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Train noise is a kind of green, non‐destructive and strong‐energy artificial seismic sources, which is widely used in railway safety monitoring, near‐surface imaging and urban underground space exploration. Distributed acoustic sensing is a new seismic acquisition technology, which has the advantages of dense sampling, simple deployment and strong anti‐electromagnetic interference ability. In recent years, distributed acoustic sensing has been gradually applied in the fields of urban traffic microseism monitoring, crack detection and underground space imaging. However, previous studies mainly focused on microseism interferometry using train event coda noise, and there is limited research on the workflow of interferometry imaging using distributed acoustic sensing–based heavy train events noise (with short coda windows), which produces an abundant of near‐source interference. Aiming at proving the effectiveness of this idea, we investigated a process workflow to get underground shear‐velocity structure based on distributed acoustic sensing recorded heavy traffic noise near Qinhuangdao train station. A weighted sliding absolute average method is used to weaken the strong amplitude to the coda wave level and reduce the near‐source influence. We demonstrated that the cross‐coherence interferometry method, after spectral whitening, has the best effect on sidelobe suppression in the virtual source surface wave shot gathers, through a comparative analysis of cross‐correlation and cross‐coherence results. For obtaining concentrated energy and strong continuity in phase velocity spectra, we selected the time windows with high spatial coherence and signal‐to‐noise ratio not less than 1.2 for stacking from 720 time windows in F–K domain. When dividing subarrays to extract pseudo‐two‐dimensional profile, we set the overlap rate between adjacent time windows to 80% to increase stacking times, enhancing the precision of phase velocity spectra and reducing the errors of picking dispersion curve. Our results show that heavy traffic train events noise (non‐pure coda) can be used to detect underground velocity structure with clear dispersion and high inversion reliability. This research provides a new processing flow for distributed acoustic sensing train noise imaging and can be applied in future urban underground space exploration. [ABSTRACT FROM AUTHOR]

Abstract Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains. For each piece of auxiliary equipment, the sound power measured on a test bench is combined with measured or predicted transfer functions. It is important, however, to allow for installation effects due to shielding by fairings or the train body. In the current work, fast-running analytical models are developed to determine these installation effects. The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing, using a barrier model. For equipment mounted under the train, the acoustic propagation from the sides of the source is based on free-field Green’s functions. The bottom surfaces are assumed to radiate initially into a cavity under the train, which is modelled with a simple diffuse field approach. The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green’s functions. Results show good agreement with a 2.5D boundary element model and with measurements. Modelling uncertainty and parametric uncertainty are evaluated. The largest variability occurs due to the height and impedance of the ground, especially for a low receiver. This leads to standard deviations of up to 4 dB at low frequencies. For the roof-mounted sources, uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations.

Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains. For each piece of auxiliary equipment, the sound power measured on a test bench is combined with measured or predicted transfer functions. It is important, however, to allow for installation effects due to shielding by fairings or the train body. In the current work, fast-running analytical models are developed to determine these installation effects. The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing, using a barrier model. For equipment mounted under the train, the acoustic propagation from the sides of the source is based on free-field Green's functions. The bottom surfaces are assumed to radiate initially into a cavity under the train, which is modelled with a simple diffuse field approach. The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green's functions. Results show good agreement with a 2.5D boundary element model and with measurements. Modelling uncertainty and parametric uncertainty are evaluated. The largest variability occurs due to the height and impedance of the ground, especially for a low receiver. This leads to standard deviations of up to 4 dB at low frequencies. For the roof-mounted sources, uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations. [ABSTRACT FROM AUTHOR]

Every ambient noise study employs the source-path-receiver structure to explore the overall behaviour of sound. Noise levels are affected by changes in distance, intervening barriers, and atmospheric conditions along the transmission path between the source and the receiver. The objective of this study is to quantify the influence of transmission path characteristics for a realistic time-varying moving line source. In this context, railway noise was considered to explore the variance of noise in an urban setting over a variety of measuring distances, including 25, 50, 100, and 200 m, with variables such as air temperature, humidity, and wind condition. The data corresponding to 106 trains was collected for analysis, and it was observed that the effect of the wind was more significant for larger distances between the source and the receiver. When the sound levels were measured in two opposite wind directions, a considerable noise level difference was observed. For every 1 m/s increase in wind speed, within a distance of 50 m, the average sound attenuation induced by the upwind phenomena was 0.2 dBA. The impact of air temperature changes on received sound level from a moving source was insignificant within the range of temperatures considered in the study. The effect of humidity is less at shorter distances but at larger distances, increasingly attenuates noise levels. Analysis of variance was performed on the selected variables to determine whether the means of each group were significantly different from each other and found that train speed had a more significant impact on railway noise compared to other parameters. [ABSTRACT FROM AUTHOR]

