Division Sound level in favourable conditions (LF) for a path (S,R)

The term A_F represents the total attenuation along the propagation path in favourable conditions, and is broken down as follows:

where

• A_div is the attenuation due to geometrical divergence;

• A_atm is the attenuation due to atmospheric absorption;

• A_boundary,F is the attenuation due to the boundary of the propagation medium in favourable conditions. It may contain the following terms:

  • A_ground,F which is the attenuation due to the ground in favourable conditions;

  • A_dif,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 A_ground,F is calculated with no diffraction (A_dif,F = 0 dB) and A_boundary,F = A_ground,F ;

• or A_dif,F is calculated. The ground effect is taken into account in the A_dif,F equation itself (A_ground,F = 0 dB). This therefore gives A_boundary,F = A_dif,F .