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Railway noise

Railway noise. Gijsjan van Blokland M+P Ard Kuijpers M+P sources: Müller-BBM (D), D. Thompson (GB), M.Dittrich (TNO) . topics. Relevance Sources Rolling noise Propulsion noise Aero dynamic noise Model of generation process of rolling noise Force generation in wheel/rail contact

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Railway noise

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  1. Railway noise Gijsjan van Blokland M+P Ard Kuijpers M+P sources: Müller-BBM (D), D. Thompson (GB), M.Dittrich (TNO)

  2. topics • Relevance • Sources • Rolling noise • Propulsion noise • Aero dynamic noise • Model of generation process of rolling noise • Force generation in wheel/rail contact • Vibrational response of wheel and of rail • Effect of parameter changes in wheel system and rail system • Mitigation measures • Special constructions • Curve squeal • Generation process • Mitigation measures

  3. Dose-effect relation for three transport noise sources

  4. Sources of railway noise (I) Areo-dynamic Propulsion system Rolling wheel/rail system

  5. Speed relation for the three noise sources

  6. Sources of noise at high speed (>300 km/h)

  7. Sound emission of train types

  8. Bronnen en snelheid (II) aerodynamisch rolgeluid geluidniveau rolgeluid bijafscherming >350 km/h snelheid

  9. Rolling noise

  10. Cast iron blocks lead to significant roughness of the wheel rolling surface due to local high temperatures during braking Disc brakes causes no roughness build-up Disc + blocks is the worst combination Replacing cast iron blocks with composite blocks improves noise characteristics Effect of braking system on wheel roughness and sound production Wavelength translated to frequency: f=v/λ

  11. Rail surface is not completely flat, rail roughness increases by use Cause not fully understood Worst situation is periodic irregularity with a 4 cm wavelength f=v/λ: 4 cm at 40 m/s equals 1 kHz level of rail roughness

  12. Rail corrugation, wavelength of 4 cm clearly visible

  13. Combined wheel/rail roughness (dB re 1 m)

  14. Modeling rolling noise (1): force generation

  15. Modeling rolling noise (2): force  sound radiation

  16. Contribution to rolling noise

  17. Wheel/rail force reception: mobility (velocity/force)wheel: modal systemrail: no boundery, regular support by sleepers

  18. Calculated using FEM Showing exaggerated cross-section deformation of each mode Wheel: modes of vibration

  19. Radiation efficiency σ: log of ratio of sound/vibration

  20. Vibration of track system

  21. Rail pad defines coupling between rail and sleeper • high stiffness pad  strong coupling  good energy transfer from (low damped) rail to (high damped) sleepers

  22. Track vibration: effect of pad stiffnes

  23. Rail noise level difference (dB) Increased stiffnes baseplate pad Effect of pad stiffnes on vibration and noise level

  24. Dependence of rolling noise on pad stiffness

  25. Radiation efficiency of rail

  26. Rail cross-section deformations - only relevant at higher frequencies- not relevant for total dB(A) level

  27. Contribution to rolling noise (again)

  28. Speed related wheel and rail contribution total rail Noise level wheel speed

  29. Model of rolling noise (Twins)

  30. Reducing rolling noise

  31. Effect of braking system on roughness and noise

  32. Rail grinding • Reduces rail rougnes • Regular grinding: longer wavelengths • Acoustic grinding: 1mm – 63cm • Acoustic effect: 2-4 dB(A) • Effect depending on wheel rougness

  33. Effect of rail grinding after some years

  34. Effect of wheel shape

  35. Effect of types of wheel damping

  36. Effect of wheel geometry

  37. Effect of pad stiffness

  38. types of rail dampers

  39. ISVR/CORUS damper

  40. Effect of damper

  41. Skirts (vehicle mounted barriers) • Only effective in combination with track mounted barriers

  42. Mini barriers • mecahnism: • Mainly sheilding of rail radiation • Added absorption is essential (to prevent multiple reflections) • effect: 5 dB(A) for rail contribution

  43. Results Metarail Project Influence on Noise

  44. Rotterdam Köln 490 km Bettembourg 1177 km Basel Lyon Milano Total line length: 1667 km Cost-benefit study of mitigation measures Calculate costs & benefits for different noise control strategies. Strategies consist of combinations of noise control measures. Two major freight freeways chosen for study.

  45. Instruments for strategic noise abatementCost-Benefit Analysis max. 4 m barriers track system improvement max. 2 m barriers Scenarios of Noise reduction due to rolling stock improvement - 10 dB - 5 dB none rolling stock improvement only

  46. Non-standard rail construction (slab track) Preferred construction for high speed lines in Germany and Netherlands Stable system , even at soft soil Low maintenance High initial costs

  47. Types of track construction • Elasticity in track system is essential to prevent cracks in rail Conventional ballast track Flexible mounted sleepers in concrete slab Rigid mounted sleeper in concrete slab Rail directly mounted in slab

  48. Case: HSL-Zuid

  49. Slab tracks are more noisy then conventional ballast tracks. Why? • Less tight rail to sleeper connection  less damping • No acoustic absorption from ballast • Total effect +2 tot +5 dB(A

  50. Effects of slab track

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