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 Annual Noise Level Reports
The data presented summarizes the Day Night Average
Noise Levels (DNL). DNL is a 24-hour time-averaged sound exposure level with a 10 db nighttime (10PM to 7AM) weighting.
The data displays the measured aircraft DNL for each month, each
quarter, and the year-to-date measurement. Aircraft noise is noise
associated with known aircraft operations at O'Hare. The quarterly
noise levels for each site are displayed on the Aircraft DNL
Chart.The daily aircraft DNL noise level varies from day to day. This is primarily because different runways
are used under different wind conditions that affect where the aircraft fly. The Aircraft DNL
Chart plots the
monthly aircraft DNL measured at each site.
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