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Aircraftnoise pollution refers to noise produced by aircraft in flight that has been associated with several negative stress-mediated health effects, fromsleep disorders tocardiovascular disorders.[1][2][3] Governments have enacted extensive controls that apply toaircraft designers,manufacturers, and operators, resulting in improved procedures and cuts in pollution.
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Aircraft noise isnoise pollution produced by anaircraft or its components, whether on the ground while parked such asauxiliary power units, whiletaxiing, on run-up from propeller and jet exhaust, duringtakeoff, underneath and lateral to departure and arrival paths, over-flying while en route, or during landing. A moving aircraft including thejet engine orpropeller causescompression andrarefaction of the air, producing motion of air molecules. This movement propagates through the air aspressure waves. If these pressure waves are strong enough and within the audiblefrequency spectrum, a sensation of hearing is produced. Different aircraft types have different noise levels and frequencies. The noise originates from three main sources:
Much of the noise in propeller aircraft comes equally from the propellers andaerodynamics. Helicopter noise is aerodynamically induced noise from themain andtail rotors and mechanically induced noise from the main gearbox and various transmission chains. The mechanical sources produce narrow band high intensity peaks relating to the rotational speed and movement of the moving parts. Incomputer modelling terms, noise from a moving aircraft can be treated as aline source.
Aircraft gas turbine engines (jet engines) are responsible for much of the aircraft noise during takeoff and climb, such as thebuzzsaw noise generated when the tips of the fan blades reach supersonic speeds. However, with advances in noise reduction technologies—the airframe is typically more noisy during landing.[citation needed]
The majority of engine noise heard is due to jet noise—although high bypass-ratioturbofans do have considerable fan noise. The high velocity jet leaving the back of the engine has an inherent shear layer instability (if not thick enough) and rolls up into ring vortices. This later breaks down into turbulence. The SPL associated with engine noise is proportional to the jet speed (to a high power). Therefore, even modest reductions in exhaust velocity will produce a large reduction in jet noise.[citation needed]
Engines are the main source of aircraft noise.[4] The gearedPratt & Whitney PW1000G helped reduce the noise levels of theBombardier CSeries,Mitsubishi MRJ andEmbraer E-Jet E2 crossovernarrowbody aircraft: the gearbox allows the fan to spin at an optimal speed, which is one third the speed of the LP turbine, for slower fan tip speeds. It has a 75% smaller noise footprint than current equivalents.[4] ThePowerJet SaM146 in theSukhoi Superjet 100 features 3Daerodynamic fan blades and anacelle with a longmixed duct flow nozzle to reduce noise.[4]
Aerodynamic noise arises from the airflow around the aircraftfuselage and control surfaces. This type of noise increases with aircraft speed and also at low altitudes due to the density of the air. Jet-powered aircraft create intense noise fromaerodynamics. Low-flying, high-speed military aircraft produce especially loud aerodynamic noise.
The shape of the nose, windshield orcanopy of an aircraft affects the sound produced. Much of the noise of a propeller aircraft is of aerodynamic origin due to the flow of air around the blades. Thehelicopter main and tail rotors also give rise to aerodynamic noise. This type of aerodynamic noise is mostly low frequency determined by the rotor speed.
Typically noise is generated when flow passes an object on the aircraft, for example, the wings or landing gear. There are broadly two main types of airframe noise:
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Cockpit and cabinpressurization and conditioning systems are often a major contributor within cabins of both civilian and military aircraft. However, one of the most significant sources of cabin noise from commercial jet aircraft, other than the engines, is theAuxiliary Power Unit (APU), an on‑boardgenerator used in aircraft to start the main engines, usually withcompressed air, and to provide electrical power while the aircraft is on the ground. Other internal aircraft systems can also contribute, such as specialized electronic equipment in some military aircraft.
