Railways can be a major source of phonic pollution for local communities. For this reason, infrastructure managers have to implement projects dedicated to reducing noise, including both planning and regulation of action plans.
Sound absorbing barriers are the most common solution implemen-ted to minimise the noise level, being installed both on new and existing lines. Generally, they offer a 10 dB reduction of the noise level , depending on the type of barrier and its height or the distance between the source and location. Many times, their performance is limited because of the infrastructure and the height of adjacent residential buildings, their efficiency being improved if the barriers are assembled closer to the source or receiver. Sound absorbing barriers are more cost-effective than the implementation of noise source control measures.
By 2030, noise reduction measures will be naturally integrated into all railway proces-ses, providing practical and sustainable solutions, implemented with the help of a set of technical and innovative instruments.
Therefore, acoustic isolation criteria include special construction materials for the absorption of noise. Sound absorbing barriers is one of the most commonly used methods. The noise level can be reduced if the upper edge of the barrier is assembled between the noise source and the receiver. The higher, the more accentuated the effect and the benefit can appear when the surface of the barrier facing the railways is made of sound absorbing materials helping reduce noise by around 5 dB compared to acoustic reflective barriers. Usually, in order to protect the citizens, the noise level can be reduced by 10 dB if barriers are higher than 2 metres, and in case of higher barriers, the superior efficiency limit is of 15 dB.
The materials used for manufacturing sound absorbing barriers have to have a life expectancy of over 40 years (with minimum maintenance), have to be water-proof and not to release toxic fumes when burnt. Also, these materials have to be fire-resistant.
According to a EU report on sound emissions problems (Railway noise abatement measures addressing the existing fleet), on 21 countries, noise control needs investments of around EUR 76 Billion (costs permitting the installation of 4-m high barriers, compared to other solutions). However, the most efficient solution for reducing noise is the implementation of projects including the application of new braking solutions, wheel solutions, assembly of dumpers and 2-m high barriers. All these protect around 95% of the citizens from a high noise level.
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