Installed in 1996, the Airport Noise Management System (ANMS) enables the Chicago Department of Aviation (CDA) to monitor the amount of noise generated over the communities surrounding O'Hare by the aircraft operating at the Airport. The ANMS collects, analyzes and processes data from a number of sources of information including a network of 33 noise monitors around O'Hare, FAA radar data, weather data and noise complaints. For more information on the system, click here.
The CDA’s noise monitors record noise events based on threshold exceedance. Each noise event starts at the time the noise level exceeds a decibel threshold, typically slightly above the background or ambient noise level, and ends at the time the noise level returns to the threshold. For every noise event (aircraft or community) recorded by the ANMS, the CDA is reporting three noise metrics.
These three noise metrics are industry standard metrics and are calculated at the noise monitor. The metrics include the Lmax (Maximum Sound Level), the Leq (Equivalent Sound Level), and the SEL (Sound Exposure Level). The Lmax is the peak noise event in decibels, the Leq is the average sound level for the event in decibels, and the SEL is the average sound level for the event in decibels accounting for both intensity and duration. SEL takes all of the energy under the line in a sound pressure level versus time graph and compresses it to a 1 second value.
The single event noise data is uploaded to this webpage on a weekly basis as a .txt file. Each file contains: the monitor Site ID, the start date and time of the event, the date and time of the peak noise for the event, the duration in seconds of the event, and the Lmax, the Leq, and the SEL of the noise event in decibels.
The following data is preliminary data and is subject to change. Preparation of the monthly noise data includes quality assurance and quality control procedures for the data and reports. The final data will be incorporated in the monthly ANMS Reports.