Aircraft engines are the major source ofnoise and can exceed 140 decibels (dB) during takeoff. While airborne, the main sources of noise are the engines and the high speed turbulence over the fuselage.[6]
There arehealth consequences of elevatedsound levels. Elevated workplace or othernoise can causehearing impairment,hypertension,ischemic heart disease,annoyance,sleep disturbance, and decreased school performance.[7] Although some hearing loss occurs naturally with age,[8] in many developed nations the impact of noise is sufficient to impair hearing over the course of a lifetime.[9][10] Elevated noise levels can create stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors.[11] Airport noise has been linked to high blood pressure.[12]Aircraft noise increases risks ofheart attacks.[13]
A large-scale statistical analysis of the health effects of aircraft noise was undertaken in the late 2000s by Bernhard Greiser for theUmweltbundesamt, Germany's central environmental office. The health data of over one million residents around the Cologne airport were analysed for health effects correlating with aircraft noise. The results were then corrected for other noise influences in the residential areas, and for socioeconomic factors, to reduce possible skewing of the data.[14]
The German study concluded that aircraft noise clearly and significantly impairs health.[14] For example, a day-time average sound pressure level of 60decibels increased coronary heart disease by 61% in men and 80% in women. As another indicator, a night-time average sound pressure level of 55decibels increased the risk of heart attacks by 66% in men and 139% in women. Statistically significant health effects did however start as early as from an average sound pressure level of 40decibels.[14]
The Federal Aviation Administration (FAA) regulates the maximum noise level that individual civil aircraft can emit through requiring aircraft to meet certain noise certification standards. These standards designate changes in maximum noise level requirements by "stage" designation. The U.S. noise standards are defined in the Code of Federal Regulations (CFR) Title 14 Part 36 – Noise Standards: Aircraft Type and Airworthiness Certification (14 CFR Part 36). The FAA says that a maximum day-night average sound level of 65 dB is incompatible with residential communities.[15] Communities in affected areas may be eligible for mitigation such as soundproofing.
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Aircraft noise also affects people within the aircraft: crew and passengers. Cabin noise can be studied to address theoccupational exposure and the health and safety of pilots and flight attendants. In 1998, 64 commercial airline pilots were surveyed regardinghearing loss andtinnitus.[16] In 1999, theNIOSH conducted several noise surveys and health hazard evaluations, and foundnoise levels exceeding its recommendedexposure limit of 85A-weighted decibels as an 8-hrTWA.[17] In 2006, the noise levels inside an Airbus A321 during cruise have been reported as approximately 78 dB(A) and during taxi when the aircraft engines are producing minimal thrust, noise levels in the cabin have been recorded at 65 dB(A).[18] In 2008, a study of Swedish airlines cabin crews found average sound levels between 78 and 84 dB(A) with maximum A-weighted exposure of 114 dB but found no major hearing threshold shifts.[19] In 2018, a study of sound levels measured on 200 flights representing six aircraft groups found media noise level of 83.5 db(A) with levels reaching 110 dB(A) on certain flights, but only 4.5% exceeded the NIOSH recommended 8-hr TWA of 85 dB(A).[20]
Simulated aircraft noise at 65 dB(A) has been shown to negatively affect individuals’ memory and recall of auditory information.[21] In one study comparing the effect of aircraft noise to the effect of alcohol on cognitive performance, it was found that simulated aircraft noise at 65 dB(A) had the same effect on individuals’ ability to recall auditory information as being intoxicated with a Blood Alcohol Concentration (BAC) level of at 0.10.[22] A BAC of 0.10 is double the legal limit required to operate a motor vehicle in many developed countries such as Australia.
