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Noise Modelling

The noise study is an activity dedicated to the analysis, modelling and simulation of an industrial plant. Noise study has the scope to identify and acoustically model these equipment’s – namely sources – and analyse the effects produced by relevant noise sources, on the environment and on plant personnel.

References

EN ISO 11200Guidelines for the use of basic standards for determination of emission sound pressure levels at a works station and at other specified positions
EN ISO 11203Noise emitted by machinery and equipment - determination of emission sound pressure levels at a work station and at other specified positions from the sound power level
BS 4142Method for rating industrial noise affecting mixed residential and industrial areas
ISO 15664Acoustics – Noise control design procedures for open plant
ISO 15665Acoustics – Acoustic insulation for pipes, valves and flanges
ISO 11546-2Determination of sound insulation performance of enclosures - Measurements in situ
ISO 9613-2Attenuation of sound during propagation outdoors - General method of calculation
ISO 9614-1Determination of sound power levels of noise sources using sound intensity Measurement at discrete points
ISO 9614-2Determination of sound power levels of noise sources using sound intensity Measurement by scanning
EEMUA 140Noise procedure specification
EEMUA 142Acoustic Insulation of pipes, valves and flanges

General

The plant Noise study is developed thought the following 5 main steps:

  1. Data collection
  2. Modelling/simulation
  3. Calculation
  4. Result analysis
  5. Document preparation

The following flow-chart identify the main workflow between each phase, providing evidence how Iteration are handled in case of non-compliance.

Noise Study Activity Flowchart

Modelling

The modelling procedure requires studying of the noise emission sources at the following perspective:

  • Acoustical (acoustic emission),
  • Geometrical (dimensions) and
  • Physical (structure, sub-units).

Calculation

Once the simulation scenario has been defined, it is necessary to choose the calculation algorithm to be used (i.e. the set of equations used by the program to evaluate propagation of the acoustic waves). Standard ISO 9613 shall be used when no contractual-legislative requirements define otherwise.

Calculation can be carried out for all the analysis area (i.e. production of noise isopleths maps) or for defined points which usually correspond to sensible receptors.

Result Analysis

The simulation results are compared against the permissible limits defined by national regulatory/ legislative or contractual requirements. The analysis includes verification of the compliance with aforementioned limits and/or, where such limits are not complied with, the definition of the potential mitigation actions.

Document Preparation

The noise study is finalized with the preparation of a noise study report.

The Noise Study should be structured as follows:

  1. Introduction with a brief description of the purpose and objectives of the study
  2. References and abbreviations
  3. The regulatory framework
  4. Characterization - for the study of environmental impact):
    • Pre-existing ambient noise
    • Identification of receptors
  5. Brief description of the model used
  6. Methodology
  7. Description of the results and conclusions
  8. Any mitigation measures;
  9. List of sources considered spectrum including power output and overall sound pressure;
  10. Noise maps, noise studies for non-dedicated to an environmental impact study should have more maps of work areas as well as a map of the area surrounding the plant noise situation

In order to estimate the operational noise level, the internationally recognized noise modelling software "SoundPLAN" version 8.1 has been utilized. The propagation methodology adopted, and the equations used within the SoundPLAN model are based on the ISO 9613 ‘Acoustics – Attenuation of Sound during Propagation Outdoors’ (ISO, 1996)

SoundPLAN has been developed by Braunstein & Berndt GmbH in Germany, and belongs to the class of sophisticated provisional models, based the technique of the Ray Tracing Inverted (from the receivers), that allow to simulate the propagation of the noise in complex source situations and orography.

The model allows calculating the sound levels due to various types of industrial sources and introduces its own algorithms for the calculation of the ground effect, the absorption and the other phenomena involved. The equations used in order to estimate the propagation of the sound waves, in particular for sources of industrial type, are those described in the International Standard ISO 9613.

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