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Ljud från vindkraftverk

The same configuration settings as for Nordic Prediction Method for industrial noise apply.

Please refer to Nordic Prediction Method (1996).

Additional Information

Propagation Model

The guideline states different equations for the geometrical divergence over land and over water.

Propagation over land

For distances r <= 1000 m:

\(L_{p,A} = L_{WA,korr}-8-20 \lg r - 0.005r\)

with

  • LWA,korr: A-weighted sound power level, corrected for terrain roughness and statistical error (see below)
  • r: distance source-receiver (m)

For distances r > 1000 m:

\(L_{p,A}=L_{WA,korr}-10-20 \lg r - \Delta L_a\)

with

  • LWA,korr: A-weighted sound power level, corrected for terrain roughness and statistical error (see below)
  • r: distance source-receiver (m)
  • ΔLa: correction calculated according to:

\(\Delta L_a = 10 \lg \sum 10^{(L_i+A_i)/10}-10 \lg \sum 10^{(L_i+A_i-r*a_i)/10}\)

with:

  • Li: A-weighted sound pressure level (background level) at the receiver
  • Ai: A-weighting for octave data, 63 to 4000 Hz (dB)
  • ai: air absorption (dB/m)

Propagation over water:

\(L_{p,A}=L_{WA,korr}-8-20 \lg r - \Delta L_a +10 \lg(\frac{r}{200})\)

Note

The correction term ΔLa is not evaluated by CadnaA and, thus, has to be accounted for after calculation.

Terrain Roughness

The correction for terrain roughness Δvh (based on the roughness length z0) is not considered by CadnaA as this is part of the emission data. This correction will have to be calculated externally and to be added to the sound power level PWL.

Statistical Error

The statistical error k is also considered to be part of the emission (see also example on page 25 of Lfv-2001). Again, this correction will have to be calculated externally and to be added to the sound power level PWL.

Ground Absorption

The object „Ground Absorption Area“ (see Ground Absorption Areas) can be applied in conjunction with the tab „Ground Absorption“ (see Ground Absorption Tab) with "Ljud från vindkraftverk". There are two cases to be distinguished by the ground factor G:

  • propagation over land (soft ground): G > 0.5
  • propagation over water (hard ground): G <= 0.5