Train noise

Train noise is vehicle noise created by trains. Noises may be heard inside the train and outside.

Subway systems, light rail transit and freight trains can send loud train noise into neighborhoods. Organizations such as the World Health Organization and the U.S. Environmental Protection Agency have set guidelines for noise level decibel limits for rapid transit. Noise levels can be reduced by installing noise barriers next to the track.

Sources

Several distinct sounds are created by various parts of the train, such as engines, traction motors, brakes, and the wheels turning on the rails.

  • Roughness and irregularities on the wheel and rail surfaces are a source of noise and vibration. Rail joints and squats on the rail cause a familiar "clickety-clack" sound as train wheels roll over them. Rail corrugation (a periodic wear pattern resembling corrugated materials) causes tonal noise and vibration; fine, short-wavelength corrugation is known as "roaring rails" due to its high-pitched sound, whereas coarse, long-wavelength corrugation can cause the ground and nearby buildings to vibrate.[1]
  • Rail squeal is a sound caused by a train's wheels slipping under specific conditions, usually in sharp curves.
  • Air displacement of a train in a tunnel can create noise from turbulence.
  • Trains also employ horns, whistles, bells, and other noisemaking devices for both communication and warning.
  • The engines in diesel locomotives and DMUs produce significant amounts of noise. Newer locomotives have become much quieter in recent years due to Federally-mandated noise regulations. However, there are still times that a locomotive may develop a defect in its turbocharger, which produces a whine that can be heard for many miles. While this is rare, and usually the said locomotive gets put into the shop quickly, the noise has been compared to an air raid siren, a UFO, or just a very large leaf blower. It appears to be the most common on EMD units equipped with the 710 prime mover, although any turbocharged locomotive may develop this problem.
  • Electric traction motors often produce electromagnetically induced noise. This high-pitch noise depends on the speed and torque level of the machine, as well as the motor type.[2] Variable-frequency drives use pulse-width modulation, which introduces additional current harmonics and results in higher acoustic noise. The switching frequency of the PWM can be asynchronous (independent of speed) or synchronous (proportional to speed), but always results in acoustic noise varying with speed.[3]
  • Noise from wheel axle bearings can be heard especially from mainline trains and changes with speed.

See also

References
  1. Grassie, Stuart L (Nov 2009). "Rail corrugation: characteristics, causes, and treatments". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. 223 (6): 581–596. doi:10.1243/09544097JRRT264.
  2. "J. Le Besnerais et al., Characterization of the audible magnetic noise emitted by traction motors in railway rolling stock", Noise Control Engineering Journal, ISSN 0736-2501, Vol. 57, Nº. 5, 2009, págs. 391-399
  3. J. Le Besnerais, V. Lanfranchi, M. Hecquet and P. Brochet, "Characterization and Reduction of Audible Magnetic Noise Due to PWM Supply in Induction Machines," in IEEE Transactions on Industrial Electronics, vol. 57, no. 4, pp. 1288-1295, April 2010. doi: 10.1109/TIE.2009.2029529


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.