Railway Rolling Noise Research Articles

Reply to Giannakos, K. Comment on: Toughness of Railroad Concrete Crossties with Holes and Web Openings. Infrastructures 2017, 2, 3

This paper responds to the discussion [1] by Dr. K. Giannakos over our technical note [2].[...]

Life cycle analysis of mitigation methodologies for railway rolling noise and groundbourne vibration

Negative outcomes such as noise and vibration generated by railways have become a challenge for both industry and academia in order to guarantee that the railway system can accomplish its purposes and at the same time provide comfort for users and people living in the neighbourhood along the railway corridor. The research interest on this field has been increasing and the advancement in noise and vibration mitigation methodologies can be observed using various engineering techniques that are constantly put into test to solve such effects. In contrast, the life cycle analysis of the mitigation measures has not been thoroughly carried out. There is also a lack of detailed evaluation in the efficiency of various mechanisms for controlling rolling noise and ground-borne vibration. This research is thus focussed on the evaluation of materials used, the total cost associated with the maintenance of such the measures and the carbon footprint left for each type of mechanism. The insight into carbon footprint together with life cycle cost will benefit decision making process for the industry in the selection of optimal and suitable mechanism since the environmental impact is a growing concern around the world.

The effect of temperature on railway rolling noise

The stiffness and damping of railpads in a railway track are affected by changes in the temperature of the surrounding environment. This results in the rolling noise radiated by trains increasing as the temperature increases. This paper quantifies this effect for a ballasted track equipped with natural rubber railpads and also studies the behaviour of a cork-reinforced rubber railpad. By means of measurements in a temperature-controlled environment, it is shown that the shear modulus of the natural rubber increases by a factor of six when the temperature is reduced from 40 ℃ to −20 ℃. The loss factor increases from 0.15 at 40 ℃ to 0.65 at −20 ℃. The shear modulus of the cork-reinforced rubber increases by a factor of 10, and the loss factor shows the typical trend of transition between rubbery and glassy regions. The railpad stiffness estimated from decay rate measurements at different temperatures is shown to follow the same trend. Field measurements of the noise from passing trains are performed for temperatures between 0 ℃ and 35 ℃; they show an increase of about 3–4 dB. Similar results are obtained from predictions of noise using the measured dependence of pad stiffness.

Noise reduction in urban LRT networks by combining track based solutions

The overall objective of the Quiet-Track project is to provide step-changing track based noise mitigation and maintenance schemes for railway rolling noise in LRT (Light Rail Transit) networks. WP 4 in particular focuses on the combination of existing track based solutions to yield a global performance of at least 6dB(A). The validation was carried out using a track section in the network of Athens Metro Line 1 with an existing outside concrete slab track (RHEDA track) where high airborne rolling noise was observed. The procedure for the selection of mitigation measures is based on numerical simulations, combining WRNOISE and IMMI software tools for noise prediction with experimental determination of the required track and vehicle parameters (e.g., rail and wheel roughness). The availability of a detailed rolling noise calculation procedure allows for detailed designing of measures and of ranking individual measures. It achieves this by including the modelling of the wheel/rail source intensity and of the noise propagation with the ability to evaluate the effect of modifications at source level (e.g., grinding, rail dampers, wheel dampers, change in resiliency of wheels and/or rail fixation) and of modifications in the propagation path (absorption at the track base, noise barriers, screening). A relevant combination of existing solutions was selected in the function of the simulation results. Three distinct existing solutions were designed in detail aiming at a high rolling noise attenuation and not affecting the normal operation of the metro system: Action 1: implementation of sound absorbing precast elements (panel type) on the track bed, Action 2: implementation of an absorbing noise barrier with a height of 1.10–1.20m above rail level, and Action 3: installation of rail dampers. The selected solutions were implemented on site and the global performance was measured step by step for comparison with simulations.

