*2.3.7 Foliage attenuation* Afol

ISO 9613-2 [5] states that the foliage of trees and shrubs provides a small amount of attenuation and only if it is sufficiently dense to completely block the view along the propagation path.

According to [5], the attenuation of sound when propagating through a green barrier or dense foliage of thickness *df,* increases with the frequency and with *df*. The attenuation values are detailed in the Standard for *df* values less or equal to 20 m and greater than 200 m. For thicknesses from 20 m to 200 m, it may be obtained by multiplying *df* by a set of coefficients specified for each frequency band.
