# 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 2.7.24: Weighted equivalent sound levels

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

Time-weighted equivalent sound levels, which account for all significant aircraft sound energy received, shall be expressed in a generic manner by the formula
L eq,W = 10 × lg t 0 T 0 × ∑ i = 1 N g i × 10 L E,i ∕ 10 + C
(2.7.56)
The summation is performed over all N noise events during the time interval T 0 to which the noise index applies. LE,i is the single event noise exposure level of the i-th noise event. gi is a time-of-day dependent weighting factor (usually defined for day, evening and night periods). Effectively gi is a multiplier for the number of flights occurring during the specific periods. The constant C can have different meanings (normalising constant, seasonal adjustment etc.).
Using the relationship
g i = 10 Δ i ∕ 10
where Δi is the decibel weighting for the i-th period, equation (2.7.56) can be rewritten as
L eq,W = 10 × lg t 0 T 0 ∑ i = 1 N 10 L E,i + Δ i ∕ 10 + C
(2.7.57)
i.e. the time-of-day weighting is expressed by an additive level offset.

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Source: https://www.legislation.gov.uk/eudr/2015/996/annex/division/ASSESSMENT/division/2/division/2.7/division/2.7.24 (the official version)
Page: https://openlegislation.uk/eu-directive-2015-996/annex/division-ASSESSMENT/division-2/division-2.7/division-2.7.24
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.