Modification of ISO9613-2 for long propagation distances

ISO 9613-2 provides a propagation model in which shielding by walls can be predicted. Originally, the ISO 9613-2 was designed to predict sound propagation for industrial noise. The typical propagation distance for industrial noise is usually a few hundred meters at most; for some noise types as shooting noise, much larger distances are often relevant. Due to the great acceptance of the ISO 9613-2, the foliage attenuation of the ISO 9613-2 is also used to predict the attenuation of forest stands. However, it turned out that the foliage model of ISO 9613-2 underestimates attenuation values at larger propagation distances. Therefore, it was investigated how the foliage attenuation can be corrected by means of physically based approaches. In addition, we investigate, if the diffraction method of the ISO 9613-2 also needs to be corrected for longer propagation distances.