Sensitivity analysis of simulation model on railway rolling noise prediction

The railway rolling noise prediction software (RRNPS) is a simulation model for predicting the sound pressure levels during a train passage due to wheel/rail roughness, based on vibration dynamics, contact mechanics and sound radiation modules. Some field validation has been done under European and Australian conditions. Comparisons between simulations and measurements have shown that this software model gives reliable predictions in terms of overall A-weighted sound pressure level and noise spectrum. In this paper, based on a typical railway rolling noise situation in Australia (a series of field measurements were taken at a narrow track gauge testing site), a sensitivity analysis of the RRNPS was carried out to investigate the effect of train speed, normal load, sleeper spacing, rail pad stiffness, track gauge and rail cross receptance factor on railway rolling noise. The results provide some insight into model-based methods to control and mitigate railway noise at its source.

Validation of a prediction model for tangent rail roughness and noise growth

Railways can inevitably cause railway rolling noise, which is induced by both wheel and rail roughness. Due to the deformation and wear between the wheel/rail at the contact patch, the rail roughness may grow in amplitude after a number of wheelset passages. This results in increasing railway rolling noise. Rail roughness is a common aspect in all transit systems and much research has been pursued to predict and mitigate its growth on track but prediction of resultant noise growth has not been a focus. This paper provides the experimental validation of the modified Railway Rolling Noise Prediction Software (RRNPS) model for the prediction of rail roughness growth and corresponding noise growth. The model is a new framework to enable noise growth predictions due to rail roughness growth mechanics. It is validated by means of several experiments that have been performed along a straight railway line. Through comparisons between predictions and measurements, it is shown that the RRNPS model gives reliable predictions on rail roughness growth and corresponding noise growth. Subsequently this model is used to predict how speed, normal force, wheelset traffic and ballast vertical stiffness affect rail roughness growth and corresponding noise growth.

Railway rolling noise prediction: field validation and sensitivity analysis

The Railway Rolling Noise Prediction Software (RRNPS) is a model for predicting the sound pressure levels (SPLs) during a train passage due to wheel/rail roughness, based on vibration dynamics, contact mechanics and sound radiation modules. Similar software has been developed previously, in particular the Track–Wheel Interaction Noise Software (TWINS) model, and some field validation has been done under European and Japanese conditions. In this article, the RRPNS is used to model a typical railway rolling noise situation in Australia and compared with detailed field experimental results for validation purposes. A series of field measurements were taken at a narrow track gauge testing site in Australia. Comparisons between simulations and measurements have shown that this software model gives reliable predictions in terms of overall A-weighted SPL and noise spectrum. In addition, a sensitivity analysis of the model was carried out to investigate the effect of speed, normal load, ballast vertical stiffness, rail pad vertical stiffness and rail cross receptance factor on railway rolling noise. This article extends the range of conditions for which the software model has been validated and gains some confidence in its use. It also provides some insight into model-based methods to control and mitigate railway noise.

Effects on short pitch rail corrugation growth of a rail vibration absorber/damper

Rail corrugation growth is related to the wheel–track dynamics and uneven wear on the rail head. The so-called pinned–pinned resonance of track vibration is considered as the cause of short pitch rail corrugation that is associated with railway rolling noise generation. A promising measure for reducing railway rolling noise is by the use of rail vibration absorber/damper. Reduction of 5–6 dB in the rail radiated noise can be achieved using rail vibration absorber/damper. In addition a rail vibration absorber/damper is found to be able to suppress the pinned–pinned resonance, and thus, its use may lead to attenuate formation of short pitch rail corrugation. In this work the effects of rail vibration absorber on short pitch rail corrugation growth are studied by combining the wheel–track-absorber dynamics, rolling contact mechanics and wear. The evolution process of rail corrugation is simulated and the results show that short pitch rail corrugation, whose wavelength is associated with the pinned–pinned resonance, is effectively suppressed by a rail vibration absorber. The use of rail vibration absorber has both immediate and long term effect on the railway rolling noise control, i.e. reducing the rail radiation and attenuating growth of short pitch rail corrugation, respectively.

