Treatment of factory noise nuisance

Regardless of the sector of activity, the treatment of factory noise pollution often addresses two major concerns for manufacturers, in relation to noise regulations:

• employees porotection, for what European Directive 2003/10/EC concerning the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise) is a reference document, fixing:
  • limit exposure values for workers to noise: exposure level L EX,8h = 87 dB (A) and peak sound pressure pcrête = 200 Pa or 140 dB (C) ref. 20 μPa
  • lower exposure values for workers to noise triggering action: exposure level L EX,8h = 80 dB (A) and peak sound pressure pcrête = 112 Pa or 135 dB (C) ref. 20 μPa
  • higher exposure values for workers to noise triggering action: exposure level L EX,8h = 85 dB (A) and peak sound pressure pcrête = 140 Pa or 137 dB (C) ref. 20 μPa
• the preservation of the environment, with regard to which French regulations, if applied, distinguish between the daytime period (7:00 a.m. to 10:00 p.m. except Sundays and public holidays) and the nighttime period (10:00 p.m. to 7:00 a.m. as well as Sundays and public holidays):
  • in some cases, a prefectural decree (when it is not ministerial) sets the noise levels not to be exceeded at the property boundary: this is particularly the case for Facilities Classified for the Protection of the Environment (FCPE) e.g. 70 dB(A) during the day and 60 dB(A) at night
  • emergence i.e. the difference between the equivalent continuous A-weighted pressure levels of ambient noise (industrial site in operation) and residual noise (in the absence of industrial site noise, but measured over the period of operation of the industrial site) is limited in the Regulated Emergence Zones (REZ), which generally include, near the technical facility: homes, building zones and areas occupied by third parties e.g. Public Access Buildings (PAB), other industrial establishments. If the ambient noise level in the REZ (including the industrial site noise) is between 35 dB(A) and 45 dB(A) then the admissible emergence is 6 dB(A) during the day and 4 dB(A) at night. If the ambient noise level in the REZ (including industrial site noise) is greater than 45 dB(A) then the admissible emergence is 5 dB(A) during the day and 3 dB(A) during the night.
  • in the case of a Facility Classified for the Protection of the Environment (FCPE), the marked tone, the presence of which is linked to the difference between the sound pressure level in a given 1/3 octave frequency band and the adjacent frequency bands, is considered undesirable if it exceeds 10 dB in the frequency range 50 Hz-315 Hz or 5 dB in the frequency range 400 Hz-8000 Hz

ITS was involved in the treatment of factory noise nuisance in Eastern Europe. In the electricity production sector, the project involved soundproofing a large-capacity gas turbine (class 9, with a power output exceeding 700 MW); its acoustic power level, around 150 dB(A), was likely to cause irreversible hearing problems at short distances (where personnel assigned to the supervision and maintenance of the industrial site may be located), and very significant noise disturbance well beyond the industrial property boundary (impacting local residents).

Design and construction of equipment for the treatment of factory noise nuisance

ITS markets all types of equipment for the treatment of noise pollution in factories:

• silencers for air and pressurized fluid networks
• noise barriers (acoustic screens)
• soundproof enclosures (canopies) and buildings

For the design and construction of equipment for the treatment of factory noise nuisance in question, the noise reduction principle mentioned last in the list above was adopted, with a metal frame and:

• for fixed or easily removable parts, by elements: industrial soundproofing panels with an absorbing face (modular)
• for acces: (rotating) acoustic doorsets with, for translucent parts (with glazing guaranteeing residual safety in the event of accidental breakage): acoustic window sets

In addition, the ventilation air inlets and outlets (the latter: with fans of which noise must be also attenuated) have been equipped with ventilation silencers (to prevent noise transmission through the openings required for the evacuation of heat dissipated by the enclosed materials).

The design of this building, with exceptional sound insulation performance for the treatment of factory noise nuisance, involved:

• material resistance and structural strength calculations: to ensure the necessary stability of the structures under site conditions (rain, snow, wind, and seismic risks), enabling repair/replacement work on enclosed equipment, for which large areas of walls must be dismantled (of course, without the entire structure collapsing like a house of cards)
• predictive acoustic calculations: to size the building's structural elements and quantify noise propagation at various locations of interest, both near the walls for the protection of personnel - a sound pressure level of less than 85 dB(A) at 1 meter is required -and at the industrial property boundary or even beyond to ensure the peace and quiet of neighbors
• aeraulic (aerodynamic) calculations: to study a ventilation system essential for controlling the temperature inside the building
• electrical study: for the installation of fans and sensors

The construction was carried out entirely in-workshop, with the shipment of prefabricated sub-assemblies of the highest quality, resulting from the sourcing of first-choice raw materials and components, the implementation of proven manufacturing and assembly techniques, the involvement of an experienced workforce, and uncompromising quality controls. The installation was completed in record time, with everything done upstream aimed toward this goal, satisfying a particularly demanding client in a context characterized by very significant challenges (technical, organizational, and financial).

This project for treatment of factory noise nuisance was an opportunity for ITS and its business partners to leverage the experience acquired over decades on similar projects to provide noise reduction equipment of a (constant) quality and durability that few can boast.

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Buildings for the treatment of factory noise nuisance in a power plant similar to those covered by this article

In addition to sound enclosures and noise-barrier walls, ITS markets, for the treatment of the noise nuisance of factories (visible in the photo opposite but not delivered as part of the project subject of this article) soundproofed air intake systems for combustion turbines / gas turbines, exhaust silencers for combustion turbines / gas turbines, and also Vent silencers for pressurized gas