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 6 dB(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 1.10–1.20 m 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. © 2015 Elsevier B.V

High railway rolling noise reduction by combining existing track based solutions

The overall objective of the EU funded Quiet-Track project is to provide step changing track based noise mitigation systems and maintenance schemes for the railway rolling noise. This paper focuses on the combination of existing track based solutions to yield a global performance of at least 6 dB(A). The analysis and validation was carried out considering a track section in the network of Attiko 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 two software tools for noise prediction, WRNOISE and IMMI with experimental determination of the required track and vehicle parameters. The availability of a detailed rolling noise calculation procedure, which includes the modelling of the wheel/rail source intensity and of the noise propagation with 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) allows for detailed designing of measures and of ranking individual measures. A relevant combination of existing solutions was selected in 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) horizontally distributed in the track bed; - Action 2: Implementation of an absorbing noise barrier with a height of 1.10-1.20 m above rail level and close to the track and vehicle; - Action 3: Installation of rail dampers at the selected track. The selected solutions were implemented on-site and the global performance was measured-step by step-for comparison with simulations. A very good agreement was found between simulations and measurements after installation and a global noise attenuation performance of 9 dB(A) was obtained at the considered receiver location.

"Quiet tram track" infrastructure solutions at Athens tramway network for squealing noise attenuation

The "Quiet City Transport" (QCity) project (6th FRAMEWORK PROGRAMME: SUSTAINABLE SURFACE TRANSPORT - EU Project FP6-516420, Contract No TIP4-CT-2005-516420, 2005") aims to develop an integrated technology infrastructure for the efficient control of road and rail ambient noise. Within this project, the development & implementation of a prototype "Quiet tram track" elastically encapsulated in a prefabricated concrete slab, at Voula extension of the Athens Tramway line to Glyfada suburban area was introduced. The prototype's research, design realization & performance evaluation was based on the following actions: (a) an original campaign of monitoring squeal noise levels including 1/3 octave band analysis at a similar curved track in Athens tramway network for various vehicle speeds ("before"), (b) a model analysis of a prototype "Fastener less embedded resilient tram track for squeal noise reduction including the ROLL - SLIP excitation of the wheel & rail and a time domain analysis considering constant crabbing velocity yields wheel and rail vibrations, (c) a laboratory analysis & development of the "elastomer encapsulation material" with specified vertical & horizontal stiffness, (d) the construction of the prefab slab at the worksite and then the transport and installation in situ, & (e) the performance evaluation regarding squeal noise attenuation by performing an extended noise measurements campaign including 1/3 octave band analysis, at the test site by using the same vehicle in similar vehicle speeds conditions & geometrical characteristics of the curve as above ("after"). This prototype aims at the reduction of the squealing noise emitted in closed curves from tram operation. This activity will support European noise policy to eliminate harmful effects of noise exposure and decrease levels of transport noise creation, especially in urban areas, deriving solutions that will ensure compliance with the constraints of legislative limits. Results comparing both "After" & "Before" campaigns, for all reference speeds of 10,20 & 25 Km/h, suggests an important squeal noise diminution for each Leq passage of some 8-12 dB(A) for the distance of 7,5m & microphone height of 1,2m in the interior of each curve (internal direction)

High rolling noise reduction by combining existing track based solutions

The overall objective of the Quiet-Track project is to provide step changing track based noise mitigation systems and maintenance schemes for the railway rolling noise. Work package 4 in particular focuses on the combination of existing track based solutions to yield a global performance of at least 6 dB(A). The validation was carried out considering a track section in the network of Attiko 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 two software tools for noise prediction, WRNOISE and IMMI with experimental determination of the required track and vehicle parameters (e.g. rail and wheel roughness). A relevant combination of existing solutions was selected in 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) horizontally distributed in the track bed, Action 2: Implementation of an absorbing noise barrier with a height of 1.10-1.20 m above rail level and close to the track and vehicle, Action 3: Installation of rail dampers at the selected track. The selected solutions were implemented on site and the global performance was measured-step by step-for comparison with simulations