths. Models included all three noise sources, PM2.5 plus individual and spatial covariates including socio-economic status. Effect modification by sex was also explored. Results: During the follow-up, there were 11,265 suicide deaths. Road traffic and railway noise were associated with total suicides (Hazard ratio: 1.039 [95% CI: 1.015-1.064] and 1.022 [1.004-1.041] per 10dB Lden, respectively ), while no significant association was found for aircraft noise. Associations were stronger for females than males. The pattern was robust across all outcomes, with the strongest association seen in non-violent suicides (poisoning: HR 1.122 [1.042-1.209] per 10dB Lden road traffic noise). No robust association was observed for PM2.5, whether adjusted for noise or separately. Conclusion: In this longitudinal, nationwide cohort study, we report a robust association between exposure to road traffic and railway noise and an increased risk for death by suicide. These findings add to the growing body of evidence that mental health disorders may be related to transportation noise exposure. Keywords : road traffic, railway, aircraft, Lden, air pollution, mental health

Long-term exposure to transportation noise and risk of type 2 diabetes: a cohort study

BACKGROUND AND AIM A few studies have reported associations between transportation noise and diabetes. This includes studies based on millions of participants, relying entirely on register-based confounder adjustment, which raises concern about residual confounding from lifestyle. We aimed to investigate associations between road and railway noise and risk of type 2 diabetes (T2D), including investigation of effects of increasing adjustment for register-based and lifestyle covariates. METHODS In a population-based cohort of 324,988 participants randomly selected across Denmark in 2010–2013 and followed up until December 2017, we identified 7,574 incident T2D cases using hospital and prescription registries. Based on historical address-information, we calculated 10-year time-weighted exposure to road noise at the most (LdenMax) and least (LdenMin) exposed façades and exposure to air pollution (PM2.5). We used Cox proportional hazards models to calculate hazard ratios (HR) with increasing adjustment for individual- and area-level register-based sociodemographic covariates (e.g. education and income) and lifestyle covariates assessed through questionnaires, including smoking, physical activity and alcohol. RESULTS We found that a 10 dB increase in road LdenMin was associated with HRs (95% CI) of 1.06 (1.02–1.10) in the crude model, 1.08 (1.04–1.13) after adjustment for register-based sociodemographic covariates and 1.07 (1.03–1.12) after further adjustment for lifestyle. For road LdenMax, the corresponding HRs were 1.07 (1.04–1.10), 1.05 (1.02–1.08) and 1.04 (1.01–1.07). After further adjustment for PM2.5, HRs were 1.06 (1.01–1.10) for LdenMin and 1.03 (1.00–1.07) for LdenMax. Railway noise was associated with HRs of 1.05 (0.98–1.11) for LdenMax and 1.04 (0.94–1.14) for LdenMin in fully adjusted models. CONCLUSIONS Long-term exposure to road and potentially railway noise was associated with T2D. Our results indicated that administrative cohort studies can produce reliable results if a broad register-based adjustment strategy is applied. KEYWORDS Road noise; railway noise; type 2 diabetes; lifestyle

Noise effects on health in studies in Low-Middle-income-countries (LMICs): a mapping review update of epidemiological evidence

Background and Aim: Noise has been linked to adverse non-auditory health problems, including annoyance, sleep disturbance, cardiovascular disease, and impaired cognitive function. However, most studies on these topics have been conducted in developed countries. This review focussed on studies in Low-and Middle-income-countries (LMICs), where populations are exposed to relatively higher levels of noise Methods: We conducted a literature search of Medline and Web of Science from 2009-2021 for studies in LMICs investigating environmental noise ((including road traffic noise, railway noise, aircraft noise, community noise, wind turbine noise, etc.) effects on health (including annoyance, cardiovascular disease, mental health condition). Results: Fifty-six papers were included in the review. Thirty-four (60.7%) of the 56 studies assessed exposure based on fixed-site sound level meter, thirteen with noise mapping, six with subjective ratings, three with personal monitoring. The mean level of noise exposure among all the reviewed studies ranged from 36.6 dB to 121.2 Db. Twenty-two (39.3%) of the 56 studies looked at noise annoyance and perception and found, as with non-LMIC studies, higher noise levels are associated with higher annoyance. Eleven studies examined cardiovascular outcomes reported that short-term noise exposure may slightly increase blood pressure among children and long-term noise exposure was linked to higher prevalence of hypertension and coronary artery disease in adults. Studies on all other outcomes remain very limited which preclude a meaningful synthesis of the findings. Conclusion: To our knowledge, this is the first review to summarize current evidence on the relationship between noise exposures and health outcomes in LMICs. This review provides critical and concise evidence on the knowledge gap to inform the future research agenda to help better understand noise pollution and human health in a global context. Keywords: Noise; Health; Low-and Middle-income-countries (LMICs)