The influences on railway rolling noise of a rail vibration absorber and wave reflections due to multiple wheels

A compound track-absorber model is employed to study the effect of multiple wheels and rail vibration absorbers on a rail, one of the main parts that generate rolling noise. Effects are wave reflections induced by multiple wheel—rail interactions and the increase in the decay rate of vibration along the rail by using a rail absorber. The rail vibration and noise radiation owing to a roughness excitation are studied by comparing the results of calculations with and without rail absorbers and multiple wheels in turn (i.e. four situations in all). These results are given in terms of vibration energy and sound power levels, and a comparison is made between tracks in four situations. Theoretical predictions show that multiple wheels and rail absorbers have significant effects on the rail receptance, the wheel—rail interaction force, and the vibration decay rate along the track. In addition, the influence of multiple wheels on the energy and noise is limited, whereas that of the rail absorbers is notable. The rail component of rolling noise can be reduced by 7.3 dB(A) by using the rail absorber. However, multiple wheels have a slight effect on the rail radiation.

A waveguide finite element and boundary element approach to calculating the sound radiated by railway and tram rails

Engineering methods for modelling the generation of railway rolling noise are well established. However, these necessarily involve some simplifying assumptions to calculate the sound powers radiated by the wheel and the track. For the rail, this involves using an average vibration together with a radiation efficiency determined for a two-dimensional (2D) problem. In this paper, the sound radiation from a rail is calculated using a method based on a combination of waveguide finite elements and wavenumber boundary elements. This new method allows a number of the simplifying assumptions in the established methods to be avoided. It takes advantage of the 2D geometry of a rail to provide an efficient numerical approach but nevertheless takes into account the three-dimensional nature of the vibration and sound field and the infinite extent of the rail. The approach is used to study a conventional ‘open’ rail as well as an embedded tram rail of the type used for street running. In the former case it is shown that the conventional approach gives correct results and the complexity of the new method is mostly not necessary. However, for the embedded rail it is found that it is important to take into account the radiation from several wave types in the rail and embedding material. The damping effect of the embedding material on the rail vibration is directly taken into account and, for the example shown, causes the embedded rail to radiate less sound than the open rail above about 600 Hz. The free surface of the embedding material amplifies the sound radiation at some frequencies, while at other frequencies it moves out of phase with the rail and reduces the radiation efficiency. At low frequencies the radiation from the embedded rail resembles a line monopole source which produces greater power than the ‘open’ rail which forms a line dipole.

Testing a new rail roughness measurement standard

Railway rolling noise arises from the combined roughness of the wheel and rail surfaces. The rail roughness is therefore an important parameter in the assessment of train pass-by noise. The Technical Specifications for Interoperability (TSI's) in Europe require noise to be measured on a 'reference track' the conditions of which are controlled. A spectral limit for the rail roughness is a major part of that control. The TSIs needed a new standard for rail roughness measurement so the CEN commissioned TC 256 Working Group 3 to draft one. The final draft of the new standard is now complete and will soon be published. This paper describes a 'road test' that was part of the standard development process. This test involved asking eight teams from all over Europe with seven different instruments to measure roughness at the same site, independently making their own interpretation of the standard. The paper outlines the aims of the new standard and describes the road test. It presents results and conclusions of the test that have been used already to improve the standard. Consideration had to be made of how rail-head defects are treated and how different measurement technologies are used.

A tuned damping device for reducing noise from railway track

A promising means to reduce the component of railway rolling noise radiated by the track is to increase the damping of the rail. This increases the attenuation with distance of vibrations transmitted along the rail and thereby reduces the noise radiated. To achieve this, a tuned, damped mass-spring absorber system has been designed. To cover a wide range of frequencies, multiple tuning frequencies are used along with a material with a high damping loss factor. Suitable materials have been found from extensive tests on samples and prototypes of the damper have been built and tested, both in the laboratory and in the field. Results are very promising with reductions of the track component of noise of around 6 dB being measured.