In the United States, since aviation noise became a public issue in the late 1960s, governments have enacted legislative controls. Aircraft designers, manufacturers, and operators have developed quieter aircraft and better operating procedures. Modern high-bypassturbofan engines, for example, are notably more quiet than theturbojets and low-bypass turbofans of the 1960s. FAA Aircraft Certification achieved noise reductions classified as "Stage 3" aircraft; which has been upgraded to "Stage 4" noise certification resulting in quieter aircraft. This has resulted in lower noise exposures in spite of increased traffic growth and popularity.[23]
In the 1980s, theU.S. Congress authorized theFAA to devise programs to insulate homes near airports. While this does not address the external noise, the program has been effective for residential interiors. Some of the airports where the technology was first applied wereSan Francisco International Airport andSan Jose International Airport in California. A computer model is used which simulates the effects of aircraft noise upon building structures. Variations of aircraft type, flight patterns and localmeteorology can be studied. Then, the benefits of building retrofit strategies such as roof upgrading, windowglazing improvement, fireplace baffling,caulking construction seams can be evaluated.[24]
Noise stages are defined in the USCode of Federal Regulations (CFR) Title 14 Part 36.[25]For civilaircraft, the USFAA Stage 1 is the loudest and Stage 4 is the quietest.[26]Stage 3 was required for all large jet and turboprop aircraft at US civilian airports from the year 2000,[25]and at least Stage 2 for under 75,000 lb (34 t)MTOW jets until December 31, 2015.[26]The previous was Stage 4 for large airplanes, equivalent to theICAO Annex 16, Volume 1 Chapter 4 standards, while the more stringent Chapter 14 became effective July 14, 2014, and was adopted by the FAA as Stage 5 from January 14, 2016, effective for newtype certificates from December 31, 2017, or December 31, 2020 depending on weight.[25]
The US allows both the louder Stage 1 and quiet Stage 2helicopters.[26]The quietest Stage 3 helicopter noise standard became effective on May 5, 2014, and are consistent with ICAO Chapter 8 and Chapter 11.[25]
| Chapter | Year | Ch. 3 Margin | Types[28] |
|---|---|---|---|
| ------------- | ------------- | ------------- | Boeing 707,Douglas DC-8 |
| 2 | 1972 | ~+16 dB | Boeing 727,McDonnell Douglas DC-9 |
| 3 | 1978 | baseline | Boeing 737 Classic,MD-80 |
| 4 (stage 4) | 2006 | −10 dB | Airbus A320,Boeing 737NG,Boeing 767,Boeing 747-400 |
| 14 (stage 5) | 2017–2020 | −17 dB | Airbus A320,Airbus A320neo,Airbus A330,Airbus A350,Airbus A380,Boeing 737 MAX,Boeing 747-8,Boeing 757,Boeing 777,Boeing 777X (service entry by 2026-27),Boeing 787 |
AtHeathrow,Gatwick andStansted airports inLondon, UK andFrankfurt Airport in Germany,night flying restrictions apply to reduce noise exposure at night.[29][30]
Modernhigh bypass turbofans are not only morefuel efficient, but also much quieter than older turbojet and low-bypass turbofan engines. On newer enginesnoise-reducing chevrons further reduce the engine's noise,[31] while on older engineshush kits are used to help mitigate their excessive noise.
The ability to reduce noise may be limited if engines remain below aircraft's wings. NASA expects a cumulative 20–30 dB below Stage 4 limits by 2026–2031, but keeping aircraft noise withinairport boundaries requires at least a 40–50 dB reduction.[32]Landing gear,wing slats andwing flaps also produce noise and may have to be shielded from the ground with new configurations.[32] NASA found that over-wing and mid-fuselage nacelles could reduce noise by 30–40 dB to even 40–50 dB forhybrid wing bodies, which may be essential for open rotors.[32]
By 2020,helicopter technologies in development plus new procedures could reduce noise levels by 10 dB and noise footprints by 50%, but more advances are needed to preserve or expandheliports.[32] Package deliveryUAS will need to characterize their noise, establish limits and reduce their impact.[32]
Usage of satellite-based navigation systems can contribute to noise relief, trials in 2013–14 found, though results were not always beneficial due to concentrating flight paths. Changing flight angles and flight paths brought some changes in noise relief for some local people.[33][34][better source needed]
Airports and service providers increasingly use performance-based navigation (PBN) to design arrivals and departures that reduce community noise exposure. Examples include raising arrival altitudes and optimizing curved paths (e.g., RNP and RF-leg procedures) to avoid populated areas while maintaining safety and throughput. In 2024–2025, Naples Airport (Florida) initiated testing of satellite-based procedures aimed at reducing noise impacts and fuel burn, developed in collaboration with an air navigation service provider.[35][36]
Modern noise abatement strategies increasingly rely on performance-based navigation (PBN) to design flight paths that minimize community noise exposure. Using satellite-guided Required Navigation Performance (RNP) and radius-to-fix (RF) procedures, aircraft can follow precise curved routes that avoid populated areas while maintaining safe separation. Airports such as Naples Municipal Airport in Florida have implemented such procedures to raise arrival altitudes and reduce ground noise impact. These efforts represent a shift from airframe and engine-based solutions toward airspace and procedural noise management.[37][38]
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