Noise reduction of a facility is required in various contexts:

  • when the thresholds triggering the action are reached or exceeded in terms of workers exposure to the risks due to this dangerous physical agent that noise is, which then requires the implementation of provisions in terms of safety and health [1]
  • when the imposed sound level at the property boundary is not respected [2] or when the admissible emergence does not comply with regulations [3] in regulated emergence zones (REZ); this then makes it necessary measures to reduce the noise annoyance for neighbors who are then often complainants (sometimes: also in the legal sense of the term)

In many cases, these two occurrences are simultaneous, and require - for the noise reduction of a facility - the implementation of an action plan, the scope of which can be variable:

  • noise reduction at source
    • creation of envelopes limiting the transmission of sounds; depending on the case (and depending on the dimensions of the constructions) it may be casings of machines, cowlings, buildings ; sometimes with related functionalities crucial for maintaining normal operating and maintenance conditions for facilities (e.g. ergonomics, access methods, treatment of openings, dismantling, evacuation of heat loads, dust collection)
    • implementation of silencers; for facilities including fans (e.g. air renewal and cooling systems, air condensers) and for processes involving an aeraulic circuit (combustion process e.g. furnaces, engines, gas turbines) with a fluid (often: air) at ambient upstream temperature and a very high gas downstream temperature (e.g. for exhaust) or a pressurized fluid network, with decompression vents

In the case of such a noise reduction at source, the sound power level of all or part of the facility is reduced.

  • limitation of sound propagation
    • installation of anti-noise screens or walls, i.e. obstacles for the direct sound waves path between an emission point (the noise source) and a reception point ; they do not modify the acoustic power of the noisy equipment making up the installation, but act to protect specified locations in the environment

ITS participated in a noise reduction project for a power generation facility in Southeast Asia.

Reduction of noise at source (involving soundproof buildings and ventilation silencers), for two gas turbines and limitation of sound propagation by means of acoustic screens (around two generators) were combined, in the form of large-sized metallic constructions, with a special dimensioning to withstand the climatic and seismic hazards of the installation site.

In such a context, a large reduction in sound levels, illustrating the significant noise reduction of the facility, was not the only technical issue of the project, as many other technical challenges had to be met.

As is often the case in such cases, this project to reduce the noise of a facilty involved:

  • a multidisciplinary engineering team, for the necessary consideration of issues of different kinds (e.g. acoustics, aeraulics, construction technologies for large shear panels assemblies) in relation to such a project, requiring complex studies as well as the preparation of very detailed documentation
  • a highly qualified workforce for the fabrication of the various materials making up the soundproofing equipment, with very thorough quality control, up to the challenges of making them available in the form of a ready-to-use kit assembly very far from the place of production, to be fitted by a human resource locally recruited by the end customer, with relating contingencies

A harmonious project progress, from start to finish, was the opportunity to verify - once again - that ITS and its business partners perfectly master the management of projects in relation to the reduction of the noise of facilities.

[1] according to European directive 2003/10/EC, for the daily noise exposure level L EX, 8hours.: 80 dB(A) and 85 dB(A) are the thresholds, respectively lower and upper, triggering the action; 87 dB(A) is the authorized limit value
[2] in France, a limit is set by a prefectural decree e.g. 60 dB(A)
[3] in France difference (using A-weighting) between the noise level of ambient noise (facillity in operation) and the residual noise level (in the absence of noise produced by the facility), is legally limited: depending on the case 5 or 6 dB(A) during the day and 3 or 4 dB(A) during the night

Preservation of acoustic environment end faq