Which organization is primarily responsible for determining the DNL contour used in property ownership considerations around airports?

• A. The Federal Aviation Administration
• B. The Environmental Protection Agency
• C. The Department of Homeland Security
• D. The National Park Service

Answer: (A)

DNL contours map how loud the area is around an airport and are used to guide property ownership and land-use decisions near airports. The organization that primarily determines these contours is the Federal Aviation Administration, which conducts noise analyses and publishes official DNL maps as part of airport master plans, environmental reviews, and noise compatibility programs. The Environmental Protection Agency may provide guidelines, but the actual contour data and policy for property considerations come from the FAA. The Department of Homeland Security and the National Park Service don’t set these contours.