Rolling Noise Research Articles

Railway noise and the effect of top of rail liquid friction modifiers: changes in sound and vibration spectral distributions in curves

For railway noise in curves, both flanging and squeal noise can be environmentally significant. Rolling noise is dominant in tangent track. This paper examines the spectral sound distribution in curves for different wheel/rail system types, and compares spectra after the top of rail friction level is controlled with a special friction modifier. The friction modifier controls top of rail (TOR) friction at an intermediate level, and imparts “positive friction” attributes to the interfacial layer. A significant range of spectral characteristics was noted for the different wheel/rail system types. In all cases the friction modifier significantly reduced the sound levels at the frequencies associated with top of rail squeal, and also at the frequency bands related to flange contact noise. For some Metro systems a noticeable reduction was also recorded at the lower frequencies associated with rolling noise, possibly due to a reduction in “graunching”. There was some suggestion of reduction at low frequency vibration (frequencies down to 30 Hz) as well as in the high stick-slip oscillation frequencies.

A theoretical study for the propagation of rolling noise over a porous road pavement

A simplified model based on the study of sound diffracted by a sphere is proposed for investigating the propagation of noise in a hornlike geometry between porous road surfaces and rolling tires. The simplified model is verified by comparing its predictions with the published numerical and experimental results of studies on the horn amplification of sound over a road pavement. In a parametric study, a point monopole source is assumed to be localized on the surface of a tire. In the frequency range of interest, a porous road pavement can effectively reduce the level of amplified sound due to the horn effect. It has been shown that an increase in the thickness and porosity of a porous layer, or the use of a double layer of porous road pavement, attenuates the horn amplification of sound. However, a decrease in the flow resistivity of a porous road pavement does little to reduce the horn amplification of sound. It has also been demonstrated that the horn effect over a porous road pavement is less dependent on the angular position of the source on the surface of tires.

Analysing the tyre-road rolling noise with a measurement vehicle

The European Union has set itself the goal of halving traffic noise by 2020. After measures taken at the drive train, further reductions will only be forthcoming in the field of vehicle tyres in future. To measure the tyre-road noise, a suitable tyre-testing vehicle based on the BMW 5-Series was developed at the Institut für Kraftfahrwesen Aachen (ika). This was done on behalf of TÜV Automotive GmbH.

한국형 고속철도의 소음 전파특성에 관한 연구

In order to control the railway noise, the radiation characteristic of the noise when the train passes by should be analyzed. Generally, the major noise sources of the Korea Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, a train model that is considered to be a row of point sourcesis introduced to analyze the radiation characteristic. The analysis results are compared with the measurement ones. It is shown that the propagation characteristic of the rolling noise is a dipole type and the noise generated by the power unit is radiated as a cosine type. With increasing of the train speed, the noise level at a receiving point is increased in the direction of motion and reduced in the direction opposite to the motion. The analysis results including the moving effect of the noise source at 300km/h show good agreement with the measurement results.

Development of a digital ambulatory recording system for electrodermal activity

A digital ambulatory recording system of electrodermal activity (D-EDA) that uses a multimedia card (MMC) as a compact data storage device was developed. Low power consumption allows 24 h simultaneous recording of skin conductance and/or skin potential. A reduction in weight and size of the system provided a more natural environment for ambulatory recording. Direct A/D conversion and storage to MMC remarkably simplified data processing. Improvement in time and amplitude resolution allowed observation during sleep of even fine fluctuations in skin potential and skin conductance, which had been buried in the rolling noise generated by our former analog cassette data recorder.

転動音に及ぼす車輪形状の影響(振動・騒音実験・解析技術,特別オーガナイズドセッション「音色・音質設計技術〜開発者と利用者・第三者を繋ぐ」,振動・騒音改善技術)

It is important to reduce a noise along railway lines not only for high-speed Shinkansen (220-300km/h) but also conventional railways (below 160km/h). The noise of the narrow-gauge lines is composed of rolling noise and traction motor cooling fan noise. This paper describes the effect of wheel shape on rolling noise. We measured the noise by using a one-dimensional horizontal microphone array and did impact testing of Type NA wheel with a doubly curved web. The noise of Type NA wheel with a doubly curved wheel is larger than that of Type A wheel with a curved wheel at about l,250Hz and l,900Hz. The results of wheel characterization measurement by using an impulse hammer show that the rim of Type NA wheel vibrates radially with two nodal diameters with the web vibrating axially at l,250Hz.

