# Railway noise Gijsjan van Blokland M+P Ard Kuijpers M+P sources:

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

topics Relevance Sources Model of generation process of 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

Dose-effect relation for three transport noise sources

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

Speed relation for the three noise sources

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

Sound emission of train types

Bronnen en snelheid (II)
aerodynamisch rolgeluid geluidniveau rolgeluid bij afscherming >350 km/h snelheid

Rolling noise

Effect of braking system on wheel roughness and sound production
Wavelength translated to frequency: f=v/λ 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

level of rail roughness
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

Rail corrugation, wavelength of 4 cm clearly visible

Combined wheel/rail roughness (dB re 1 m)

Modeling rolling noise (1): force generation

Modeling rolling noise (2): force  sound radiation

Contribution to rolling noise

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

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

Radiation efficiency σ: log of ratio of sound/vibration

Vibration of track system

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

Track vibration: effect of pad stiffnes

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

Dependence of rolling noise on pad stiffness

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

Contribution to rolling noise (again)

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

Model of rolling noise (Twins)

Reducing rolling noise

Effect of braking system on roughness and noise

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

Effect of rail grinding after some years

Effect of wheel shape

Effect of types of wheel damping

Effect of wheel geometry

types of rail dampers

ISVR/CORUS damper

Effect of damper

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

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

Results Metarail Project
Influence on Noise

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. Rotterdam Köln Basel Milano Bettembourg Lyon 1177 km 490 km Total line length: 1667 km

Instruments for strategic noise abatement Cost-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

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

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

Case: HSL-Zuid

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

Effects of slab track

Noise increase due to higher rail contribution
TWINS: verschil ballast – 240 km/h: Hz ballast track Slab track (Rheda) total wheel rail/ baseplate Sleeper/ slab

Noise difference ballast – slab track as a function of frequency
125 250 500 1000 2000 4000 8000 -10 -5 5 10 15 20 frequentie [Hz] L p,UIC 54 beton kaal - L p,UIC 54 ballast [dB(A)] Goederen (Best) ICR (Best) Goederen (Deurne) ICR (Deurne) Effect centered around 800 Hz, rail contribution

optimal dynamic properties
Noise improved design Higher rail damping Tighter connection with sleeper Damped fixation of sleeper in slab Cork-rubber with optimal dynamic properties

Noise improved design, adding of absorption
German slab track construction

Curve squeal

Curving behavior

Creep force

Reducing squeal noise

Some general points

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