Rail traffic noise-induced nocturnal awakenings might lead to depression and anxiety disorder – Results of the Leipzig LIFE cohort study

Background and Aim Recent studies found elevated depression risks for people exposed to traffic noise. In the LIFE cohort-study, we analysed the relationship between &amp;#x22;awakenings” induced by maximum railway-traffic noise levels and affective disorders. Methods Based on the 5-year-follow-up of the Leipzig LIFE cohort study (n=5679 participants), we examined the relationship between address-specific rail traffic noise-induced &amp;#x22;awakenings” and depression (incidence of 5.3% applying the CES-D scale) as well as anxiety disorder risks (incidence of 4.9% applying the GAD-7 scale). We converted maximum noise pressure levels induced by railroad noise into awakening probabilities according to Möhler et al. (2018), and we summed up the individual awakening probabilities to get the total number of nocturnal awakenings. Thus, for example, if the awakening probability for the passage of a freight train is 5.7%, then approximately 18 train passages would result arithmetically in 1 awakening. Results An increase in depression risk for &amp;#x2265;3 nocturnal awakenings was found (incidence rate ratio IRR=1.86; 95% 0.63-5.52, adjusted for gender, age and socioeconomic status) for rail traffic noise. The risk of depression reached statistical significance if people with missing values for depression at baseline were included. The risk of an incident anxiety disorder was increased due to an exposure of &amp;#x2265;3 awakenings due to rail traffic noise (IRR=2.56; 95% CI 1.02-6.43). Conclusions Increased risks for anxiety disorders (and less pronounced for depression) were found for &amp;#x2265;3 nocturnal awakenings due to rail traffic noise. Noise protection measures should take into account the reduction of maximum rail traffic noise levels to in turn reduce nocturnal awakenings. Keywords: rail traffic noise, maximum noise levels, nocturnal awakenings, depression, anxiety disorder, cohort study Acknowledgments: This study was supported by German Environment Agency (UBA). References Möhler U, Schreckenberg D, Müller U et al. Maximalpegelkriterien für die Beurteilung von Schienenverkehrslärm in der Nacht. Larmbekämpfung 2018;13:15-22.

Moving model test on the aerodynamic pressure of bilateral inverted-L-shaped noise barriers caused by high-speed trains

With the increasing speed of high-speed trains, the aerodynamic impact of trains on high-speed railway noise barriers has gradually become a focus of attention. Compared with traditional vertical noise barriers, the bilateral inverted-L-shaped noise barrier (BILSNB) has better noise insulation performance, but its aerodynamic impact may be more prominent. In this research, a moving train-BILSNB test system with a scale ratio of 1:16.8 is established, and the influence of train speed and the opening width on the aerodynamic pressure is analysed and discussed. The large eddy simulation is applied to investigate the influence mechanism of flow field on the aerodynamic performance of the BILSNB. The main conclusions are as follows. (1) The pressure amplitude caused by the passing of the train head is 36.67% greater than that generated by the passing of the train tail on average. (2) The maximum pressure of the BILSNB appears at the bottom area. When the height of the measuring point increases from 0.5H to 1.6H, the pressure coefficient of peak positive pressure, peak negative pressure and pressure amplitude decrease by 29.0%, 17.0% and 15.5%, respectively. (3) The aerodynamic pressure in the BILSNB has a longitudinal end effect: the pressure coefficient of positive peak pressure and pressure amplitude at the inlet section are 27.6% and 17.5% higher than the corresponding average value of all middle sections, respectively. (4) The pressure amplitude of the BILSNB is approximately proportional to 2.15 power of the train speed. The pressure coefficient of the BILSNB is approximately a power function of the opening width, and the value range of the index is about (−0.26, −0.30). (5) The mechanism of the longitudinal end effect is as follows: When the train arrives at the inlet section, the high-speed airflow in front of the train head cannot flow around in time resulting in the impact effect of the airflow on the inlet section becomes greater than that on the middle section. The influence mechanism of the opening width is as follows: The narrower the opening width is, the more intense the airflow inside the BILSNB is compressed, and the impact effect of the airflow on the noise barrier is more significant.

