# Commission Directive (EU) 2015/996 of 19 May 2015 establishing common noise assessment methods according to Directive 2002/49/EC of the European Parliament and of the Council (Text with EEA relevance), Division: Sound level in favourable conditions (LF) for a path (S,R)

Extent: E+W+S+N.I.

LF = LW,0,dir – AF
(2.5.5)
The term AF represents the total attenuation along the propagation path in favourable conditions, and is broken down as follows:
LF = Adiv + Aatm + Aboundary,F
(2.5.6)
where
Adiv is the attenuation due to geometrical divergence;
Aatm is the attenuation due to atmospheric absorption;
Aboundary,F is the attenuation due to the boundary of the propagation medium in favourable conditions. It may contain the following terms:
Aground,F which is the attenuation due to the ground in favourable conditions;
Adif,F which is the attenuation due to diffraction in favourable conditions.
For a given path and frequency band, the following two scenarios are possible:
either Aground,F is calculated with no diffraction (Adif,F = 0 dB) and Aboundary,F = Aground,F ;
or Adif,F is calculated. The ground effect is taken into account in the Adif,F equation itself (Aground,F = 0 dB). This therefore gives Aboundary,F = Adif,F .

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Source: https://www.legislation.gov.uk/eudr/2015/996/annex/division/ASSESSMENT/division/2/division/2.5/division/2.5.5/division/1 (the official version)
Page: https://openlegislation.uk/eu-directive-2015-996/annex/division-ASSESSMENT/division-2/division-2.5/division-2.5.5/division-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.