The prevention of noise pollution is necessary so as not to be in breach of noise regulations, in particular for Classified Facilities for the Protection of the Environment (CFPE).
In France, it is notably based on the concept of emergence.

This is the difference between the A-weighted equivalent continuous pressure levels of ambient noise (facility in operation) and residual noise (in the absence of noise generated by the facility, but measured over the period of operation of the facility), which is limited, close to the industrial facility: the dwellings, the building areas and the areas occupied by third parties (including other establishments, industrial or not) constitute the Zones with Regulated Emergences (ZER).

A distinction is made according to the level of ambient noise (including noise from the facility):

  • when it is greater than 35 dB (A), without however exceeding 45 dB (A) the admissible emergence is 6 dB (A) during the day and 4 dB (A) during the night
  • when it is greater than 45 dB (A), the admissible emergence is 5 dB (A) during the day and 3 dB (A) during the night.

In addition, it also brings into play the concept of marked tone.

It is the difference between the sound pressure level in a given 1/3 octave frequency band and the adjacent frequency bands, when exceeding 10 dB in the frequency range 50 Hz-315 Hz or 5 dB in the 400 Hz-8000 Hz frequency range.

From the use of these two concepts arise the limitations of noise emissions which combine with those resulting from a prefectural decree (sometimes: ministerial) fixing the noise levels not to be exceeded at the property limit e.g. 70 dB (A) in during the day and 60 dB (A) during the night.

It should be noted that in the above, the diurnal period extends from 07:00 to 22:00 except Sundays and holidays, while the night period extends from 22:00 to 07:00 as well as Sundays and holidays.

However, production or processing sites, industrial or not, have many sources of noise, which, due to their location, their directivity, and the positioning – with respect to them - of palces where maximum noise levels are imposed are likely to create noise pollution.

Without the following list being exhaustive, and without any particular hierarchy, the following hardware and facilities require sustained attention, since it is a question of avoiding discomfort to the neighborhood, due to noise:

  • ventilation openings (natural or forced) and air inlets through which noise is transmitted, e.g. that of noisy equipment in technical rooms and engine rooms, to which is added the noise of ventilation insufflators or extractors, that of dust removal installations and painting booths, that of the openings of Heating Ventilation Air Conditioning (HVAC) facilities
  • industrial chimneys, because the transported fluid (e.g. more or less pure air, combustion gas) allows the propagation of noise emitted by organs (e.g. fans, motors, turbines) located upstream of the air circuit (of which they constitute the downstream end)
  • decompression vents, the venting of industrial gases (e.g. steam, pure oxygen, nitrogen) being accompanied by significant sound production, the noise thus created adding to that of noisy organs (e.g. control valves), which propagates inside the pressurized fluid network
  • hardware located outside buildings: fans, compressors, motors e.g. electric, pumps, air condensers, refrigeration equipment
  • the hardware (a fortiori if they are particularly noisy by nature: presses, machines for the production or transformation of corrugated cardboard, printing presses, generators, turbines, industrial boilers) located inside buildings if the partitions (walls , roofs) of the latter do not have sufficient acoustic performance in terms of limitation of sound transmissions

Therefore, the prevention of noise pollution requires the design and construction of soundproofing equipment:

  • silencers of all kinds, for fluids at temperature and pressure being ambient, or not
  • canopies, sound enclosures, buildings with high acoustic performance
  • noise barriers

Their definition, sizing and implementation often have to take into account different objectives other than acoustic performance, sometimes involving many related functions:

  • accounting with the proper functioning of the hardware they equip (e.g. in relation to the total pressure loss for silencers, to the dismantling for the enclosures)
  • resistance to climatic and seismic conditions, durability (for all soundproofing devices)
  • other variable technical constraints e.g. compactness, limitation of overweight

The prevention of noise pollution is at the heart of ITS activity (measurements, studies, marketing of soundproofing equipment) in all branches of industry.