TagNoise(310)

This 2021 presentation by aviation consultant Jim Allerdice examines 'dispersion' — the practice of intentionally varying flight paths so that aircraft noise is spread across a wider area rather than repeatedly concentrated over the same neighborhoods. It explores the tension between the FAA's preference for Performance-Based Navigation (PBN/RNAV), which promotes precise, repeatable flight paths for safety and efficiency, and the concerns of communities living under those concentrated flight corridors. The material is relevant to ongoing debates about how airports like Sea-Tac can balance operational efficiency with equitable distribution of aircraft noise impacts.

The FAA conducted a large-scale Neighborhood Environmental Survey (NES) of 10,000 people near 20 U.S. airports to measure how aircraft noise affects community annoyance, finding that significantly more people are bothered by noise than older studies suggested — about 66% of respondents were highly annoyed at 65 decibels (DNL) and 20% at 50 decibels. The agency uses the Day-Night Average Sound Level (DNL) metric to measure noise exposure and is reviewing whether its longstanding 65 DNL threshold for 'significant' noise impact should be updated. The FAA is seeking public comment on these research findings before making any changes to official noise policy.

NLC Resolution #48 calls on Congress and the FAA to reduce the noise, health, and economic burdens placed on residential communities resulting from the FAA's NextGen air traffic control system, which has concentrated flight paths at low altitudes over neighborhoods. The resolution highlights concerns such as stress-related illness, hearing loss, reduced property values, and inadequate environmental review, and urges the FAA to adopt better noise measurement standards and consider community noise impacts in supersonic jet rulemaking. It also supports increased NASA funding for research into quieter aircraft engines and airframes.

Currently, FAA law has extremely complicated rules for establishing a noise boundary around airports. (A noise boundary is a geographic area inside which there is a certain acceptable noise level.) This is referred to as the DNL65. and it has several major flaws. The FAA Reauthorization Act Of 2018 attempted to address these flaws in several ways. This letter, from a caucus of Congressmen engaged on airport community issues complains to the Administrator that the spirit of the law is not being adhered to and demands that he make attempts to put his agency into compliance. The language is fairly technical, however there are a couple of basic points they raise: First, that the noise boundary be determined by actual noise measurements (currently the noise boundaries are 'modeled' and those calculations often do not reflect in any way the lived experience for residents.) Second, that the 'acceptable' noise level of sixty five decibels (hence DNL65) has been determined to be far too high to conform with current understandings of healthy living.

Washington State's Substitute House Bill 1847, signed into law on March 25, 2020, expands the aircraft noise abatement programs available to port districts by lowering the threshold for eligibility from airports serving more than 900 scheduled jet flights per day (previously 20). The law also enlarges the geographic 'impacted areas' around runways where noise relief programs—such as soundproofing, property acquisition, and transaction assistance—can be offered, extending coverage from six to ten miles north and up to thirteen miles south of runway ends, and from one to two miles from runway centerlines.