Airport Noise Mitigation and Part 150 Studies
Scope & Methodology
This article examines the federal airport noise compatibility framework, including statutory requirements, the Part 150 study process, sound insulation program mechanics and scale, land acquisition authority, and the ANCA/Part 161 restriction review process. Sources include 49 U.S.C. §§ 47501–47534, 14 CFR Parts 150 and 161, FAA Aviation Environmental Design Tool (AEDT) documentation, and named program examples from SEA, SAN, ORD, and OAK airports through 2025.
Bottom Line Up Front
The DNL 65 dB threshold remains the federal boundary for residential land use compatibility, despite FAA data from 2021 showing annoyance levels of 60–71% at that threshold — a five- to six-fold increase from the 12.3% predicted by the Schultz Curve in 1978 (FAA NES, 2021). Airport noise mitigation is a voluntary planning program: Part 150 studies are not required, but AIP funding for noise projects is conditioned on an FAA-approved Noise Compatibility Program. Sound insulation accounts for the majority of remedial measures in reviewed FAA-approved Noise Compatibility Programs, including examples from SEA, SAN, ORD, and OAK airports through 2025.
The Federal Noise Compatibility Framework
Federal airport noise policy rests on a voluntary planning program, a mandatory noise certification standard, and a statutory restriction framework that together define how airports, airlines, and the FAA address aircraft noise exposure in communities surrounding airports. The three statutory pillars are:
- Aviation Safety and Noise Abatement Act of 1979 (ASNA) — Created the noise compatibility planning program, now codified at 49 U.S.C. §§ 47501–47510 and implemented through 14 CFR Part 150. This program establishes procedures for developing Noise Exposure Maps (NEMs) and Noise Compatibility Programs (NCPs).
- Airport Noise and Capacity Act of 1990 (ANCA) — Established the national aviation noise policy, required the phase-out of Stage 2 aircraft over 75,000 pounds by December 31, 1999, and created the process under 14 CFR Part 161 for FAA review of airport noise and access restrictions on Stage 3 aircraft.
- 14 CFR Part 36 — Prescribes noise certification standards for aircraft. The FAA Modernization and Reform Act of 2012 extended the Stage 2 prohibition to aircraft weighing 75,000 pounds or less.
The DNL 65 dB Threshold
All federal airport noise policy pivots on a single metric and threshold: the Day-Night Average Sound Level (DNL) at 65 decibels (dB). DNL is an annual average noise exposure measure that applies a 10 dB penalty to nighttime operations (10:00 PM to 7:00 AM) to reflect the greater intrusiveness of nighttime noise.
The land use compatibility table in 14 CFR Part 150, Appendix A, identifies which land uses are compatible at each noise level:
| Land Use | Below 65 DNL | 65–70 DNL | 70–75 DNL | 75–80 DNL | 80–85 DNL | Over 85 DNL |
|---|---|---|---|---|---|---|
| Residential (non-mobile home) | Compatible | Not compatible | Not compatible | Not compatible | Not compatible | Not compatible |
| Schools, hospitals, nursing homes | Compatible | NLR 25 required | NLR 30 required | Not compatible | Not compatible | Not compatible |
| Offices, business, professional | Compatible | Compatible | NLR 25 required | NLR 30 required | Not compatible | Not compatible |
| Agriculture (except livestock) | Compatible | Compatible | Compatible | Compatible | Compatible | Compatible |
NLR = Noise Level Reduction in dB. Standard residential construction provides approximately 20 dB NLR; a 25 NLR requirement means 5 dB of additional attenuation beyond standard construction.
The Annoyance Gap
The DNL 65 dB threshold was set in the early 1980s based on the Schultz Curve (1978), which predicted that 12.3% of the population would be "highly annoyed" at DNL 65 dB. The Federal Interagency Committee on Noise (FICON) revalidated the Schultz Curve in 1992.
The FAA's Neighborhood Environmental Survey (NES), released January 13, 2021, surveyed over 10,000 residents near 20 airports in 2016 and found a different relationship between noise exposure and annoyance:
| DNL Level | 1992 Schultz Curve (% highly annoyed) | 2016 NES (% highly annoyed) |
|---|---|---|
| 50 dB | 1.7% | 15.4–23.4% |
| 55 dB | 3.3% | 27.8–36.8% |
| 60 dB | 6.5% | 43.8–53.7% |
| 65 dB | 12.3% | 60.1–70.9% |
The FAA stated upon release that "additional research is needed to understand the reasons for those changes" and that it "will not make any determinations on implications" pending further review. The FAA commenced a Noise Policy Review in early 2024; the FAA Reauthorization Act of 2024 (P.L. 118-63, signed May 2024) subsequently mandated this review. As of March 2026, the DNL 65 dB threshold remains unchanged.
14 CFR Part 150: The Study Process
A Part 150 study is a voluntary program administered by the FAA that allows airport operators to assess aircraft noise exposure and develop measures to reduce and prevent incompatible land uses. Participation in Part 150 is not required, but it is a prerequisite for AIP grant funding of noise mitigation projects.