How are noise contours determined – how are they figured?
Day-Night Average Sound Level (DNL) noise contours are developed by a computerized simulation of aircraft activity at an installation and reflect site-specific operational data based on Average Annual number of 24-hour day operations. Operational data includes flight tracks, type and mix of aircraft, aircraft profiles (airspeed, altitude, and power settings), frequency and times of operation. Operations occurring between 10:00 p.m. and 7:00 a.m. incur a 10 db noise penalty as these operations occur during sleeping hours for most people. At a minimum, noise contours for DNL 60, 65, 70, 75, and 80 shall be plotted on maps for Navy and Marine Corps air installations.
