FAA’s use of the Day Night Average Sound Level metric (DNL) and the 65 decibel (dB) DNL threshold for significant noise has been a controversial issue for decades.  Partly in response to this controversy, FAA, at the direction of Congress, initiated a comprehensive study on the appropriateness of the 65 dB DNL noise significance threshold.  After years of delay, the FAA just released the results today, January 13, 2021, in a report entitled the Neighborhood Environmental Survey (the “Noise Survey”).  

The Noise Survey is based on over 10,000 survey responses, collected in 2016, from residents near 20 representative airports across the country.  The Noise Survey compares these 2016 responses to historic (1992) data regarding community annoyance from aircraft noise based on the well-known Schultz Curve, which is the scientific underpinning of the FAA’s noise standard and metric.  The Noise Survey found that:

• At noise levels of DNL 65 dB, between 60.1 percent and 70.9 percent of people were highly annoyed in 2016, compared to 12.3 percent in the 1992 study.
• At noise levels of DNL 60 dB, between 43.8 percent and 53.7 percent of people were highly annoyed in 2016, compared to the 6.5 percent in the 1992 study.
• At noise levels of DNL 55 dB, between 27.8 percent and 36.8 percent of people were highly annoyed in 2016, compared to 3.3 percent in the 1992 study.
• At noise levels of DNL 50 dB, between 15.4 percent and 23.4 percent of people were highly annoyed in 2016, compared to 1.7 percent in the 1992 study.

While these changes in community reaction are dramatic and are likely to be cited by some communities as evidence that the FAA’s noise threshold does not adequately examine noise impacts, the immediate implications of the Noise Survey are uncertain.  The FAA has clearly stated that additional research is needed to understand the reasons for those changes and has specifically clarified that–

[FAA] will not make any determinations on implications from these emerging research results for FAA noise policies until it has carefully considered public and other stakeholder input, and assesses the factors behind any increases in community impacts from aircraft noise exposure. Unless and until any changes become effective, all existing FAA regulations, orders, and policies remain in effect.

However, the Noise Survey comes at the same time that FAA is obligated to review and revise its existing orders concerning evaluation of environmental impacts, Orders 1050 and 5050 as a result of the recent revision to National Environmental Policy Act (NEPA) regulations adopted by the Council on Environmental Quality and other proposed environmental regulations under consideration by the U.S. Department of Transportation.  How or whether FAA’s revisions to its own environmental orders should also address the results of the Noise Survey is likely to be an important topic of discussion.

The Noise Survey did not examine the appropriateness of the DNL metric, a tool which has also come under criticism and was the subject of an earlier Congressionally mandated study.

A copy of the Noise Study can be found here and a copy of the Federal Register notice describing the Noise Study and other research can be found here.

The FAA is accepting comments on the Noise Study and the other research discussed in the Federal Register notice through March 15.

Airport sponsors who have questions regarding the Noise Survey should contact Katie van Heuven, Matt Adams, or Eric Pilsk.