What is acoustic pollution and what causes it?

• If the variation of sound pressure in a particular area is about 10-100 Pa, we say that the area is acoustically polluted.

• Acoustic pollution is present: on the streets due to the vibration of road surfaces caused by the passage of transport vehicles; near construction or manufacturing areas; wherever "noisy" devices are being used. Nowadays, there are numerous sound sources that cause acoustic pollution, which affects the quality of life and health of 25% of the European population.

Regulations

• In 1993, in its "Fifth Environmental Action Programme", the European Commission stated that noise is a serious environmental problem and - in the following "Sixth Environmental Action Programme", which was valid for the decade of 2001-2010 - a regulation was changed to help control the problem. It called for using "sound maps" (acoustic zoning) during urban planning and setting new limits on noise produced by all machines. These measures would reduce the total population exposed to acoustic pollution by 15% with respect to the year 2000.

• The action plan called for alternatives to current pollution situations and, above all, was a serious attempt to make the population aware of the problem and responsible for contributing positively to a solution.

• In Italy, the region of Lombardy has the most cities that have conducted acoustic zoning.

• To carry out acoustic bonification, there is a need for both local technical competences and the political will to implement Bonification Plans.

• The Italian DPCM 14/11/97 (Prime Minister's Decree 14 November 1997) sets the maximum limit of exposure to noise in both internal and external environments. Various types of areas were identified:

type of area	maximum dB daytime	maximum dB nighttime
exclusively industrial	70	70
primarily industrial	70	60
intense commercial activity, high population density, railway lines, ports, etc.	65	65
mix of average population density and average industrial/rural activity	60	50
residential	55	45
protected (hospitals, schools, recreational buildings)	50	40

What can be done?

• To deal with acoustic pollution, the first thing needed is legislative interventions that set parameters to be respected regarding the construction of new buildings and the improvement of existing ones.

• A good example is building road surfaces with porous, phono-absorbent material or, even better, constructing main thoroughfares that move heavy traffic away from city centres. Another two highly effective interventions are creating bicycle paths and insulating closed environments where sounds are produced with phono-absorbent material.

• Acoustic pollution near railway lines is caused by friction between the train wheels and the train tracks, as well as traction and braking systems. High-speed trains cause even more noise due to friction between the trains and the air.

• Currently, many interventions are being implemented to solve these problems, such as improvement of braking systems and track welding techniques. With regards to the aerodynamic noise, new solutions are being sought, particularly considering that many more high-speed trains will be used in the future.

• Acoustic pollution caused by air traffic is being dealt with through preventive strategies that call for the replacement of obsolete, noisy airplanes, the limiting of night flights and the use of noise maps, especially near airports during take-offs and landings.

To preserve your hearing

Many measures can be adopted to preserve one's hearing. A good example is to try using personal music players without putting the volume at maximum level. This will avoid producing a high concentration of waves against the eardrum and reaching sound pressure levels close to the pain threshold.

Sound pressure levels in discotheques often reach levels that go beyond the pain threshold and frequent exposure of eardrums to this situation at a young age can cause hearing loss.

In-depth study and links

• For a scale of audible intensity, see the page on Sound pressure levels
• Tables of useful dB values and various units of measurements for sound pressure can be found on these pages regarding Useful dB values and Pressure and its units of measurement.
• For further study, see the pages on Perception of loudness and Architectural acoustics.

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