Sound propagation through turbulent boundary layer (TBL) is of great significance in transports where a TBL is attached to their external surfaces, for instance, air planes and high speed trains. Precise predictions of sound propagation through TBLs to their external surfaces can be extremely useful for their corresponding interior noise control. It is well known that a TBL is classified as an inhomogeneous flow medium and existing approaches are not capable to well predict its influence on sound propagation. Insight of sound propagation through TBLs is required but relevant research on this topic is limited in the literature. In this work, a modelling approach is developed to predict the influence of TBLs on sound propagation. In the proposed approach, the ray tracing method is employed to predict the evolution of sound waves when they are passing through a TBL, with which the equivalent phase speed of sound can be obtained and used to calculate the the Doppler factor so that the traditional methods can be extended to predict sound distribution in inhomogeneous flow media. The validation of this modelling approach is performed by using two cases. The first case is to predict the convective effect of sound propagation in a uniform mean flow and the predicted results are compared with analytical solutions. The second case is sound propagation through a TBL and the predictions obtained from this proposed approach are compared with numerical simulations obtained from the finite element (FE) method. In both cases, the convective effect obtained from this proposed approach is close to the analytical solution or the FE prediction. After that, the proposed approach is used to predict the sound propagation from a high speed train pantograph to the external surfaces of the train with considering the influence of the TBL. The corresponding results are verified by using FE simulations. This work shows that the proposed approach is effective and efficient, and also, it enhances the understanding of sound propagation in inhomogeneous flow media. [ABSTRACT FROM AUTHOR]

The subject of this paper is the long distance propagation of train noise. The sound exposure level of train noise L AE was measured. To describe the results of measurements, a semi-analytical model was used. It takes into account the wave-front divergence, air absorption, ground effect, and the turbulence destroying the coherent nature of the ground effect. The model contains three adjustable parameters that must be estimated at the site. To verify the model, we performed measurements of L AE at the distance D = 450 m from the train track center. The difference between the calculated and measured mean values of L AE equals 1.3 dB. [ABSTRACT FROM AUTHOR]

With the increasing requirement for the travelling comfort of high speed train, the reduction in interior noise becomes very important. Noise source identification is a prerequisite to the decrease in the interior noise. To study the effects of air conditioning system on the noise inside the high speed train, the comprehensive measurement of noise and vibration was made for different carriages of the high speed train. Analysis results of internal noise within different carriages in the running and static tests indicate that the air conditioning system has small effect on the interior noise and there are common significant characteristics of internal noise although the air conditioning systems within carriages are different. The main energy of internal noise is dominant in the low frequency range. The floor vibration excited by air conditioning system radiates the noise inside the carriage. [ABSTRACT FROM AUTHOR]

Abstract: Large-scale outdoor field measurements were carried out on a residential building to assess the noise levels caused by pass-by trains that run on a nearby viaduct. The experimental results were compared with different schemes for predicting noise from trains. The octave band sound power levels of the train passing by, which are required as input parameters for the Nordic prediction method for train noise (NMT), CSTB 92 and ISO 9613-2 provided in the Mithra software, were determined by an inversion method. The method of calculation of railway noise (CRN) from the UK gives the best agreement with the measured results. The NMT prediction scheme also provides a good prediction of the general trend of the experimental data, but it always overestimates the measured noise levels. As far as the quantitative agreement with experimental data is concerned, the CSTB 92 and ISO 9613-2 prediction schemes are comparatively less satisfactory. [Copyright &y& Elsevier]

This study developed a noise prediction model for elevated mass rapid transit (MRT) platforms. Relevant physical and operational parameters (e.g. cruise speed, acceleration and deceleration rates for trains, building fac¸ade setbacks and so on) were collected from the Bangkok mass transit system (BTS), the first elevated MRT system operated in Bangkok, Thailand. The equivalent continuous sound pressure levels (LAeq) were collected from both sides of the MRT stations at the center of each platform. The relevant parameters were collected on both platforms and ground level, on both sides of MRT stations. These parameters were statistically tested to determine their correlation with MRT noise. The final model was built from highly correlated parameters using multiple regression analysis with a stepwise regression technique. Statistical evaluation showed a high degree of goodness-of-fit test for the model to the observed data. Therefore, it can be efficiently used for the projection of MRT noise in the affected areas. [Copyright &y& Elsevier]

This paper analyses the interactions between vehicles, infrastructure and environment for rail traffic. It identifies variables having a significant influence on sound levels, defines a standard procedure for measuring noise, and develops a database for setting up and calibrating train noise models. A pilot study looks at two railway lines passing through Vercelli, a medium sized town in the north-west of Italy. Four main conclusions were drawn. First, in certain conditions, variables that normally influence noise production can be neglected (e.g. when surrounding environmental conditions are constant, different types of train do not cause a significant variation in noise level). Secondly, when diesel trains are travelling at less than 70 km/h, a speed change of 30–40 km/h significantly affects the maximum noise level (Lmax). However, for electrified lines, when speed is below 80 km/h, a change of 20–30 km/h does not cause significant variations in Lmax. Thirdly, for diesel trains transiting at low speeds––e.g. near stations––noise emissions are strongly affected by acceleration/deceleration. Lastly, an approach based on ‘sites types’ is able to produce useful results because site configuration and the presence of building significantly affect Lmax. High buildings along the line can increase noise levels and may nullify the advantages derived from technological advance in the vehicles. [Copyright &y& Elsevier]

