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.
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