Airport Noise Abatement

Frequently Asked Questions About Mitigation

Was there a lawsuit against MAC?
How can I check to see if I qualify for noise mitigation?

How are qualifying households notified?

What kind of work is authorized by the mitigation program? 

What’s a noise contour?

What is DNL?

What is a noise exposure map?

What is Part 150?

What’s a noise abatement program?

Can the MAC still be sued over noise? 

Was there a lawsuit against the MAC?

Yes. The cities of Minneapolis, Richfield, Eagan and the Minneapolis Public Housing Authority brought a lawsuit in 2005 against the Metropolitan Airports Commission and reached a settlement (consent decree) in 2007. You can read the Consent Decree here. The terms of the agreement included obligations for MAC to provide mitigation to homes which were expected to experience increased exposure to airplane noise according to projections at the time. The consent decree, and the obligations it imposed, was due to expire and the parties involved entered into renewed discussions and decided to extend the agreement but under new terms. The parties entered into an Amendment to the consent decree in 2013 which ensured that MAC would have ongoing obligations to provide noise mitigation if noise increased by the requisite amount over three consecutive years. 

How can I check to see if I qualify for noise mitigation?

You can check the Metropolitan Airports Commission’s interactive map. Type in your home address, and the map will show if your block is eligible for mitigation, or could potentially be eligible in the future. The map displays blocks which are now eligible for mitigation and also shows blocks that have experienced a noise increase for one or two years but are not yet eligible for mitigation. Under the current noise mitigation program, a noise increase of a certain level must exist for three consecutive years before mitigation is provided. It's possible to appear on the map as reaching eligible status for one or two years, but then not achieve eligibility for mitigation. In that case, it should also means that your noise exposure has been reduced. You can visit MAC's Do I Qualify? page for general information about the mitigation program.  From here, you can also view a simple list of the addresses that are included in the year one or year two of eligibility or those addresses in year three, that are now eligible for mitigation.

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How are qualifying households notified that they’re eligible for noise mitigation?

The Metropolitan Airports Commission (MAC) notified qualifying households by letter in the spring and early summer of 2016. The actual mitigation will not begin until 2017.

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What kind of work is authorized under the mitigation program?

There are different noise mitigation packages depending on the home’s location and the the level of noise exposure. The package available to a property is also affected by whether or not the home has received some form of noise mitigation in the past. MAC sent letter to each qualifying household with details specific to the property around June of 2016. An orientation will be held in early 2017 to discuss options. Homeowners will have the work completed through contractors selected by MAC.

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What’s a noise contour? How are they determined?

Eligibility for mitigation is determined by producing noise contour maps annually each March. The maps show the average level of noise exposure for each area based on a modeling system called the Integrated Noise Model (INM). The model takes into consideration the number of planes, type of aircraft, time of day, flight tracks, and other data to calculate the noise exposure. Under this model, nighttime and early morning flights are treated as if they are 10 decibels louder than they actually are in recognition of the fact that those flights are particularly disruptive. While that's one positive aspect of INM modeling, the model has drawbacks. INM does a lot of averaging, and plugging in assumptions based on information from a database. INM averages the noise over the day which fails to capture impacts like the frequency of the planes. At the time of the original consent decree and the first amendment to the decree, INM modeling was the only acceptable way to measure noise for Federal Aviation Administration purposes. The Metropolitan Airports Commission was required to use INM modeling if it wanted to utilize certain federal dollars for mitigation purposes. The FAA has now adopted a new noise model but that model has most of the same problematic characteristics. The FAA Noise office is studying new ways to measure noise impacts. The Remote Monitoring Towers (RMT) which surround the airport do not play a role in developing the noise contours. The RMTs are used for other purposes and are sometimes compared to the contours to determine if the information is consistent. 

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What is DNL?

DNL, an acronym for Day/Night Noise Level, is the noise metric produced by the FAA's noise modeling system (the Integrated Noise Model). The system models aircraft noise levels over a 24 hour period to reach an average for each day. The noise model penalizes the noise level of aircraft operations that occur between 10 p.m. and 7 a.m. by adding ten decibels to account for the increased annoyance when ambient noise levels are lower and people are sleeping. 

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What is a noise exposure map?

A noise exposure map depicts the average noise levels surrounding an airport and is used to determine if homes are eligible for noise mitigation and if so, what kind of package. The maps show areas where the average noise level is 60 dB DNL noise or higher. The noise exposure maps are developed using the Federal Aviation Administration's computer model called the Integrated Noise Model.  The model creates the maps based on the actual flight paths flown and the airplane type used, however the noise attributed to each fight is based on information in a database that was collected in field tests. The Remote Monitoring Towers, which measure noise as planes fly over, are not used in the process of creating these maps.  

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What’s a noise abatement program?

A noise abatement program is an effort by an airport operator to reduce noise levels around an airport. Programs often include both operational measures and land use measures aimed at achieving greater compatibility between operation of the airport and land use in neighboring communities.

The airport operator uses a noise exposure map to identify the area of noise impacts associated with a particular scenario. The various elements of the noise compatibility program are then evaluated to determine the impacts on the noise contours with the intent of minimizing the area of noise impact.

Often, federal Airport Improvement Program funds can be used to pay for some corrective actions (e.g. acquiring homes or insulating existing homes) required for noise mitigation.

Examples of corrective actions that can reduce noise in buildings near airports include:

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Can the MAC still be sued over noise?

Cities Lawsuit

The cities involved in the settlement, including the City of Minneapolis and Minneapolis Public Housing Authority, have agreed that they will not sue the Metropolitan Airports Commission (MAC) over airport noise. There are several exceptions, however. The cities may be able to sue if the average noise (measured in DNL) goes up by two or more decibels in a year or if MAC builds a new runway or extends a runway that causes noise of 60 decibels or above in residential areas. However, being able to sue does not necessarily mean there is a good cause of action recognized by law. Homeowners who participate in the noise mitigation program established by the proposed settlement in the cities’ lawsuit will be asked to sign a release.

Separate Class Action Lawsuit

Homeowners who are members of the class and who did not opt out of that lawsuit are bound by the class action settlement which mirrors the terms of the cities settlement. For more information about the separate class action lawsuit, check the Zimmerman Reed website.

Homeowners who are not members of the plaintiffs’ class from the class action lawsuit and who have not signed releases as part of their participation in the cities settlement may sue over noise if they have a cause of action recognized by the law that they believe they can prove in court. You must consult your own attorney to determine what rights you may have in this regard.


Last updated Mar 8, 2019



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