A full-scale test rig for railway rolling noise: simulation and measurement of dynamic wheelset–track interaction

A new outdoor rolling-noise test rig on a 25 m stretch of full-scale track will enable the study of vibrations of wheel and rail and of the pertinent noise emission under controlled conditions. The arrangement can be seen as a physical realization of the Track–Wheel Interaction Noise Software (TWINS) computer software. The track and wheel, which are not in mechanical contact, are excited in vertical and lateral directions using electrodynamic actuators. The track can be statically pre-loaded by up to 30 tonnes. The use of the rig is presently under development. The aim is that the radiated noise from separate railway components could be found as the wheel and the track can be excited both together and separately. Amplitude and phase of the applied forces are predetermined by use of an algorithm taking into account the real wheel–rail interaction properties. In that way different wheel–rail contact conditions can be simulated. Eight partners have co-operated in the development and operation of the CHARMEC/Lucchini Railway Noise Test Rig in Surahammar, Sweden. In ongoing experiments, the dynamics of both the wheel and rail have been examined in the frequency domain. For the track, comparisons have been made between data obtained from the rig and those from field measurements on a standard Swedish line. Both dynamic response and spatial decay rates have been studied. The performance of the rig has also been compared to results from TWINS and to results from the literature. Good agreement was obtained in the frequency range from 100 to 5000 Hz. Some results from preliminary measurements of noise emission will be given.

Extended validation of a theoretical model for railway rolling noise using novel wheel and track designs

A theoretical model for railway rolling noise, TWINS, was first developed some years ago and was previously validated against field measurements for conventional wheel and track designs. This model has subsequently been used in the design of noise-reducing wheels and tracks. An outcome of the recent Silent Freight and Silent Track projects was a series of novel designs that were tested in a comprehensive field experiment. Alongside this development, the theoretical model has been updated to improve accuracy and include new features. The results of 34 wheel/track combinations that were measured in field experiments are compared with corresponding predictions using the improved model. It is found that the mean difference between measured and predicted overall A-weighted sound pressure levels is less than 2 dB while the standard deviation is 1.9 dB. The improved accuracy of the model is also shown by a reanalysis of the original validation experiments.

The effects on railway rolling noise of wave reflections in the rail and support stiffening due to the presence of multiple wheels

Theoretical models that describe the high frequency dynamic behaviour of railway track, are applied to study two effects of the presence of multiple wheels on the rail. These are the influence of wave reflections in the rail induced by the multiple wheel/rail interactions and the local stiffening of the support due to the preload induced by the vehicle weight. Results are given in terms of overall track vibration, sound power spectra and A-weighted levels, and a comparison is made between tracks with three different types of rail pad. The results show that the preloading and wave reflections have significant effects on the rail receptance and the wheel/rail interaction force, but that their influence on the overall track vibration and noise radiation are limited to about 1 dB(A) for two of the three pads considered. For the track with soft pads that is considered, the track noise would be over-predicted by about 3 dB(A) if these effects were not included.

Model-based acoustic substitution source methods for assessing shielding measures applied to trains

A promising means of reducing the rolling noise from trains is local shielding in the form of vehicle-mounted shrouds combined with low trackside barriers. This is much less visually intrusive than classic lineside noise barriers. Various experimental methods have been proposed that allow the performance to be assessed under static conditions, enabling rapid comparisons of different configurations. This paper focuses on acoustic substitution source methods and their application to the noise radiated from the wheel. The vibrating wheel can be represented by a set of acoustic point sources at its surface. Modal behaviour of the wheel is simulated by applying appropriate phase relations between the acoustic point sources. Transfer functions between the point sources and microphone positions at the trackside are measured reciprocally. By comparing measurements of these transfer functions with and without the shielding devices installed, an insertion loss spectrum can be obtained. To calculate the reduction of the total pass-by noise, the acoustic point source contributions need to be weighted appropriately for which the TWINS calculation model for railway rolling noise is used. The performance of the method has been investigated for a closely mounted wheel skirt.

