Ce type d'élément permet de modéliser l'influence acoustique d'une surface de forêt avec une hauteur . Différents coefficients d'atténuation [dB/m] spécifiques peuvent être introduits en fonction de la densité de la forêt.
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Notes:
Le type de sol assigné aux forêts est invariable et toujours absorbant (herbe). Voir aussi Type de sol.
Wenn spektrale informationen einer Quelle vorhanden sind, wird die Hindernisdämpfung durch den Wald spektral berechnet.
For ISO9613-calculations, the "simple" method is based on the original ISO9613:1996 method (which is also presented as the "simplified method" in ISO9613:2024, A.2.2) . [The here implemented extension allows for the specification of the attenuation coefficient at 500Hz; a value of 0.05dB/m leads to the attenuation specified in the original method (which is intended to model a dense forest).] For spectral sources, the provided coefficient is used for 500Hz.
The "detailed" method [≥SLIP'25] is introduced in the 2nd edition of the ISO9613 standard, section A.2.3 [ISO9613:2024]. It uses forestal parameters (stem diameter, basal area, standing stock, horizontal structuring and low-height foliage) to estimate a spectral attenuation coefficient. For nonspectral sources, the attenuation for 500Hz is used.
The ISO9613-standard provides typical parameter values for light, normal and dense forests; these are displayed in the following table.