“[The Guideline Development Group] recommends reducing noise levels produced by wind turbines to below 45[A] dB Lden [at the most exposed façade, outdoors], as wind turbine noise above this level is associated with adverse health effects. [Lden is the average of all (12-15 hours of day, 4 hours of evening [if defined], 8-9 hours of night) levels, with evening and night levels weighted: +5 dB added to the evening levels and +10 dB to the night levels.]” —World Health Organization, Environmental Noise Guidelines for the European Region
https://www.wind-watch.org/quotes.php?t=82