VIBRATION ANALYSIS OF RAILWAY TRACK WITH MULTIPLE WHEELS ON THE RAIL

The major source of railway rolling noise is the structural vibration of the wheel and rail which is generated by the combination of small-scale undulations (roughnesses) on the wheel and rail contact surfaces. Usually, the rail vibration behaviour is studied using a model in which only a single wheel is present. This is not the case in practice, where multiple wheels roll on the rail. It is shown first that the high-frequency excitation from each wheel can be treated independently by using the superposition principle, provided that the rail vibration is considered as a frequency band average. The appropriate application of the superposition principle is then to model the rail vibration as a sum of cases in which all wheels are retained in contact with the rail but the roughness at all but one of them is set to zero. The presence of multiple wheels on the rail leads to reflections of waves in the rail. The paper explores such effects on the rail vibration caused by multiple wheels acting as supplementary dynamic systems. The receptance of a rail with a single additional wheel on it is studied first to acquire a physical insight into the effects of wheels on the rail vibration. Then more complicated models are developed and used to investigate the effects of multiple wheels on a rail. Practical consequences due to the multiple wheel–rail interactions are also presented.

EXPERIMENTAL CHARACTERIZATION OF WHEEL AND RAIL SURFACE ROUGHNESS

For several years, studies carried out in Europe have shown the need to consider wheel and rail surface roughness as a major excitation parameter in railway rolling noise. Measuring the rail roughness may be critical in the assessment of the noise created by the wheel/track system. It can be measured by means of two complementary methods:The direct scanning method allows a spectral representation of roughness levels that can be strongly influenced by the applied data processing. It must include the removal of sharp spikes resulting from pits or spikes, which are not representative of the actual excitation of the wheel/rail system.

The effects of rail support stiffness on railway rolling noise

Rolling noise from trains is radiated by both wheel and track vibrations, the track being dominant in many cases. The stiffness of the rail fastener system, especially the elastomeric rail pad usually inserted between the rails and the sleepers, has a significant influence on the noise emitted by the track. Railways are increasingly using softer pads to reduce potential damage to sleepers and ballast. Softer pads decouple the rail from the sleeper. This reduces the noise from the sleeper but also reduces the decay of vibration with distance along the rail and hence leads to an increase of the noise radiated by the rail. The paper describes experimental and theoretical work to investigate the influence of pad stiffness on the dynamic and acoustic behavior of track. The vibrational behavior has been measured on a dedicated 36-m section of railway track, with different types of rail pad installed. The results are compared with predictions using theoretical models of the track behavior. This allows the effective pad stiffness and damping to be determined, laboratory measurements also being available for comparison. The attenuation of vertical and lateral vibration along the track is measured in order to estimate the effect on radiated noise.

THE EFFECTS OF LOCAL PRELOAD ON THE FOUNDATION STIFFNESS AND VERTICAL VIBRATION OF RAILWAY TRACK

Track vibration is one of the main sources of railway rolling noise. The resilient components in the railway foundation such as the pad and ballast have significant effects on the track vibration. Usually, their parameters vary with load and frequency. The wheel load of a train causes local deformation in the track and the foundation, so the railpads and the ballast are preloaded and thus their stiffness has different values at the supports near the wheel load from the other supports. In this paper the preloads in the pad and ballast caused by a single wheel load are studied by considering the non-linear properties of the track foundation, and thus the preload pad and ballast stiffnesses are determined. A model of the track dynamics based on an infinite discretely supported Timoshenko beam with preloaded pad and ballast dynamic stiffness is developed. Its vertical vibration behaviour under the influence of the local wheel load is investigated. It is shown that the point receptance for vertical vibration is strongly affected by the local wheel load at low frequencies, but the effect of the local wheel load on the average wave propagation decay rate along the rail is very limited.