| 1. |
- Liu, Xiaowan, et al.
(författare)
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Measurements and modelling of dynamic stiffness of a railway vehicle primary suspension element and its use in a structure-borne noise transmission model
- 2021
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- The noise inside railway vehicles is transmitted by both structure-borne and airborne paths and, although there are many sources, the rolling noise is often the most important. This paper focuses on the structure-borne transmission of rolling noise in a metro vehicle. Measurements are presented first of the vertical and lateral dynamic stiffness of a primary suspension element consisting of conical rubber/metal elements. Results are presented for various constant preloads over the frequency range 60600 Hz. An analytical model of the suspension element is also developed, based on a mass-spring system and including wave motion within the rubber elements. The dynamic stiffness results are used in a finite element model of the running gear, consisting of the bogie frame, wheelsets and suspension elements. The excitation is provided by the combined wheel/rail roughness at the contact point. This model is used to calculate the blocked forces at the connection points between the secondary suspension elements and the car body. The blocked forces are combined with measured vibro-acoustic transfer functions from these mounting points to the vehicle interior to determine the structure-borne noise inside the vehicle. The proposed methodology is validated against measurements during operation in terms of acceleration levels, blocked forces and structure-borne noise levels inside the vehicle, showing reasonably good agreement. Including the dynamic stiffness for the primary suspension leads to improved agreement between 100 and 500 Hz compared with using a constant stiffness.
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| 2. |
- Thompson, David, et al.
(författare)
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Assessment of measurement-based methods for separating wheel and track contributions to railway rolling noise
- 2018
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Ingår i: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 140, s. 48-62
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Tidskriftsartikel (refereegranskat)abstract
- The noise produced during a train pass-by originates from several different sources such as propulsion noise, noise from auxiliary equipment, aerodynamic noise and rolling noise. The rolling noise is radiated by the wheels and the track and is excited by the wheel and rail unevenness, usually referred to as roughness. The current TSI Noise certification method, which must be satisfied by all new mainline trains in Europe, relies on the use of a reference track to quantify the noise from new vehicles. The reference track is defined by an upper limit of the rail roughness and a lower limit of the track decay rate (TDR). However, since neither the rail roughness nor the track radiation can be completely neglected, the result cannot be taken as representing only the vehicle noise and the measurement does not allow separate identification of the noise radiated by wheel and track. It is even likely that further reductions in the limit values for new rolling stock cannot be achieved on current tracks. There is therefore a need for a method to separate the noise into these two components reliably and cheaply. The purpose of the current study is to assess existing and new methods for rolling noise separation. Field tests have been carried out under controlled conditions, allowing the different methods to be compared. The TWINS model is used with measured vibration data to give reference estimates of the wheel and track noise components. Six different methods are then considered that can be used to estimate the track component. It is found that most of these methods can obtain the track component of noise with acceptable accuracy. However, apart from the TWINS model, the wheel noise component could only be estimated directly using three methods and un- fortunately these did not give satisfactory results in the current tests.
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| 3. |
- Torstensson, Peter, 1981, et al.
(författare)
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Hybrid model for prediction of impact noise generated at railway crossings
- 2016
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Ingår i: Proceedings of the 12h International Workshop on Railway Noise (IWRN12), Terrigal, Australia, September 12-16 (2016). ; , s. 539 - 545
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Konferensbidrag (refereegranskat)abstract
- A hybrid model for the prediction of impact noise at railway crossings is presented. The hybrid model combines the simulation of vertical wheel‒rail contact force in the time domain and the prediction of sound pressure level using a linear frequency-domain model. The time-domain model uses moving Green’s functions for the vehicle and track models (accounting for wheel flexibility and a discretely supported rail with space-variant beam properties) and a non-Hertzian wheel‒rail contact model. The time-domain and frequency-domain models are coupled based on the concept of an equivalent roughness spectrum. The model is demonstrated by investigating the influence of axle load, vehicle speed and wheel profile on generated impact noise levels. A negligible influence on impact noise is observed for axle loads in the interval 15 – 25 tonnes. On the other hand, increasing vehicle speed from 80 km/h to 150 km/h, or comparing a nominal S1002 wheel profile with a severely hollow worn profile, result in substantially higher levels of impact noise; for the given wheel and track conditions the differences are in the order of 10 dB(A).
