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The Battle Against Noise



© A. Rimeymeille/LMA

Dominique Habault, director of the Transport Noise Research Network.

Noise pollution is by no means a recent issue, nor the toxic by-product of industrialization. Regulations to curb noise go as far back as Ancient Rome and have continued through the Middle Ages until today. Yet day and night, whether we're at work, at play, or at home, noise in all its forms still relentlessly invades our lives. One of the most frequent examples given is transportation noise. The more people travel, the greater the areas affected by noise.

The impact of noise pollution is manifold: it affects hearing, performance (attention and concentration), sleep, and health. These effects are all the more dangerous because people subjected to noise are often unaware of its action. The study of noise and its many dimensions is therefore of vital importance for our society.

In order to reduce noise levels emitted by a source, there are two well-known solutions: passive control, which consists in isolating the source with the help of sound-absorbing materials, and active control, where additional sound sources are used to “cancel out” the effects of the so-called primary source. Although both solutions work well, they cannot be applied to every situation.

For most noise problems, the issue is far more complex. The mechanisms at work that can cause noise need to be clearly identified, understood, and modeled. In the battle against noise, computer modeling has an important role to play. It makes it possible to identify the sources of noise, model their behavior, predict the way in which the sound carries, and test solutions to reduce noise. When a new product is designed, whether it be a vehicle, a tool, or a household appliance, simulations like these help find ways of reducing noise in early stages of the manufacturing process, sometimes even before a prototype is made.

There are many areas of research specifically dedicated to fighting noise pollution. One such field of study is the characterization and development of sound-absorbing or damping materials. Another pertains to complex situations like multisource (planes, trains, cars, etc.) and multisensory (noise and light, noise and vibrations, etc.) exposure. This type of research frequently needs to include other aspects associated with noise such as mechanical and safety factors. But above all, they also need to include the human factor–how we perceive noise. Research is underway to clarify the definition of annoyance, a highly subjective notion linked in particular to culture and education, and to determine its characteristics using reliable indicators.

Lastly, the battle against noise involves describing and planning the urban acoustic environment. And Europe has taken a keen interest in the matter: the 2002 European Directive makes it

compulsory to draw up noise maps for large cities and major routes of transportation, whether it be road, rail, or air. The number one priority is to inform and create a public dialogue about this issue, in order to lay out comprehensive urban traffic maps.

CNRS has for many years been playing an active role in the study of such noise-related problems. In particular, it has set up a Transport Noise Research Network1 composed of twenty French teams, whose program is structured around four topics: acoustic and vibratory sources, propagation in built and open environments, perception and effects of noise on humans, and urban soundscapes. The main objective of this network is to improve our scientific and technical understanding in the field of surface transport noise, and to work with industrial partners in the relevant sectors. It is now in the process of building partnerships across Europe.

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