TagDNL65(39)

This 2009 report from the Airport Cooperative Research Program (ACRP) examines how airports across the country manage aircraft noise in communities that fall outside the standard DNL 65 decibel threshold typically used in federal noise policy. Compiled by consultants from Harris Miller Miller & Hanson, Inc., the synthesis documents real-world airport practices for addressing noise concerns in lower-noise areas that are nonetheless affected by flight operations. The findings are intended to help airport operators, planners, and policymakers develop more responsive and comprehensive noise mitigation strategies beyond federally mandated boundaries.

Draft Working Paper One of the Seattle-Tacoma International Airport (Sea-Tac) FAR Part 150 Study, dated July 1998, prepared by Port Of Seattle. This inventory chapter updates the 1994 Part 150 program and covers airport physical facilities, air traffic operations activity, airspace/air traffic control, ANOMS radar data, current noise abatement program, noise complaint history, airport environs,

This Sea-Tac International Airport brochure, prepared by the Port of Seattle in Summer 1998, compares the noise footprints of Stage II jets, Stage III jets, and general aviation/commuter aircraft to help residents understand the noise impacts of different aircraft types. It explains that Stage III aircraft are significantly quieter than Stage II aircraft, and that replacing older Stage II planes with newer Stage III models would meaningfully reduce noise levels in surrounding communities. The document also defines key noise measurement terminology, including DNL (Day-Night Average Sound Level), and notes that nighttime flights carry a 10-decibel penalty in noise accounting.

This 1990 FAA document explains why the Day Night Average Sound Level (DNL) was chosen as the standard metric for measuring airport noise. DNL averages noise exposure over a full 24-hour period, applying a penalty for nighttime flights, and has been adopted by multiple federal agencies—including the EPA, DOT, HUD, and DOD—as the most reliable way to assess how aircraft noise affects surrounding communities. The FAA formally incorporated DNL into federal regulation through FAR Part 150, Airport Noise Compatibility Planning, in 1981.

In this January 1982 letter, Port of Seattle Planning Director Clifford C. Muller responds to community member Virginia Dana's concerns about the Sea-Tac Airport Noise Exposure Update Study. He addresses skepticism over the Ldn noise measurement system, defends the study's prediction that noise impact will decrease as airlines adopt quieter aircraft, and reassures Dana that shrinking noise contours do not eliminate eligibility for noise remedy programs. Muller acknowledges that the Technical Advisory Committee's input has been valuable and indicates that the upcoming Remedy Plan project will be the primary venue for addressing ongoing community concerns.