Evaluation of wheel dampers on an intercity train

Pass-by noise from high-speed trains is one important area that has to be handled in all new train projects. For the new line between Oslo and the Gardemoen Airport which opened in 1998, very stringent requirements were set out regarding external noise. To reach the target it was decided that the train should be equipped with wheel dampers. Two different types of wheel dampers were used on the train; a ring damper was mounted on the wheels of the driven bogies, whilst plate dampers divided into tuned absorber fins were mounted on the wheels of the trailer bogies. During the type testing of the Airport Express Train, additional measurements were performed in order to evaluate the acoustic effect of the plate wheel dampers. Two test series were performed with the same train set; first with the train in standard configuration and secondly with the wheel dampers removed from the second and third bogie. The external noise was measured at 5 and 25 m distance from the centre of the track at speeds ranging from 80 to 200 km/h. The third-octave filtered time histories were analyzed to calculate the effect of the wheel dampers. As expected, there was a significant reduction of 4–6 dB at frequencies above 2000 Hz, but there was also a reduction of 2 dB for frequencies as low as 800 Hz. This reduction was also found in the parts of the time histories when the rail should be dominating. This implies that the wheel dampers also reduce the rail noise. The total rolling noise reduction for the trailer bogie was 3 dB at 200 km/h and 1 dB at 80 km/h. From comparison with TWINS-calculated sound power levels it was estimated that the wheel noise would be reduced by 5 dB and the rail noise would be reduced by 1 dB at 200 km/h.

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.

The influence of the contact zone on the excitation of wheel/rail noise

Rolling noise is excited by surface roughness at the wheel/rail contact. The contact patch is known to attenuate the excitation at wavelengths that are short in comparison with its length. A distributed point-reacting spring (DPRS) model is used with measured roughness data to determine the contact filter effect, and this result is compared with analytical predictions. It is found that the analytical model gives an attenuation that is too large at short wavelengths but is usable for wavelengths down to somewhat smaller than the length of the contact patch. Additionally, variations in the detailed geometry of the profile can cause the contact point on the wheel and rail to oscillate laterally. This introduces an oscillating moment that can induce additional vibration and noise. The DPRS model and rolling noise prediction model are both extended and used together to allow an estimate of the contribution to the radiated noise. It is found that, while the direct roughness excitation is still more important, the moment excitation can be significant, particularly for conforming profiles.

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.

철도소음의 방사특성에 관한 연구

In order to control the railway noise. we should know the radiation characteristic of the noise during the train passage Generally, the railway noise sources for conventional trains are classified by the rolling noise and power unit noise in tangent track. In this Paper. we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic The calculation results are compared with short distance measurement of three kinds of trains (EMU, Mookungwha, Saemaul). It is shown that the radiation characteristic of the rolling noise that is major noise source of electric multiple unit is dipole type. We know that characteristic of the engine noise is radiated as the cosine type.

철도차량의 전동음 예측에 관한 연구;- 지표면 효과 및 침목에서 방사되는 소음 계산 -

The major noise source for the conventional train is the rolling noise caused by the interaction of the wheels and rails during the train passage on the tangent track. In order to control the rolling noise, the noise radiated from wheels, rails and sleepers should be analyzed and predicted. In this paper, a prediction method of wheel/rail rolling noise generated by the roughness of the wheel/rail surface is described, where the method is considering the effect of noise radiated by sleepers and the effect of ground. The method is applied to the Korean railway system, and the sound pressure level (SPL) predicted by the proposed method is compared with the measured SPL. Overall. the result shows good agreement between the predicted and measured values.

한국형 고속철도에서 방사되는 소음분석

The sources of wayside noise for the high -speed train are the aerodynamic noise, rolling noise and power unit noise. We should know the major source to control noise radiated from train. In this paper, we present the test results on the wayside noise and the vibration of the rail/sleeper during the passing of Korean Train Express (KTX). It turns out that the major noise sources for KTX are the rolling noise and power unit noise at 300 km/h. Generally, the noise attenuation with distance is independent of train speed. However, the test results show that in the near field the noise levels decrease by about 5~6 ㏈(A) per doubling of distance at speed in the range of 50~120 km/h and about 3~4 ㏈(A)/d.d at 300 km/h.

ON THE HORN EFFECT OF A TYRE/ROAD INTERFACE, PART II: ASYMPTOTIC THEORIES

In Part I, it was shown that boundary element method calculations could successfully be applied to determine sound amplification by a tyre/road geometry. However, the computations are expensive, limited to frequencies below 2500 Hz, and provide little physical insight. In Part II, two supplementary asymptotic approaches are developed; a ray theory for high frequencies and a compact body scattering model for low frequencies. When tested on a representative tyre geometry, these methods are found to have excellent predictive capabilities, at frequencies above 3k Hz and below 300 Hz respectively. Furthermore, the ray theory shows that the neglect of curvature in Ronneberger's wedge model (1989 Workshop on Rolling Noise Generation, Institut fur Technische Akustik, Technische Universitat, Berlin) leads to erroneous amplification levels and interference effects, and the scattering model intriguingly predicts that low frequency amplification increases with belt width independently of the tyre diameter. Lastly, this work confirms the importance of numerical calculations for the intermediate frequencies, where tyre noise is most significant.