Environmental Noise and Effects on Sleep: An Update to the WHO Systematic Review and Meta-Analysis.

Background:Nighttime noise carries a significant disease burden. The World Health Organization (WHO) recently published guidelines for the regulation of environmental noise based on a review of evidence published up to the year 2015 on the effects of environmental noise on sleep.Objectives:This systematic review and meta-analysis will update the WHO evidence review on the effects of environmental noise on sleep disturbance to include more recent studies.Methods:Investigations of self-reported sleep among residents exposed to environmental traffic noise at home were identified using Scopus, PubMed, Embase, and PsycINFO. Awakenings, falling asleep, and sleep disturbance were the three outcomes included. Extracted data were used to derive exposure–response relationships for the probability of being highly sleep disturbed by nighttime noise [average outdoor A-weighted noise level () 2300–0700 hours] for aircraft, road, and rail traffic noise, individually. The overall quality of evidence was assessed using Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) criteria.Results:Eleven studies ( responses) were included in addition to 25 studies ( responses) from the original WHO analysis. When sleep disturbance questions specifically mentioned noise as the source of disturbance, there was moderate quality of evidence for the probability of being highly sleep disturbed per 10-dB increase in for aircraft [; 95% confidence interval (CI): 2.01, 2.36], road (; 95% CI: 2.28, 2.79), and railway (; 95% CI: 2.57, 3.43) noise. When noise was not mentioned, there was low to very low quality of evidence for being sleep disturbed per 10-dB increase in for aircraft (; 95% CI: 1.20, 1.93), road (; 95% CI: 1.08, 1.21), and railway (; 95% CI: 0.91, 1.49) noise. Compared with the original WHO review, the exposure–response relationships closely agreed at low (40 dB ) levels for all traffic types but indicated greater disturbance by aircraft traffic at high noise levels. Sleep disturbance was not significantly different between European and non-European studies.Discussion:Available evidence suggests that transportation noise is negatively associated with self-reported sleep. Sleep disturbance in this updated meta-analysis was comparable to the original WHO review at low nighttime noise levels. These low levels correspond to the recent WHO noise limit recommendations for nighttime noise, and so these findings do not suggest these WHO recommendations need revisiting. Deviations from the WHO review in this updated analysis suggest that populations exposed to high levels of aircraft noise may be at greater risk of sleep disturbance than determined previously. https://doi.org/10.1289/EHP10197

Demiryolu yuvarlanma yüzeyi gürültüsü ve zemin titreşimi ve hat ilişkili azaltma önlemleri-güncel gelişmeler

Railway Noise and vibration pollution affect millions of people globally, especially those who live close to or near the railway line. Although railway transportation mode is known as environmentally friendly technology, its contribution to noise pollution is no less a degree. Many experimental and observational studies show an adverse effect of noise and vibration on human well-being. The primary purpose of this paper is to overview the source of railway noise caused by primary sources, mainly rolling noise and ground vibration, and the development of recent railway noise mitigation measures in consideration from a track-related perspective.

Subsampling bootstrap in network DEA

Data Envelopment Analysis (DEA), provides an empirical estimation of the production frontier, based on an observed sample of decision making units (DMUs). Except for the single input-single output case, the asymptotic distribution of the DEA estimator can only be approximated through bootstrapping approaches. Therefore, bootstrapping techniques have been widely applied in the DEA literature to make statistical inference for the cases when the production process has a single-stage structure. However, in many cases, the transformation of inputs into outputs has an inner structure that needs to be considered. This paper examines the applicability of the subsampling bootstrap procedure in the approximation of the asymptotic distribution of the DEA estimator when the production process has a network structure, and in the presence of undesirable factors. Evidence on the performance of subsampling bootstrap is obtained through Monte Carlo experiments for the case of two-stage series structures, where overall and stage efficiency estimates are calculated using the additive decomposition approach. Results indicate great sensitivity both to the sample and subsample size, as well as to the data generating process. Subsampling methodology is then applied to construct confidence interval estimates for the overall and stage efficiency scores of railways in 22 European countries, where the railway transport process is decomposed into two stages and the railway noise pollution problem is considered as an undesirable output.

