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Data updated October 22, 2026

Data updated October 22, 2026

Airport noise and property: DNL, noise maps and buyer rights

Updated October 22, 2026

Federal airport noise policy is built on DNL, a yearly average that weights night-time sound, with 65 dB DNL as the level above which homes are considered incompatible under FAA's Part 150 program. Once an airport files a noise exposure map, a buyer who knew or should have known of it has limited grounds to sue over that noise later.

Airport noise is measured and regulated as a long-term average, not as the loudness of a single overflight. The federal standard is the day-night average sound level (DNL), and the key threshold for homes is 65 dB DNL. Below that, FAA’s land use guidelines treat residential use as compatible; above it, they do not.

What DNL measures

14 CFR 150.7 defines DNL as the 24-hour average sound level, in decibels, from midnight to midnight, “obtained after the addition of ten decibels to sound levels” between 10 p.m. and 7 a.m. Noise exposure maps use the yearly DNL, the average across 365 days.

Two features follow from that definition:

  • Night counts more. A flight at 11 p.m. contributes as much to DNL as ten identical flights at noon.
  • Peaks are averaged in. An area with a few very loud events and long quiet periods can have the same DNL as one with steady moderate noise. Part 150’s appendix notes that its compatibility ranges reflect the responses of large groups of people and may not match an individual’s perception.

Part 150, the 65 dB threshold and noise exposure maps

Part 150 is FAA’s voluntary airport noise compatibility program. An airport operator that takes part submits a noise exposure map showing DNL contours of at least 65, 70 and 75 dB, based on forecast operations at least five years out, and identifies noncompatible land uses inside the 65 dB contour. FAA publishes a notice in the Federal Register when it finds a map in compliance. The operator may then submit a noise compatibility program, the set of measures it will use to reduce noncompatible uses, such as land acquisition, soundproofing, preferential runway use or changes to flight procedures.

Table 1 of the Part 150 appendix marks residential use as compatible below 65 dB DNL and not compatible above it. For the 65 to 75 dB range, where a community decides homes must be allowed, its notes call for construction that reduces outdoor-to-indoor noise by at least 25 to 30 dB; normal residential construction provides about 20 dB. Airports must revise a map when operations change enough to create a substantial new noncompatible use.

How a noise map limits later damage claims

49 U.S.C. 47506 applies to anyone who acquired property after February 18, 1980, near an airport whose noise exposure map has been submitted. If that buyer had actual or constructive knowledge of the map, they can recover damages for airport noise only by showing that after the purchase there was a significant change in the type or frequency of aircraft operations, the airport layout, flight patterns, or nighttime operations, and that the change caused the damages.

Constructive knowledge is imputed, at a minimum, if notice of the map was published at least three times in a newspaper of general circulation in the county before the purchase, or if the buyer received a copy of the map. In practice, a buyer near an airport with a published map should assume they took the existing noise into account.

The national transportation noise map

The Bureau of Transportation Statistics publishes a National Transportation Noise Map with modelled aviation, road and rail noise. The 2020 edition uses 2020 input data and was current as of October 2022 (BTS data description). Its metric is the 24-hour equivalent A-weighted sound level (LAeq, 24h), “the approximate average noise energy due to transportation noise sources over a 24-hour period” for an average annual day. Levels below 45 dB are not mapped.

BTS states that the data “are intended to facilitate the tracking of trends in transportation-related noise” and “should not be used to evaluate noise levels in individual locations and/or at specific times.” The map is a national model, not a measurement or an airport’s official contour.

DNL and LAeq 24h are not the same number

LAeq 24h is a plain 24-hour energy average. DNL is the same average after adding 10 dB to everything between 10 p.m. and 7 a.m. For the same sound, DNL is therefore equal to or higher than LAeq 24h, and the gap depends on how much of the noise happens at night:

  • with no night-time noise at all, the two are equal;
  • with noise that is steady around the clock, DNL is about 6.4 dB higher (the 9 night hours count ten times over);
  • with all the noise at night, DNL is 10 dB higher.

So a location modelled at 55 dB LAeq 24h could be anywhere from 55 to 65 dB DNL, depending on the airport’s night operations. The national map cannot tell you whether a property is inside a Part 150 65 dB DNL contour; only the airport’s noise exposure map can.

What FAA’s Neighborhood Environmental Survey found

FAA’s dose-response standard, the Schultz Curve, rests on survey data from the 1970s. To update it, FAA mailed a survey to 40,000 households near 20 representative airports starting in October 2015 and received 10,328 responses, with aircraft noise presented as one of 13 neighborhood concerns (FAA, Neighborhood Environmental Survey). FAA released the results in January 2021.

The new National Curve “shows a substantial increase in the percentage of people who are highly annoyed by aircraft noise over the entire range of aircraft noise levels considered, including at lower noise levels.” FAA said the results will inform future noise initiatives; the current Part 150 regulation still uses the 65 dB DNL threshold.

Disclosure rules: California versus Florida

California’s natural hazard disclosure statute, Civil Code 1103.4, includes a “Notice of Airport in Vicinity” statement for property within an airport influence area, warning that the property may be subject to noise, vibration or odors from airport operations. Florida’s statutory seller disclosure for homes, Fla. Stat. 689.302, concerns flood history and flood insurance (Florida flood disclosure law); we did not find a Florida statute that requires sellers to disclose airport noise. Buyers in Florida need to check noise exposure maps and local airport zoning themselves.

Miami-Dade figures by ZIP

For our ZIP reports we sampled the BTS 2020 aviation layer at every building in the 78 Miami-Dade ZIPs we cover. Across those ZIPs, 17,443 of about 551,550 buildings (3.2%) are modelled at 55 dB LAeq 24h or more, 3,067 at 60 dB or more and 6 at 70 dB or more. The highest shares are around Miami International Airport and Opa-locka Executive Airport.

ZIP Buildings At 55 dB or more At 60 dB or more
33122 (Miami) 407 86% 39%
33142 (Miami) 13,742 44% 13%
33125 (Miami) 8,569 38% 0.1%
33054 (Opa-locka) 8,546 28% 7%
33172 (Miami) 3,956 21% 2%
33166 (Miami) 6,671 21% 3%
33126 (Miami) 5,681 16% 2%
33014 (Hialeah) 5,221 11% 3%

Read these as screening figures. They are modelled 24-hour averages without the night penalty, sampled from the map’s classified layer at roughly 30 to 35 meter resolution, and BTS cautions against using them for single locations. A share at 55 dB LAeq 24h or more does not mean those buildings are inside a 65 dB DNL contour. For a specific address, find the airport’s current Part 150 noise exposure map, look at flight tracks, and visit at night and at peak departure times. The Miami-Dade overview links every ZIP report, and our methodology describes the sampling.

Questions

What noise level is considered incompatible with homes near an airport?

Under 14 CFR Part 150, residential use is compatible below 65 dB DNL. Airports in the program map DNL contours at 65, 70 and 75 dB and identify noncompatible land uses inside the 65 dB contour.

Can I sue an airport over noise after buying a home nearby?

Under 49 U.S.C. 47506, if a noise exposure map had been submitted and you had actual or constructive knowledge of it, you can recover noise damages only by showing a significant change after your purchase, such as more nighttime operations or new flight patterns, that caused the damages.

Is the federal transportation noise map the same as an airport's 65 DNL contour?

No. The national map uses a 24-hour average (LAeq) without the night-time penalty that DNL applies, and its publisher says it should not be used to evaluate noise levels in individual locations.

Sources

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