Noise and Vibration Report - Transnet

ENVIRO-ACOUSTIC RESEARCHSCOPING NOISE REPORT – TRANSNET: SWAZI RAIL LINK – DAVEL YARD TO NERSTON RSA ROUTE4.2.1.1 Train movementRail traffic is considered as a line source of noise with a continuous area of impact bothsides of and parallel to the railway line. Railway related noise is general acousticallycharacterised by high noise levels of relatively short duration. The wayside noise radiatedinto a community is the function of a number of different factors, namely:• interaction of wheels and rails;• the vehicle or locomotive propulsion system;• type of locomotive and wagons;• braking technology employed on the wagons and locomotives;• railway alignment, in particular the design radius of curves and turns;• auxiliary equipment;• noise radiated from vibrating structures;• train speed;• train length;• aerodynamics (for high speed operations);• locomotive warning devise or horn noise.Train speed is a major influence parameter for noise emission. The noise due to tractionand auxiliary systems (diesel units, electrically driven powertrains, cooling equipment,compressors), if present, tends to be predominant at low speeds, up to around 60 km/h.Wheel-rail rolling noise is dominant up to speeds around 200-300 km/h, after whichaerodynamic noise takes over as dominant factor. The transition speeds from tractionnoise to rolling noise and from rolling noise to aerodynamics noise depend entirely on therelative strength of these sources. The rolling noise, for example, depends strongly onthe surface condition (roughness) of wheels and rails, whereas aerodynamic noisedepends on the streamlining of the vehicle. The relationship with speed is illustrated inFigure 4-1.P a g e | 25