Controlling noise by wheel and track design

Rolling noise forms the main source of noise from railways. Effective control at source requires a good understanding of the mechanisms of generation. To this end, detailed theoretical models for rolling noise have been developed. Using these methods, it is possible to evaluate the rolling noise behaviour of different wheel and track designs, allowing new designs to be derived that are inherently quieter. In this paper, an overview is given of the mechanisms involved in noise generation and the parameters that have most influence are identified. Examples are then given of two techniques that have been developed using the model with the aim of reducing the noise at source. A tuned absorber system applied to the rail is found in field measurements to reduce the noise from the track by about 6 dB(A). The wheel component of noise can be reduced by an optimised wheel shape in combination with damping treatments.

SOUND RADIATION FROM A VIBRATING RAILWAY WHEEL

The sound radiation characteristics of a railway wheel are investigated by using boundary element calculations. The axisymmetry of the wheel allows an axi-harmonic formulation to be used, in which the wheel is defined by a two-dimensional mesh of its cross-section and the motion is decomposed into harmonics of different numbers of nodal diameters. The radiation ratios of the wheel, vibrating in its various normal modes, are calculated for a range of frequencies. The effects of variation in the wheel radius, web thickness and tyre depth are also investigated. From these results, simple formulae are proposed that allow the radiation ratios to be approximated closely. These are more convenient than the boundary element calculations for calculating the rolling noise from a wheel since they are a function of a few simple geometrical parameters. The directivity of wheel radiation is also considered, with comparisons with measured data indicating that simple monopole and dipole characteristics can be applied.

A HYBRID MODEL FOR THE NOISE GENERATION DUE TO RAILWAY WHEEL FLATS

A numerical model is developed to predict the wheel/rail dynamic interaction occurring due to excitation by wheel flats. A relative displacement excitation is introduced between the wheel and rail that differs from the geometric form of the wheel flat due to the finite curvature of the wheel. To allow for the non-linearity of the contact spring and the possibility of loss of contact between the wheel and the rail, a time-domain model is used to calculate the interaction force. This includes simplified dynamic models of the wheel and the track. In order to predict the consequent noise radiation, the wheel/rail interaction force is transformed into the frequency domain and then converted back to an equivalent roughness spectrum. This spectrum is used as the input to a linear, frequency-domain model of wheel/rail interaction to predict the noise. The noise level due to wheel flat excitation is found to increase with the train speed V at a rate of about 20 log0V whereas rolling noise due to roughness excitation generally increases at about 30 log0V. For all speeds up to at least 200 km/h the noise from typical flats exceeds that due to normal levels of roughness. When the wheel load is doubled the predicted impact noise increases by about 3 dB.

Two-dimensional finite element simulation of the thermal problem at railway block braking

Rolling noise levels from railways are strongly dependent on the roughness generated on the running surfaces of wheels and rails. As an initial effort concerning the wheels, a two-dimensional finite element (FE) model of the transient thermal convection-diffusion problem at block braking is developed. The streamline diffusion method is used to stabilize the solution. A constitutive law is adopted that describes the division of frictional heat between block and wheel. The model parameters are calibrated using available experimental data, and a sensitivity analysis is carried out. The results are in good agreement with experimentally obtained experience, especially regarding the division of frictional heat.

Geometric Descriptors of Road Surface Texture in Relation to Tire-Road Noise

The paper deals with the determination of geometric parameters for studying the relationship between tire-road noise and texture of road surfaces. The approach was found to be an alternative to classical spectral analyses and numerical simulations of the tire-road contact. Texture parameters were derived from previous works at the Laboratoire Central des Fonts et Chaussées related to the influence of the microtexture of road surfaces on skid resistance. Use of these parameters was justified by consideration of generation mechanisms of rolling noise. Texture, rolling noise, and absorption measurements were performed on 12 road surfaces. The measuring devices and the test methods produced texture profile analyses, including the spectral and geometric approaches. Geometric parameters were defined. Correlation between the noise and texture spectra showed results similar to those published in previous works. Fair tendencies were found between the global noise level at 90 km/h and the geometric parameters. Unexpected results obtained on the porous asphalt surfaces were partially explained by the attenuation effect, which was quantified by means of existing models. Results from the correlation between the third-octave-band noise levels and the geometric parameters corroborated those of the spectral analyses.

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.