10-11-2012, 05:53 PM
MITIGATION OF METRO RAILWAY NOISEA Case Study
MetroRly.Noise.ppt (Size: 319 KB / Downloads: 30)
INTRODUCTION
Railways have experienced a renaissance since 1980s
Mass Rapid Transit System (MRTS) / Tracked Transit System has obtained wider acceptance as a convenient mode of urban transportation throughout the world
Refers to electric self-propelled trains
Operations can occur Underground, At Grade or on Elevated Structures
Noise radiated from train operations and track structures generally constitute the major noise sources
Airborne noise is radiated from at grade and elevated structures, while ground-borne noise and vibration are of primary concern in underground operations
All rail noise problems have their origin in structural vibrations – Prof. Manfred Heckel
Noise Sources
Four Basic Sources of wayside airborne noise
Wheel / Rail Noise : Due to wheel /rail roughness
Propulsion Equipment: Traction motors, cooling fans for TM, reduction gears etc.
Auxiliary Equipment: Compressors, motor generators, brakes,ventilation systems, other car mounted equipment
Elevated Structure Noise
At low speed(<15 km/h) auxiliary equipment may predominate
At speeds up to approx. 50 km/h, W/R noise predominates
At speeds greater than 50 km/h, the propulsion equipment noise predominates
For light weight steel elevated structures, the structure noise can predominate at all speeds above 15 km/h
THEORETICAL
All rail noise problems have their origin in structural
vibrations - Prof.Manfred Heckel
Typical data for structure-borne sound excited by train
traffic show that the dominant frequency range is
between 40 and 100 Hz where wheel/track resonance lies
Sbs caused by railways either in neighboring buildings
or inside the coaches is mainly low frequency problem
Airborne sound does not affect the LF sound in a coach
Ground vibrations are very small above 200 Hz
Measurements made close to railways show that the origin
vibration is in the vicinity of wheel /rail contact area.