The noise generated by railway traffic can be reduced from the infrastructure design phase. A preliminary solution for limiting phonic pollution is the design of the railway route. “When designing the infrastructure, the end route of the line should not present curves under 1000 m, because the smaller the curve radius is, the noisier the railway passenger or freight traffic. At curves with small radii, the noise level is very high and the rolling noise appears due to the centrifugal forces which force the bogie and the noise created by the “locking” tendency of the bogie”, declares Luscalov.
It is very important that, when designing the line, curves would have radii as large as possible. As regards rolling stock, the trains should be equipped with the latest bogie type optimised due to modern braking systems and variable curve entry. These characteristics will obviously help reduce the wear of the track and will expand the infrastructure life cycle.
When a convoy enters a curve with a small radius, we can hear that specific “squeak” caused by the lateral friction of the wheel to the rail. The noise is very loud and can exceed 100dB. The average noise level reaches 70 to 80 dB.
For example, in the case of the underground infrastructure, the noise level due to the presence of curves with very small radii increases by 10 to 20 dB and considered the extreme values determined by the noise levels sent to the traffic environment of underground units, rapid measures have to be implemented to reduce the noise pollution below the maximum limit admitted by European standards which is of 65 dB.
Technical solutions usually refer to two methods for reducing the noise generated by the traffic in curves with small radii related to constructive general solutions and effective solutions for reducing noise level. “Constructive solutions consist in the development of the maximum admitted overextension for all small radius curves in the network, checking the optimal operation of greasers and the continuous improvement of the condition of the wheel-rail contact surface.
As regards the effective solutions for reducing superstructure noise, it is necessary to use more fastening systems, rail pads made of special rubber and acoustic displays at the level of the rails”, added Luscalov.
All these solutions play an important role in increasing track elasticity with immediate effects on protecting the surfaces in contact, reducing their wear and, obviously, reducing the noise generated by the surfaces in contact.
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