The poor management of an infrastructure project’s acoustic impact can put paid to the work of years. Ferrovial is aware of the importance of establishing a strict noise mitigation policy and of the need to collaborate with authorities and neighbours on meeting their needs.
Insomnia, stress, cardiovascular or hearing problems are some of the ailments that can be caused by continued exposure to a source of noise. In Ferrovial’s activity we can identify several: machinery employed in its construction projects, vehicles travelling on the roads it manages, aircraft that land and take off in its airports. Noise,
and specifically mitigating it, is a key factor in the design, planning and execution of the company’s projects. Reducing acoustic impact is not just a legal imperative which, in the case of Spain, is defined by certain regulations, both European (Directive 2002/49/EC) and national (Act 37/2003), and by royal decrees 1513/2005 and 1367/2007 that implement it; it is also a question of engaging with the community.
This is well known to Dámaso Alegre, Head of the Acoustic Engineering Department of the Ferrovial Agroman Technical Office. “Poor management of the noise generated by a project can put paid to the work of years”, he declares. Alegre’s is an authorized voice in this field. A glance at his CV is proof of this. In the past 28 years he has participated in more than 100 construction projects, technical reports and acoustic impact studies. He is an expert member of the European Standards Committees for noise reduction devices on roadways and Honorary President and Executive Vice President of the European Noise Barrier Federation.
His team’s task revolves around designing and implementing measures against noise applicable during the construction and operation of an infrastructure. To define these measures they need to calculate the infrastructure’s real acoustic impact, considering aspects such as the strength, intensity and pressure of the sound, distance between the infrastructure and inhabited areas or the existence of natural obstacles, among others. The most common method for graphically representing these data is a noise map, which can be made through simulations (applied to projects pending execution) or real measurements (most often used in infrastructures in operation). However, as Alegre insists, as well as physical factors there is another one to be taken into account, which he calls “discernibility”: the ability of the human brain to recognize a sound in a noisy environment. “Think of a tap dripping in the night. Despite its low sound level, it can prevent us from falling asleep. This example demonstrates that to discover the real acoustic impact of our projects, we need to know and respond to neighbours’ claims”, he says.
MINIMIZING ROAD NOISE
The noise generated by an infrastructure can be dealt with in three ways: by acting on the source of the noise, by acting on sound propagation or by acting on noise receptors. The first alternative would include creating low-sonority surfaces that dampen the noise generated by tires rolling on the roadway. Ditecpesa, the Ferrovial Agroman subsidiary specializing in road surfaces, develops mixes capable of reducing this noise by as much as 3 to 7 decibels. The third one refers to home insulation in the installation of windows and in building more effective façades. The second one is the most common in the projects undertaken by Ferrovial.
It encompasses the installation of obstacles or absorption elements that limit sound propagation, from creating earthen banks with a more limited attenuation capacity through diffraction to installing acoustic screens and partial or total covers, which are far more effective.
Once the measures have been implemented, we provide ongoing technical assistance for the project, monitoring the sound levels generated and the strategic noise maps required by the European Directive
At present the most widely used barriers of this type are acoustic screens. Their design is complex, as it requires taking decisions on several factors that will determine their efficacy such as location size, structure, materials or foundations.
We must also ensure that the screen will not affect the safety of drivers travelling on the road and avoid a strong visual impact on the landscape. All these factors are closely dependant on the lifespan we wish to give the screen. It is advisable to define its characteristics with the service horizon year in mind, when traffic conditions may be different to those registered in the year of installation.
“Our job doesn’t end here. Once the measures have been implemented, we provide ongoing technical assistance for the project, monitoring the sound levels generated and the strategic noise maps required by the European Directive”, explains
Alegre. One of the projects he fondly remembers is that of the acoustic insulation of Puerta de Atocha Station. “The Higher Court of Justice of the Madrid Region had handed down a ruling that required rigorous compliance with the Municipal Byelaw on Noise and Vibration and entrusted us with designing a solution that would meet this legal imperative. We had to introduce technological innovations in the calculation programs and we took in-situ noise measurements of emissions from the station platforms of 140 dBA maintained for 1 minute, one night between 2 and 3 in the morning”. In the 20 years since then, Ferrovial has remained at the forefront of solution for mitigating noise in all its projects
MANAGING ACOUSTIC IMPACT IN AIRPORTS
Another of Ferrovial’s activities in which mitigating acoustic pollution is a priority is airport management. The four airports in which the company has a stake are developing strategies aimed at reducing aircraft noise at take-off and landing. Heathrow Airport has drawn up a specificn action plan that includes initiatives such as acoustically insulating residential buildings and public facilities (schools, hospitals, residences, libraries, etc.), repairing damage caused by noise and collaborating in the relocation of families that are especially exposed to noise. It has recently approved the ‘Quieter Homes’ plan, which will offer different acoustic insulation options, free of charge and tailored to homes. From an operational point of view, Heathrow has resolved on becoming one of the first European airports in dispensing with the oldest and noisiest aircraft. It is also working with NATS to reduce nighttime, noise in order to improve the rest time of adjacent towns, and the airlines operating in its facilities are introducing technologies to mitigate the acoustic pollution of their aircraft.
For its part, Glasgow Airport, will launch a public consultation in January 2018 on its Noise Action Plan which will set out how the airport aims to manage and, where possible, reduce the effects of airport-related noise. The airport is committed to maintaining a fluid and regular dialogue with the local communities it serves in order to understand and respond to their concerns in regard to the noise derived from its activity. Lastly, Southampton and Aberdeen airports have action plans in placethat contemplate monitoring noise levels, introducing preferential routes and timetables and collaborating with airlines so that they employ less noisy and more environmentally-friendly aircraft.