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07.01 Railroad & Ground-Borne Noise, Part 2

Development of a dynamic model of the axisymmetric railway wheel for sound radiation prediction
Time: 7:40 am

Author: Víctor Andrés

Abstract ID: 2385

In this work, a vibroacoustic model is developed to predict the dynamic response and sound radiation of an axisymmetric railway wheel under a non-axisymmetric excitation. To do this, first, the energy equation of the wheel is analytically integrated along the circumferential direction after an expansion of its response as Fourier series. Then, the vibrational dynamics of the three-dimensional wheel is solved through a set of two-dimensional problems which come from that integration. Subsequently, the three-dimensional sound radiation of the railway wheel is calculated from the solution of the aforementioned two-dimensional problems by means of analytical relations based on the harmonic distribution of the dynamics in the circumferential coordinate. Additionally, the wheel rotation is introduced in the model using an eulerian approach, in order to consider the associated gyroscopic and inertial effects. The proposed model presents a greater computational efficiency compared to full three-dimensional methodologies, without compromising the precision of the results. This allows the implementation of the sound radiation calculation in optimization algorithms with the aim of achieving quieter designs of railway wheels.

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TMD Tunable for Railway Groundborne Noise Control
Time: 6:00 am

Author: Wilson Ho

Abstract ID: 3136

Tuned mass rail dampers are cost effective for the mitigation of the airborne noise and vibration with the ability to be tuned for individual site. TMDs have been developed and installed at a single rail in a curve tunnel and achieve more than 4dB(A) noise reduction in many cases. According to the on-site noise reduction performance during damper installation, half, one, two or three dampers can be installed at each spacing between two baseplates. TMDs with only half-installation provides more than 10dB reduction at vertical pin-pin resonance (~1kHz). With the standard installation, they provide the strong damping to half the corrugation growth rate. The stick-slip phenomena which causes the corrugation will be affected by the damping effect from TMDs. On the other hand, they can also be tuned to the low-frequency (p2 resonance) for grandborne noise control. The high reduction of the grand borne noise proved our claim for effectiveness of the TMDs besides many other studies on the other parameters like the type of the baseplates or the soil types. According to the test results TMDs achieve strong performance in different range of the frequencies.

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Vibration source properties of cargo trains: free field vibration and trackside measurement analysis
Time: 7:20 am

Author: Eliam Vlijm

Abstract ID: 2785

Annoyance caused by railway operations has gained increasing attention in the Netherlands. This has led to a multimillion research project into different aspects of train passages as a source of vibration. The project is initiated by the Dutch railway operator ProRail. In advance of this project a study has been performed on vibration signals at free field caused by cargo train passages at four different sites. The signals have been compared to trackside measurements. The trackside measurements consist of fibre optic measurements of the rail deflection at pre-installed locations different from the free field vibration measurement sites. Different vibration level indicators have been studied like train speed, axle loads and wheel roughness indicators and their correlation with vibration levels. Vibration levels are defined in several ways, a frequency weighted running mean square value (so-called Veffmax), a 2-second RMS level (unweighted) and levels per frequency band. Special attention is given to the variation in time of the measured vibration signals during the train passage to see whether ‘bad quality’ wheel passages can be identified. The results give valuable input for a future case study in which wheel quality and its influence on vibration levels will be studied further.

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Time: 6:20 am

Author: Akif Yavuz

Abstract ID: 2834

Many academics have examined the disc brake squeal problem with experimental, analytical, and computational techniques, but there is as yet no method to completely understand disc brake squeal. This problem is not fully understood because a nonlinear problem. A mathematical model was created to understand the relationship between brake disc and pad thought to cause the squeal phenomenon. For this study, two degree of freedom model is adopted where the disc and the pad are modeled. The model represents pad and disc as single degree of freedom systems that are connected together through a sliding friction interface. This friction interface is defined by the dynamic friction model. Using this model, linear and nonlinear analyzes were performed. The stability of the system under varying parameters was examined with the linear analysis. Nonlinear analysis was performed to provide more detailed information about the nonlinear behavior of the system. This analysis can provide information on the size of a limit cycle in phase space and hence whether a particular instability is a problem. The results indicate that with the decrease in the ratio of disc to pad stiffness and disc to pad mass, the system is more unstable and squeal noise may occur.

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The effect of two trains passing at the same time on the ground borne vibration level
Time: 6:40 am

Author: Carel Ostendorf

Abstract ID: 2853

When predicting the ground borne vibration level, it is assumed that only one train passes so the predicted vibration level is caused by a single train. When there is one track for every direction of the train, it is possible that two trains will pass each other on a specific location at the same time. What influence do these two trains have on the vibration level compared to the vibration level of a single train passing that same location? For this study ground borne vibration levels have been measured on two locations in The Netherlands using a 3 by 3 grid, 25 meters apart, on a distance of 25, 50 and 75 meters of the track. During the 4 weeks measuring time, all the trains have been captured on video. All the double train situations have been marked. The corresponding vibration level Vmax (according to the Dutch SBR B guideline) has been determined for both the single trains and the double trains and compared to each other. In the analysis, the type of trains passing each other and the distance of the receiver to the track, has been taken into account when determining the difference in vibration level.

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Methods for the assessment of low-frequency noise from mining activities in the Netherlands
Time: 7:00 am

Author: Jelle Assink

Abstract ID: 3000

According to the World Health Organisation, noise ranks among the environmental stressors with the highest impact on public health. The contribution of low-frequency noise (LFN) is not well-understood and deserves more research attention from several perspectives, that include epidemiology, acoustics as well as civil engineering. The attribution of symptoms to LFN is increasing due to a growth in public awareness and the expansion of industrial installations and traffic. In the Netherlands, numbers of LFN-related complaints are rising. Several of those have been attributed to the mining industry. However, an effective methodology for the assessment of such complaints is not yet available. In this presentation, methods are defined to assess LFN from mining activities in the Netherlands, focusing on the extraction, processing, transportation and storage of gas, salt and geothermal heat. Through a literature review and interviews with domain experts, methodologies have been derived with regards to 1) the prediction of LFN generation at the source, 2) observational techniques and 3) potential impacts on health. A broad low-frequency band is considered, spanning from the often-discarded infrasonic frequencies to up to 200 Hz. Based on this study’s results, recommendations are given for establishing a standard procedure to assess LFN produced by mining activities.

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