Codes & Testing :: Noise Level Reduction (NLR)

Code: This standard rates a building's ability to block outdoor noise impact (typically from aircraft noise).

Enforcement: Some cities and counties

General Information: This code applies to structures in the vicinity of Air Force bases or airports (in some cities) and is designed to protect any building from excessive aircraft noise. The county or municipality in which the Air Force base or airport is located typically enforces this standard*.

When applicable, building permits will not be granted until acceptable NLR ratings are demonstrated. All Air Force bases and airports have noise contour curves, which are established by a Federal Aviation Regulation (F.A.R.) Part 150 noise study**. You must meet different NLR depending upon which noise contour curve your structure resides in. For example, a building between Ldn 65-70, must meet an NLR of 25 dB. It’s typically assumed that a standard construction will meet an NLR of 20. Within noisier areas, you must upgrade the isolation in order to comply.

The U.S. Air Force has established sound isolation standards designed to provide outdoor-to-indoor NLR of 25, 30 and 35 (found in the U.S. Air Force Recommendations for Insulation of Residential Structures Against Aircraft Noise). Although following the Air Force’s suggestions will help ensure compliance, you are still able to comply without following their step-by-step recommendations, provided a professional acoustician certifies the plans.

* Residents in some cities might qualify for state-funded aid to upgrade their homes to improve the NLR if they live within a certain distance from a public airport.
**As part of this study, the noise contour curves must be calculated and documented.

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