How to Provide an Efficient Noise Propagation Control’s Infrastructure (ISO 11690-2)

The need for the companies to adopt a solid noise control policy has been widely covered in a recent article.

Regarding the control of the noise during its propagation – from the source to the receiver (generally the worker) – some or all of the following actions need to be considered meticulously, in order to set-up the most appropriate infrastructure within the plant:

  • Use of vent silencers (for valves and tanks), designed to reduce noise level of exhaust piping to the atmosphere for pressurized gaseous fluids.
  • Use of acoustic barriers (single walls), partial enclosures or full enclosure of the entire item of equipment.
  • Use of enclosures for noisy components on a machine.
  • Use of reactive or dissipative mufflers; the former for low frequency noise or small exhausts, the latter for high frequencies or large diameter exhaust outlets.
  • Use of in-line plenum chambers or lined ducts for air handling systems
  • Reverberation control – the addition of sound absorbing material to reverberant spaces to reduce reflected noise fields. Note that care should be taken when deciding upon this form of noise control, as direct sound arriving at the receiver will not be affected. Experience shows that it is extremely unusual to achieve noise reductions in excess of 3 or 4 dB(A) using this form of control which can be exorbitantly expensive when large spaces or factories are involved. In flat rooms the spatial sound distribution is of interest, see ISO 11690-1,-2.
  • Active noise control, which involves reflection, suppression or absorption of the noise radiated by an existing sound source by use of one or more secondary or control sources.

The commitment starts with a detailed analysis in order to ensure proper noise control measures for the facility design process. Three necessary steps in raw are accurately executed:

  • Field assessments Interpretation
  • Risks Mitigation
  • Reduction of noise control’s costs

All the analysis performed on noise and vibration problems are accomplished taking in account of noise control optimization’ costs, risk management from facility noise, complaints and regulatory compliance challenges.

The fully customized solutions realized by Stopson Italiana cover Oil and Gas, Power Generation, Marine and other industriesThe long-time maintenance assessments and long-term monitoring services are adopted to ensure full compliance over time.

Stopson Italiana is one of the Italian leading provider of innovative sound control solutions, noise impact model design and prediction.

In order to expand its staff, Stopson has recently open five new job positions in the following areas: Design Engineering, Project Engineering, Sales Engineer, and Quality Assurance-Control (QA-QC).
See more on Stopson Italiana CAREER Section.

ventilation silencer

Why control of noise is so important in manufacturing

The main principles that affects the engineering process of a soundproofed plant

The noise pollution is considered nowadays a crucial aspect in the selection and construction of manufacturing plants.

Noise is defined as, “the unwanted, unpleasant or disagreeable sound that causes discomfort to all living beings”. One dB is the faintest sound that a human ear can hear. Unless levels are above 85 decibels, noise pollution should not be a problem in the workplace. Federal occupational safety and health mandates state that if the noise produced by heavy machinery or equipment is in excess of these levels, employers must control noise pollution through engineering and administrative controls.

The environmental noise has been doubling every ten years; The Indian Institute of Oto-Rino Laryngology, Chennai reported, in facts, that increasing industrial pollution damages the hearing ability by at least 20%.

Workers in steel industry, who work close to heavy industrial blowers are exposed to 112dB for eight hours suffer from occupational pollution.

Noise is classified as: Industrial Noise, Transport  Noise and Neighbourhood noise. The first one is caused by industry machines, and it entails noise pollution caused by machines from machines in various factories, plants (e.g. Power Generation and Oil & Gas), industries and mills.

The preceding step to the selection and design of control measures, is to identify and carefully evaluate the noise sources. In order to set up the control strategy with the right approach, the following factors need be considered:

  • Type of sound
  • Noise levels and temporal pattern
  • Frequency distribution
  • Noise sources (location, power, directivity)
  • Noise propagation pathways, through air or through structure
  • Room acoustics (reverberation)

Additionally, other crucial factors have to be determined, such number of exposed workers, type of work, amount of time spent to the noise’s exposure etc. Where possible, noise levels should be evaluated at locations occupied by workers’ ears.

The noise control planning is based on a “A-weighted immission” (or noise exposure levels) for which the respect of standard ISO 11690-1 is recommended.

Any noise problem may be described in terms of source, transmission path and a receiver (e.g., a worker); thus a noise control plant needs to take into account the relative combinations of this different factors.

The better phase to project a soundproofing system lies in the original design. In fact, when noise control is included in the first design of a new plant (or factory), advantages both in terms of overall performance and costs’ reduction arise.

When noise cannot be controlled to an acceptable level at the source, attempts has to directed to control it at some point during its propagation path. For this reason, an important part of the process consists to identify noise sources and to sort them in terms of contributions to excessive noise.

When the requirements for noise control have been quantified, and sources ranked, it’s possible to consider various options for implementing the control, determining the cost effectiveness of the various options. Generally speaking, some studies put in evidence that the cost of enclosing a noise source is much greater than modifying the source or process producing the noise.

Stopson Italiana produces fully customized solutions for all type of plants and applications: Boilers, Heat Recovery Steam Generator (HRSG), Turbomachinery, Venting systems, Combustion engines and Industrial equipments.

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