Equivalent A‐Weighted SPL Leq, Day–Night Level Ldn, and Day–Evening–Night Level Lden

In recent years some countries have continued to use NEF or NNI or similar noise measures or descriptors related to those that include a weighting based on the number of aircraft movements [29]. However, because they are much simpler to measure and seem to give adequate correlation with subjective response, there has been a move in several countries toward the use of L_eq and L_dn [29]. In the United Kingdom L_eq has been adopted with an 18‐hour period only (07:00–23:00) (because nighttime flights are normally restricted). The European Union has specified the use of L_den (DENL) to evaluate aircraft noise, which includes three periods: day, evening, and night, from which L_den is calculated. In the United States since publication of the EPA’s Levels document [31] and other similar publications, the use of CNR and NEF has been superseded by the DNL (L_dn ) for the assessment of the potential impacts of noise and for planning recommendations and land‐use management near civilian and military airports.