Comparison of acoustic phenomena in the vicinity of two types of steel plate girder bridges

This paper discusses the results of own research of acoustic phenomena in the surrounding of two railway bridges of different type of decks. One of the objects has an open deck with cross girders and stringers, next has an orthotropic deck and track laid on ballast. The biggest threat for the environment is posed by objects with open deck. The extent of increase in noise reaches as much as 20 dB. Objects with ballast may also affect worsening of acoustic climate around the bridge, in particular under the bridge. Reasons for an increase of noise when a train crosses the bridge in general split in-to two groups: - vibrations coming from vehicle wheels, transmitted through rails to a bridge structure make its components vibrate; large surface of structure may act as membranes of a loudspeaker and emit unwanted sounds; - for bridges with open platform the lack of attenuation by the deck (ballast) make the sounds at point-to-point contact of wheels with a rails freely disseminate.