Traffic Noise Reduction Strategy in a Large City and an Analysis of Its Effect

A noise reduction strategy was proposed for Panyu District of Guangzhou City based on its traffic noise map, which considered both road and railway traffic noise. Commercial software was applied to compute the noise maps with and without noise barriers based on the field traffic flow measurements. Noise compliance maps were further developed to assess the effects of noise barriers on the quality of the sound environment. The change in populations exposed to unhealthy traffic noise with noise barriers was calculated, and the group noise indicators Gdn and Gnight, which indicate the populations of highly annoyed and sleep-disturbed people, were evaluated. The results showed that the traffic noise level was significantly decreased after the implementation of noise barriers. It was predicted that with the strategy of applying suitable noise barriers, the overall areas under heavy noise pollution could be reduced by 24.5 and 24.3 km2 during daytime and nighttime, respectively. Meanwhile, the total areas that could meet the regulated standard for noise levels were increased by 97.4, and 66.9 km2, corresponding to compliance rate increments of 18.38% and 12.62%, respectively, in daytime and nighttime. The results further revealed that the installation of noise barriers could significantly reduce the population of highly annoyed people, while the reduction of the population experiencing sleep disturbances was insignificant.

Evaluating railway noise sources using distributed microphone array and graph neural networks

Identifying and evaluating railway noise sources is beneficial for establishing more targeted suppression and mitigation strategies. This paper proposes a novel approach to evaluate dominant railway noise sources for all bogie regions, by using an array of microphones and a physics-informed graph neural networks (GNN) model. The GNN model encodes not only the acoustic data collected by the microphone array but also the spatial relationship between noise sources and microphones, and it also considers the physical background of sound in terms of Doppler effect and acoustic attenuation . In-situ measurements of railway noises have been taken on an operating metro line to train and validate the GNN model which exhibits satisfactory performance in evaluating the noise sources of interest. The proposed approach enables a more flexible and cost-effective microphone array implementation strategy in comparison to the commonly adopted commercialized acoustic beamforming system.

Improving strategic noise mapping of railway noise in Europe: Refining CNOSSOS-EU calculations using TWINS

The Environmental Noise Directive (2002/49/EC) requires all European Union Member States to produce strategic noise maps using a common assessment methodology: CNOSSOS-EU. The reliability of CNOSSOS-EU railway noise evaluation is dependent on the input vehicle and track transfer functions. The CNOSSOS-EU default database contains the currently available choices for these transfer functions. However, these available transfer functions are limited and of insufficient quality, resulting in large errors in noise level calculations. An approach is presented, introducing an established analytical railway rolling noise calculation technique (TWINS), to extract more reliable and specific transfer functions. A case study consisting of railway rolling noise mitigation measures is defined and used as the basis for extracting and testing these transfer functions. The extracted transfer functions reduce the average deviation between CNOSSOS-EU and reference calculations using TWINS from 6.1 dB(A) to 0.8 dB(A) in absolute sound power levels, and from 1.2 db(A) to 0.3 dB(A) in estimates of noise reduction potential for the defined mitigation measures. Application of this approach shows potential to improve the quality and depth of the existing CNOSSOS-EU default database. This may lead to more reliable estimations of railway noise in the strategic noise maps and the subsequent assessment of its harmful effects.

Sound absorption characteristics of surface perforated mortar with micro-sized pores

Surface perforated mortar (SPM) is a cement-based acoustic material that can reduce railway noise. SPM has macro-sized holes on its surface, and the geometry of the holes influences the majority of the absorption performance of SPM. A previous study achieved a higher sound absorption performance than that of traditional pervious concrete by attenuating the resonance caused by the holes. Given that most of the acoustic materials are porous, it was hypothesized that micro-sized pores can enhance the sound absorption performance of SPM. Therefore, this paper exploits aluminum powder as a foaming agent for cement and investigates the effect of the micro-sized pores on the sound absorption of SPM. An in-situ sound absorption test results revealed that incorporating micro-sized pores in SPM improves the sound absorption performance by 133%. The frequency range of sound absorption is mainly dependent on the geometry of the macro-sized holes, and the amount of micro-sized holes affects the degree of sound absorption. Based on the experimental studies on the effects of the geometry of the macro-sized holes and the amount of the micro-sized holes, the design guidelines for SPM are proposed.