Noise Contours and the 2003 NEM

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Noise contours represent noise levels resulting from aircraft operations. The contours are developed with an FAA specified computer model called the Integrated Noise Model, or INM. The Day-Night Average Sound Level (DNL) contours represent an average day of aircraft operations at the Airport.

The INM develops the contours based on such conditions as a database of measured noise levels for individual aircraft, flight track information, aircraft fleet mix, aircraft profiles and terrain. Aircraft operations that occur between 10:00 p.m. and 7:00 a.m. are penalized with an additional 10 decibels (dB) to account for the fact that most people are sleeping at this time in a residential area. The FAA has established the DNL 65 dB contour as the minimum level for eligibility for the Residential Sound Solutions Program.

What is a Noise Exposure Map (NEM) and a DNL?

Often called "contour" maps because they define contours of noise around the Airport, these maps show where aircraft noise occurs in and around the Airport and at what sound level.

NEMs are developed using a specialized computer model developed by the FAA known as the Integrated Noise Model (INM). The FAA requires the consideration of "significant" noise levels, defined as DNL 65 dB - DNL 75 dB in residential communities surrounding the Airport.

The Day-Night Average Sound Level (DNL) is the average noise level over a 24-hour period, including an increase of 10-dB between the hours of 10 p.m. and 7 a.m. to account for the added intrusiveness of noise during these times. The 10-dB penalty means that one nighttime sound event is equivalent to 10 daytime events of the same level.