Aircraft Noise Report
The Aircraft Noise Report summarizes noise measurements from each of the 33 noise monitors located around the Airport. The data presented summarizes the Day-Night Average Noise Levels (DNL). DNL is a 24-hour time-averaged sound exposure level
with a 10 decibel (dB) nighttime (10 p.m. to 7 a.m.) weighting to account for the lower background noise levels during the nighttime hours.
The data displays the measured aircraft DNL for each month and its comparison to the same month of the previous year, and it compares the current month to the 12-month average. The aircraft noise report identifies noise from the existing aircraft
operations at O'Hare. The modeled values for each monitor are shown for 1997, 2000 and the OMP Full Build-Out Noise Contours.
The aircraft noise levels for each monitor vary from month to month. This is primarily due to runways being utilized differently under changing wind conditions which effect where the aircraft fly.
