Division Treatment of receivers located behind each takeoff and landing ground-roll segment

The Δ _SOR function described above mostly captures the pronounced directivity effect of the initial portion of the takeoff roll at locations behind the SOR (because it is the closest to the receivers, with the highest jet velocity to aircraft speed ratio). However, the use of the hence established Δ _SOR is ‘generalised’ to positions behind each individual ground roll segment — both takeoff and landing —, so not only behind the Start-of-Roll point (in the case of takeoff).

The parameters d_S and ψ are calculated relative to the start of each individual ground roll segment.

The event level L_seg for a location behind a given takeoff or landing ground-roll segment is calculated to comply with the formalism of the Δ _SOR function: it is essentially calculated for the reference point located on the side of the start point of the segment, at the same distance d_S as the actual point, and is further adjusted with Δ _SOR to obtain the event level at the actual point.

This means that the different correction terms in the equations below shall use the geometric parameters corresponding to this reference point located on the side of the start point:

where Δ′ _F is the reduced form of the noise fraction expressed in equation (2.7.46) for the case of q = 0 (as the reference point is located on the side of the start point) and remembering that d_λ shall be calculated using d_S (and not d_p ):