Air & Noise Compliance
Federal Community Noise Guidelines
Many federal agencies have created guidelines for use in determining noise impacts and land-use compatibility. Two commonly used guidelines are those established by the Department of Housing and Urban Development (HUD) and the Environmental Protection Agency (EPA). The criteria used by these agencies are energy-averaged one-hour and day-night average sound levels. These criteria are commonly considered the best suited for assessing various different types of communities and land uses in a broad sense; particularly for comparative purposes.
The Federal criteria used by HUD, the Department of Defense (DoD) and Department of Transportation (DOT) agencies were established for use as levels, when exceeded, should prompt federal monies to be used to help reduce the noise impacts. These levels were never established to be indicative of what is acceptable or what should be considered reasonable for people to endure. They were established for using limited funds and when these agencies must provide mitigation to affected communities. The EPA criteria were established to reflect levels that may be considered appropriate without regard to limited funds.  
HUD has established land use compatibility criteria for federally-funded housing projects to help protect public health and welfare from excessive noise. These criteria establish an Ldn range that defines normally acceptable and unacceptable land use for new construction and rehabilitation projects. The HUD Land Use Compatibility Guidelines page describes the HUD land use compatibility criteria. The HUD criteria are used to determine the land use compatibility of HUD funded residential developments and when noise abatement measures are required and can be funded through HUD.
The day‑night average sound level (Ldn) is a 24 hour, weighted average sound level that HUD, EPA, Federal Aviation Administration, Federal Transit Administration, and DoD commonly use for noise impact assessment. The Ldn is derived from hourly Leq values. Studies have shown that additional annoyance occurs during the nighttime since background sound levels are typically at their minimum and many people are noise sensitive while trying to sleep. A 10 dBA nighttime (10:00 PM to 7:00 AM) penalty is therefore added to nighttime Leq values to account for increased noise annoyance during these hours.
The EPA has published information which describes noise “cause and effect” relationships for sensitive land uses. These relationships are not standards because they do not account for the cost or feasibility of achieving these levels. These relationships are sometimes considered conservative. The EPA cause and effect relationships are presented in the EPA Community Noise Cause and Effect Relationships page.