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| 4. |
- Torstensson, Peter, 1981-, et al.
(författare)
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Wheel–rail impact loads and noise generated at railway crossings : Influence of vehicle speed and crossing dip angle
- 2019
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Ingår i: Journal of Sound and Vibration. - : Academic Press. - 0022-460X .- 1095-8568. ; 456, s. 119-136
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Tidskriftsartikel (refereegranskat)abstract
- Wheel–rail impact loads and noise at railway crossings are calculated by applying a hybrid prediction model. It combines the simulation of non-linear vertical dynamic vehicle‒track interaction in the time domain and the prediction of sound pressure level using a linear frequency-domain model. The two models are coupled based on the concept of an equivalent roughness spectrum. The time-domain model uses moving Green's functions for the linear vehicle and track models, accounting for wheel structural flexibility and a discretely supported rail with spatially-varying beam properties, and a non-Hertzian wheel–rail contact model. Three-dimensional surface geometry of the wheel and crossing is accounted for in the solution of the wheel–rail contact. The hybrid model is compared against field measurements and is demonstrated by investigating the influence of vehicle speed and crossing geometry on the radiated impact noise. Based on simulation results, it is concluded that the impact loads and noise can be mitigated by reducing the effective dip angle at the crossing, which is determined by the vertical trajectory of the wheel when making the transition between wing rail and crossing nose.
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| 5. |
- Zea, Elias, 1989-, et al.
(författare)
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Separation of track contribution to pass-by noise by near-field array techniques
- 2016
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Ingår i: Proceedings of the 22nd International Congress on Acoustics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A technique to separate the track noise contribution is proposed based on identifying and extracting the track signature from the pass-by noise information measured with a microphone array relatively close to the track. Separation of the contributions of the vehicle and the track in the pass-by noise spectra is a challenging task, which is currently addressed by a combination of direct and indirect measurements and model predictions. Due to the uncertainties in the separation of the track contribution, whether a vehicle will comply with regulations during certification tests is still very much track dependent. Therefore, accurate means to identify the track contribution to the pass-by noise are needed. In this paper we propose to make use of the fact that in a wide frequency range the track is a distributed source that radiates plane waves at a given angle with respect to the track. By measuring the sound field close to the track with a microphone array, the wavenumber spectrum of the radiated sound can be determined. For the track contribution this wavenumber spectrum is tonal and therefore sparse. We make use of this property to design filters that extract the track contribution to the total pass-by noise. This is illustrated with simulations and experiments.
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| 6. |
- Zea, Elias, 1989-, et al.
(författare)
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Wavenumber-domain separation of rail contribution to pass-by noise
- 2017
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Ingår i: Journal of Sound and Vibration. - : Elsevier. - 0022-460X .- 1095-8568. ; 409, s. 24-42
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Tidskriftsartikel (refereegranskat)abstract
- In order to counteract the problem of railway noise and its environmental impact, passing trains in Europe must be tested in accordance to a noise legislation that demands the quantification of the noise generated by the vehicle alone. However, for frequencies between about 500 Hz and 1600 Hz, it has been found that a significant part of the measured noise is generated by the rail, which behaves like a distributed source and radiates plane waves as a result of the contact with the train's wheels. Thus the need arises for separating the rail contribution to the pass-by noise in that particular frequency range. To this end, the present paper introduces a wavenumber–domain filtering technique, referred to as wave signature extraction, which requires a line microphone array parallel to the rail, and two accelerometers on the rail in the vertical and lateral direction. The novel contributions of this research are: (i) the introduction and application of wavenumber (or plane–wave) filters to pass-by data measured with a microphone array located in the near-field of the rail, and (ii) the design of such filters without prior information of the structural properties of the rail. The latter is achieved by recording the array pressure, as well as the rail vibrations with the accelerometers, before and after the train pass-by. The performance of the proposed method is investigated with a set of pass-by measurements performed in Germany. The results seem to be promising when compared to reference data from TWINS, and the largest discrepancies occur above 1600 Hz and are attributed to plane waves radiated by the rail that so far have not been accounted for in the design of the filters.
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