noise

Aircraft Noise Regulation

Aircraft noise has long been regulated through technology standards for aircraft engines.  The United States, through the Federal Aviation Administration (FAA), has worked closely with the International Civil Aviation Organization (ICAO) to develop international noise certification standards.  Initially, in 1969, the U.S. enacted aircraft noise regulations, known as Stage 2, for new large aircraft designs.  The U.S. Stage 2 regulations were similar to, but slightly different than the ICAO Chapter 2 Noise Certification Standard adopted on April 2, 1971.  In 1977, the United States enacted more stringent, Stage 3, standards.  The enactment of Stage 3 coincided with ICAO’s Chapter 3 Noise Certification Standard.  In 1999, the U.S. noise regulations were harmonized with the ICAO Annex 16 Noise Certification Standards.  In 2001, ICAO issued the Chapter 4 Noise Certification Standard to take effect on January 1, 2006 for new aircraft designs.  The FAA thereafter adopted the ICAO Chapter 4 Noise Certification Standard through agency rulemaking.

Technological Advancements

The innovative engine design on the new Boeing 787, above, significantly reduces engine noise, and includes the saw-tooth trailing edge seen clearly in the photo.

Aircraft manufacturers have conducted extensive research to further reduce noise, resulting in the technological improvements that enabled aircraft to meet Stage 4 standards. These advancements include use of noise absorbing materials in engines, advanced nacelle design, mechanical engine refinements and airframe adjustments.

Noise reduction is a major factor in current and future aircraft designs, but any modifications for noise reduction must be compatible with requirements for emissions, fuel burn, aircraft performance, cost and operating performance. Aircraft engine design must allow for the inevitable physical tradeoffs between noise and emissions reductions, limitations that have not yet been overcome by technological advances, although manufacturers and engineers work hard to find the optimal tradeoff. Noise reduction technologies (exhaust mixing; noise absorbing, insulating or shielding materials; designs with higher bypass ratio and lower fan pressure ratio) can increase CO2 and NOx emissions. At the same time, increased engine pressure and bypass ratios, which decrease fuel burn and therefore CO2, increase NOx emissions and can increase noise.

Notwithstanding the tradeoffs that exist between noise and emissions, airlines and airframe manufacturers are committed to making technological advancements to continue to reduce both noise and emissions. 

ATA airlines employ a number of operations and procedures while flying to minimize and mitigate noise. Aircraft follow noise abatement procedures in the vicinity of airports to minimize noise exposure to surrounding areas. These procedures include continuous descent approach/arrival (CDA), which limits both noise and emissions around airports. CDA has been shown to reduce peak noise levels by five or six decibels along parts of the flight path. Researchers also are exploring Quiet Climb, a thrust management option used to automate low-noise departure procedures.

The modernization of air traffic management (ATM) system will bring shorter routes, thus decreasing both delays and emissions, and allow for more precise routes to further limit noise exposure. Improved ATM also will allow more CDA procedures to occur, even during high-traffic time periods. Because of the limitations of the outdated, radar-based ATM system, CDA cannot always be employed. However, ATA airlines utilize CDA wherever possible. The modernization of the ATM system also will reduce congestion and optimize airport ground and terminal airspace operations, which will reduce both noise and emissions.

The Airport Noise and Capacity Act (ANCA), which allows for a process to monitor and minimize noise in and around airports, provides additional means for addressing aircraft noise. Enacted in 1990, ANCA ensures that, before adopting new noise restrictions, airport proprietors must obtain the FAA’s approval in order to protect the interests of airlines, airports, airport communities, the flying public and the national aviation system. This procedure can be used to address acute noise scenarios without enacting blanket restrictions on aircraft at all airports. ANCA also affords the involved parties a forum for public debate and comment and ensures a rational and legally defensible process for responsible decision making within an overarching federal framework.