Subways or rapid transit railways can be found in many major cities. These rapid transit railways are typically built above ground whenever possible to avoid the high capital cost of tunneling and also the high running cost of air conditioning and ventilation. However, noise from trains running on elevated tracks or viaducts close to residential and commercial buildings or houses is a problem for many cities. Noise barriers have been used extensively to mitigate noise from motorways, heavy trunk roads, and construction sites. On the other hand, relatively few reported studies on the design and performance of noise barriers for elevated railway tracks or viaducts to mitigate rapid transit train noise. The effectiveness of noise barriers on elevated railway tracks or viaducts for the mitigation of train noise may be different and challenging to predict due to complex street canyons and surrounding buildings beside the barrier designs and construction materials. Riding on the Singapore Railway Noise Barrier Programme, the present research conducted on-site measurements of several housing estates in Singapore to investigate the effect of noise barriers on the mitigation of train noise. Comparisons were also carried out to examine the performance of two different designs, Taiwan's Taipei subway track noise barriers and the vertical noise barriers used by the Singapore Mass Rapid Transit (MRT) system. Acoustic mapping revealed that the simulated noise mitigation barriers led to a 5–12 dB(A) reduction in noise levels reaching the resident apartments. [ABSTRACT FROM AUTHOR]

• Modelling approach for the noise beneath a train floor applied to rolling noise. • Direct and reverberant sound is calculated and relative contributions quantified. • The approach is verified by comparison with laboratory and field measurements. • Improved understanding of the acoustic behaviour beneath the train floor. An approach is presented for modelling the noise propagation beneath the train floor and this is applied to rolling noise sources. It is assumed that the sound incident on the train floor is made up of a direct and a reverberant component. A combination of two numerical modelling approaches is considered to deal with these: an equivalent source model, to represent the direct component, and statistical energy analysis (SEA) for the reverberant part. In the equivalent source model, the wheel is replaced by monopole and dipole sources, which represent its radial and axial radiation. The rail vertical vibration and the sleepers are replaced by arrays of monopole sources while the rail lateral vibration is replaced by an array of lateral dipoles. The sound power of the rolling noise is obtained by using the TWINS model. In the SEA model, the region beneath the train floor is divided into several volumes and the power input to these subsystems is assumed to be due to the first reflections from the train floor and the ground. The reverberant and direct sound have very similar contributions to the total sound power incident on the train floor although this depends on how the equipment is arranged beneath the train. The modelling approach is verified by comparing the predicted sound pressure levels with laboratory measurements and with field tests. [ABSTRACT FROM AUTHOR]

Aims: Some studies have suggested an association between noise exposure and hypertension. The hypothesis that prolonged exposure to train traffic noise causes high blood pressure was tested in a 4 years follow-up cohort study in population living in a dense traffic area, near a train station. Method: The study comprised two random samples of individuals aged 35-49 years. Study group included residents in the vicinity of train station (150 men) and 143 men from a quieter area of the same town. There was a continuous noise (level under 60 dB) and impulse interrupted noise exceeding 60 dB. Data were collected by use of a questionnaire and subjects were questioned about: heredo-colateral history of hypertension, smoking habits, the presence or absence of noise related to the profession, duration of living in the present home. After exclusion of those reporting an existing high blood pressure, or a professional exposure to noise at work, the final groups, consisted of 150 and 143 men, respectively, were seen in the initial cross-sectional phase and at follow-up intervals of 4 years. A general health questionnaire survey on community was conducted. There were questions regarding subjective symptoms, annoyance, sleep disturbance. The blood pressure was controlled twice a month. Results: The two groups were compared. Initial response rate was 65%. The groups were followed up every year, for 4 years. 73% of the original participants were followed up. 25% of the first group. exposed to noise, reported sleep disturbance, annoyance, headaches, nervousness and fatigue. 8% of them reported hypertension. Only 2 persons from the second group, unexposed to noise, had high blood pressure (1.4%). No convincing differences were seen in headaches, but the sleep quality was better and they did not complain so often of nervousness and fatigue. Discussions: A strong correlation was found between noise annoyance and psychological disturbance in the population living in a noisy area. Hypertension is more often present in subjects exposed to environmental noise. Conclusions: Our findings suggest that exposure to train intense traffic noise might be a risk factor for hypertension. A subsequent study of a larger group could clarify this finding. [ABSTRACT FROM AUTHOR]