View source for Traffic Noise Overlay

{{learned|what the Traffic Noise overlay is|which information is displayed on the Traffic Noise overlay|how to add or remove the Traffic Noise overlay|}}
==What is the Traffic Noise overlay?==
[[File:Traffic_Noise-Overlay.jpg|thumb|left|Optional Traffic Noise overlay]]
The Traffic Noise Overlay is an [[Grid overlay|overlay]] which displays the impact of traffic noise in DB(A) for the project area. Based on [[Traffic Flow (Overlay)|traffic flow]], distance and several computation parameters a grid is calculated for the project area. Note, this overlay only shows the impact of traffic noise on top of a background value of 48 dB(A). Influence of other sources (e.g. windmills, air traffic, factories, etc) is excluded.
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==Adding and removing==
To add a traffic noise overlay go to the Overlays menu in the GEO DATA ribbon and select Add Traffic Noise. To remove the overlay, press Remove below the overlays list.

[[File:Noice_overlay_01.PNG|700px]] [[File:Noice_overlay_02.PNG|700px]]

==Calculations==
The calculations follow the standard rekenmethode 1 (SRM 1), as described on [http://wetten.overheid.nl/BWBR0031722/2015-07-01#BijlageIII]:

LAeq = E + Co + Cr - Da - Dl - Db - Dm

where:
* LAeq: equivalent noise level (dB(A))
* E: emission
* Co: acceleration term (default = XXX dB(A))
* Cr: reflection term (omitted)
* Da: distance reduction
* Dl: air reduction (default = XXX dB(A))
* Db: surface reduction (default = XXX dB(A))
* Dm: meteorological reduction (default = XXX dB(A))

Default values are taken from InfoMil [https://www.infomil.nl/onderwerpen/geluid/regelgeving/wet-geluidhinder/wegverkeerslawaai/akoestisch-rapport/cwegdek/]

===Emission===
Emission is computed as:

E = 10 * log(10^(Elv/10)+10^(Emv/10)+10^(Ezv/10)

Per vehicle category, the emission is computed as:

Em = am + bm * log(m/v0) + 10 * log(Q/vm)+Cw;m 

and  

Cw;m = σm + τm x log(vm/v0,m)

where:

* m: vehicle category (light weihgt, medium weight and heavy)
* a and b: factors to be found at InfoMil [https://www.infomil.nl/onderwerpen/geluid/regelgeving/wet-geluidhinder/wegverkeerslawaai/akoestisch-rapport/cwegdek/]

* Cw = road surface correction
* σ = correction factor at reference traffic speed
* τ = correction factor per 10 km/hour deviation from reference traffic speed

===Distance reduction===
Distance reduction is computed as:

Da = 10 * log(r)

where:
* Da: distance reduction
* r: shortest distance between the source and point of evaluation

[[File:Geluidsoverlast.png|600px]]

==References==
The overlay calculations are based on Standard Calculation Method 1 (SRM1) as defined by the dutch government: [http://wetten.overheid.nl/BWBR0031722/2015-07-01#BijlageIII wetten.overheid.nl]

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