noise calculation is the process of calculating the level of noise immission using the metric dB(A). Noise immission is created by noise sources (noise emission) of various types which are propagating noise into the environment. A single source will create a certain level of immission primarily driven by originating sound power level and distance influenced by e.g. absorption and reflection. Several noise sources result in typically higher levels of immission. The method or process of determining the resulting immission level is called noise calculation, its graphical representation is called noise map.
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Noise calculation is done for the following reasons
* to calculate a current situation based on existing physics, mostly when a physical measurement at a location is impractical * to predict the resulting immission levels based on a planned change, e.g. set up of a new machineMostly, noise calculation is part of any such planning process and may become part of the decision process for physical change
Environment engineering differentiates between
* indoor sound propagation, e.g. occupational health considerations * outdoor sound propagation, e.g. city planning considerationsas well as type of noise source, e.g.
* industrial noise * rail or air traffic noise * road noiseEach of before mentioned require different algorithms for noise calculation which have been defined over time in a number of different national or international standards. As an example, outdoor sound propagation is defined in ISO standard 9613 which can be received from the ISO organisation or scientific literature.
Calculation Standards
Following standards for noise calculation have been agreed in the past:
' ISO 9613 parts 1 and 2’ defines the calculation methods for outdoor sound propagation (International)
' VDI2714 and VDI2720 ’ Schallausbreitung und Schallschutz im Freien (outdoor sound propagation, Germany)
' DIN18005 ’ Schallschutz im Städtebau (noise protection in cities, Germany)
' TA Laerm ’ Technische Anleitung zum Schutz gegen Lärm (Germany)
' VDI-Richtlinie 3745 Blatt 1 ’ Beurteilung von Schießgeräuschimmissionen (Germany)
' BS 5228 ’ Code of practice for noise and vibration control on construction and open sites (UK)
' RLS-90 ’ Richtlinien für den Lärmschutz an Straßen (noise protection at roads/traffic, Germany)
' CRTN ’ calculation of road traffic noise (UK)
' Schall03 ’ Schienenlärm (calculation of rail noise, Germany)
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Mathematical Background
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Calculation Tools
There is limited number of calculation tools that have been developed primarily by noise experts and small specialized companies. Those have grown over time becoming more user friendly, covering more application cases and adding service elements to the noise calculation tools. Since the process of noise calculation is complex, both from an input perspective (gathering data, modelling the acoustic elements in the field correctly) and from a pure compute power perspective more recently advanced trends wer arising
* moving the calculation routines into self-contained calculation engines * adapting CAD systems for input of acoustic models * moving into 3D for displaying models or even data capture * moving into cloud services and web enabled calculation tools.Afterall, the quality of results from the noise calculation very much depends on the quality of the acoustic data provided and the capability of the noise calculation engine.o take decisions.
Some of the software packages more used for noise calculation are:
Some online tools used for noise calculations are: