Aircraft Noise Pollution
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noise pollution Noise pollution, also known as environmental noise or sound pollution, is the propagation of noise with ranging impacts on the activity of human or animal life, most of them are harmful to a degree. The source of outdoor noise worldwide is main ...
refers to noise produced by aircraft in flight that has been associated with several negative stress-mediated health effects, from sleep disorders to cardiovascular ones. Governments have enacted extensive controls that apply to aircraft designers, manufacturers, and operators, resulting in improved procedures and cuts in pollution. Sound production is divided into three categories: * Mechanical noise—rotation of the engine parts, most noticeable when fan blades reach supersonic speeds. * Aerodynamic noise—from the airflow around the surfaces of the aircraft, especially when flying low at high speeds. * Noise from aircraft systems—cockpit and cabin pressurization and conditioning systems, and Auxiliary Power units.


Mechanisms of sound production

Aircraft noise is
noise pollution Noise pollution, also known as environmental noise or sound pollution, is the propagation of noise with ranging impacts on the activity of human or animal life, most of them are harmful to a degree. The source of outdoor noise worldwide is main ...
produced by an aircraft or its components, whether on the ground while parked such as auxiliary power units, while taxiing, on run-up from propeller and jet exhaust, during takeoff, underneath and lateral to departure and arrival paths, over-flying while en route, or during landing. A moving aircraft including the
jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
or
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
causes compression and rarefaction of the air, producing motion of air molecules. This movement propagates through the air as pressure waves. If these pressure waves are strong enough and within the audible
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
spectrum, a sensation of hearing is produced. Different aircraft types have different noise levels and frequencies. The noise originates from three main sources: * Engine and other mechanical noise * Aerodynamic noise * Noise from aircraft systems


Engine and other mechanical noise

Much of the noise in propeller aircraft comes equally from the propellers and aerodynamics. Helicopter noise is aerodynamically induced noise from the main and tail 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. In
computer model Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be deter ...
ling terms noise from a moving aircraft can be treated as a
line source A line source, as opposed to a point source, area source, or volume source, is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear (one-dimensional) geometry. The most prominent linear sources a ...
. Aircraft gas turbine engines (
jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s) are responsible for much of the aircraft noise during takeoff and climb, such as the ''buzzsaw 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. The majority of engine noise is due to jet noise—although high bypass-ratio
turbofan The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...
s 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. Engines are the main source of aircraft noise. The geared
Pratt & Whitney PW1000G The Pratt & Whitney PW1000G, also called the Geared Turbofan (GTF), is a high-bypass geared turbofan engine family produced by Pratt & Whitney. After many demonstrators, the program was launched with the Mitsubishi MRJ's PW1200G in March 2008, a ...
helped reduce the noise levels of the
Bombardier CSeries The Airbus A220 is a family of five-abreast narrow-body airliners by Airbus Canada Limited Partnership. It was originally designed by Bombardier and had two years in service as the Bombardier CSeries. The program was launched on 13 July 2 ...
,
Mitsubishi MRJ The Mitsubishi SpaceJet (, originally named ''Mitsubishi Regional Jet'') is a regional jet developed by Japanese company Mitsubishi Aircraft Corporation (MAC), a Mitsubishi Heavy Industries (MHI) subsidiary. The airframe is made mainly in alumi ...
and
Embraer E-Jet E2 The Embraer E-Jet E2 family are medium-range jet airliners developed by Embraer, succeeding the original E-Jet. The program was launched at the Paris Air Show in 2013. The first variant, the E190-E2, took its first flight on 23 May 2016 and wa ...
crossover
narrowbody aircraft A narrow-body aircraft or single-aisle aircraft is an airliner arranged along a single aisle, permitting up to 6-abreast seating in a cabin less than in width. In contrast, a wide-body aircraft is a larger airliner usually configured with mu ...
: 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. The
PowerJet SaM146 The PowerJet SaM146 is a turbofan engine produced by the PowerJet joint venture between Snecma (Safran) of France and NPO Saturn of Russia. Developing of thrust, the SaM146 is used on the Sukhoi Superjet 100. Snecma is in charge of the core eng ...
in the
Sukhoi Superjet 100 The Sukhoi Superjet 100 () or SSJ100 is a regional jet designed by Russian aircraft company Sukhoi Civil Aircraft, a division of the United Aircraft Corporation (now: Regional Aircraft – Branch of the Irkut Corporation). With development starti ...
features 3D
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
fan blades and a
nacelle A nacelle ( ) is a "streamlined body, sized according to what it contains", such as an engine, fuel, or equipment on an aircraft. When attached by a pylon entirely outside the airframe, it is sometimes called a pod, in which case it is attached ...
with a long mixed duct flow nozzle to reduce noise.


Aerodynamic noise

Aerodynamic noise arises from the airflow around the aircraft
fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...
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 from
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
s. Low-flying, high-speed military aircraft produce especially loud aerodynamic noise. The shape of the nose, windshield or
canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...
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. The
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
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: * Bluff Body Noise – the alternating vortex shedding from either side of a
bluff body In fluid dynamics, the drag coefficient (commonly denoted as: c_\mathrm, c_x or c_) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equ ...
, creates low-pressure regions (at the core of the shed vortices) which manifest themselves as pressure waves (or sound). The separated flow around the bluff body is quite unstable, and the flow "rolls up" into ring vortices—which later break down into turbulence. * Edge Noise – when turbulent flow passes the end of an object or gaps in a structure (high lift device clearance gaps) the associated fluctuations in pressure are heard as the sound propagates from the edge of the object (radially downwards).


Noise from aircraft systems

Cockpit A cockpit or flight deck is the area, usually near the front of an aircraft or spacecraft, from which a Pilot in command, pilot controls the aircraft. The cockpit of an aircraft contains flight instruments on an instrument panel, and the ...
and cabin
pressurization {{Wiktionary Pressurization or pressurisation is the application of pressure in a given situation or environment. Industrial Industrial equipment is often maintained at pressures above or below atmospheric. Atmospheric This is the process by ...
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 the
Auxiliary Power Unit An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115&n ...
(APU), an on‑board
generator Generator may refer to: * Signal generator, electronic devices that generate repeating or non-repeating electronic signals * Electric generator, a device that converts mechanical energy to electrical energy. * Generator (circuit theory), an eleme ...
used in aircraft to start the main engines, usually with
compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
, 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.


Health effects

Aircraft engines are the major source of
noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...
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. There are
health Health, according to the World Health Organization, is "a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity".World Health Organization. (2006)''Constitution of the World Health Organiza ...
consequences of elevated sound levels. Elevated workplace or other
noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...
can cause
hearing impairment Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken l ...
,
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
,
ischemic heart disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pla ...
,
annoyance Annoyance is an unpleasant mental state that is characterized by irritation and distraction from one's conscious thinking. It can lead to emotions such as frustration and anger. The property of being easily annoyed is called irritability. Ps ...
,
sleep disturbance A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are test ...
, and decreased school performance. Although some hearing loss occurs naturally with age, in many developed nations the impact of noise is sufficient to impair hearing over the course of a lifetime. Elevated noise levels can create stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors. Airport noise has been linked to high blood pressure. Aircraft noise increases risks of
heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may tr ...
s.


German environmental study

A large-scale statistical analysis of the health effects of aircraft noise was undertaken in the late 2000s by Bernhard Greiser for the
Umweltbundesamt The Umweltbundesamt (; UBA, ) is the ''German Environment Agency''. Together with the Bundesamt für Naturschutz, the Bundesamt für kerntechnische Entsorgungssicherheit and the Bundesamt für Strahlenschutz, it operates under the jurisdiction o ...
, 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.''Tödlicher Lärm''—
Spiegel Spiegel is German, Yiddish, and Dutch for "mirror". More specifically, it may refer to: Publications * '' Der Spiegel'', a weekly German magazine * Der Spiegel (online), the online sibling of ''Der Spiegel'' Political * Spiegel scandal, a 1962 ...
'', Nr. 51, 14 Dezember 2009, Page 45
The German study concluded that aircraft noise clearly and significantly impairs health. For example, a day-time average sound pressure level of 60
decibels The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a Power, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whose ...
increasing coronary heart disease by 61% in men and 80% in women. As another indicator, a night-time average sound pressure level of 55
decibels The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a Power, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whose ...
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 40
decibels The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a Power, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whose ...
.


FAA advice

The Federal Aviation Administration (
FAA The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
) 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. Communities in affected areas may be eligible for mitigation such as soundproofing.


Cabin noise

Aircraft noise also affects people within the aircraft: crew and passengers. Cabin noise can be studied to address the occupational exposure and the health and safety of pilots and flight attendants. In 1998, 64 commercial airline pilots were surveyed regarding
hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Language ...
and
tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...
. In 1999, the
NIOSH The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
conducted several noise surveys and health hazard evaluations, and found noise levels exceeding its recommended exposure limit of 85
A-weighted A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured s ...
decibels as an 8-hr
TWA Trans World Airlines (TWA) was a major American airline which operated from 1930 until 2001. It was formed as Transcontinental & Western Air to operate a route from New York City to Los Angeles via St. Louis, Kansas City, and other stops, with ...
. 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). 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. 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).


Cognitive effects

Simulated aircraft noise at 65 dB(A) has been shown to negatively affect individuals’ memory and recall of auditory information. 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. A BAC of 0.10 is double the legal limit required to operate a motor vehicle in many developed countries such as Australia.


Mitigation programs

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-bypass
turbofan The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...
engines, for example, are quieter than the
turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...
s and low-bypass turbofans of the 1960s. First, 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. In the 1980s the
U.S. Congress The United States Congress is the legislature of the federal government of the United States. It is Bicameralism, bicameral, composed of a lower body, the United States House of Representatives, House of Representatives, and an upper body, ...
authorized the
FAA The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
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 first airports at which the technology was applied were
San Francisco International Airport San Francisco International Airport is an international airport in an unincorporated area of San Mateo County, south of Downtown San Francisco. It has flights to points throughout North America and is a major gateway to Europe, the Middle E ...
and
San Jose International Airport Norman Y. Mineta San Jose International Airport , commonly known simply as San Jose International Airport, is a city-owned public airport in San Jose, California, United States. It is named after San Jose native Norman Mineta, former United Sta ...
in California. A computer model is used which simulates the effects of aircraft noise upon building structures. Variations of aircraft type, flight patterns and local
meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...
can be studied. Then the benefits of building retrofit strategies such as roof upgrading, window glazing improvement, fireplace baffling,
caulking Caulk or, less frequently, caulking is a material used to seal joints or seams against leakage in various structures and piping. The oldest form of caulk consisted of fibrous materials driven into the wedge-shaped seams between boards on w ...
construction seams can be evaluated.Hogan, C. Michael and Jorgen Ravnkilde, ''Design of acoustical insulation for existing residences in the vicinity of San Jose Municipal Airport'', 1 January 1984, FAA grant-funded research, ISBN B0007B2OG0


Regulation

Stages are defined in the US
Code of Federal Regulations In the law of the United States, the ''Code of Federal Regulations'' (''CFR'') is the codification of the general and permanent regulations promulgated by the executive departments and agencies of the federal government of the United States. ...
(CFR) Title 14 Part 36. For civil
jet aircraft A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines. Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, je ...
, the US
FAA The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
Stage 1 is the loudest and Stage 4 is quieter. Stage 3 was required for all large jet and turboprop aircraft at US civilian airports from the year 2000, and at least Stage 2 for under
MTOW The maximum takeoff weight (MTOW) or maximum gross takeoff weight (MGTOW) or maximum takeoff mass (MTOM) of an aircraft is the maximum weight at which the pilot is allowed to attempt to take off, due to structural or other limits. The analogous ...
jets until December 31, 2015. The previous was Stage 4 for large airplanes, equivalent to the
ICAO The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international a ...
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 new
type certificate A type certificate signifies the airworthiness of a particular category of aircraft, according to its manufacturing design (''type design''). It confirms that the aircraft of a new type intended for serial production, is in compliance with applica ...
s from December 31, 2017, or December 31, 2020 depending on weight. The US allows both the louder Stage 1 and quiet Stage 2
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
s. The quietest Stage 3 helicopter noise standard became effective on May 5, 2014, and are consistent with ICAO Chapter 8 and Chapter 11.


Night flying restrictions

At
Heathrow Heathrow Airport (), called ''London Airport'' until 1966 and now known as London Heathrow , is a major international airport in London, England. It is the largest of the six international airports in the London airport system (the others bei ...
,
Gatwick Gatwick Airport (), also known as London Gatwick , is a major international airport near Crawley, West Sussex, England, south of Central London. In 2021, Gatwick was the third-busiest airport by total passenger traffic in the UK, after Hea ...
and
Stansted London Stansted Airport is a tertiary international airport serving London, England, United Kingdom. It is located near Stansted Mountfitchet, Essex, England, northeast of Central London. London Stansted serves over 160 destinations acro ...
airports in
London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
, UK and
Frankfurt Airport Frankfurt Airport (; german: link=no, Flughafen Frankfurt Main , also known as ''Rhein-Main-Flughafen'') is a major international airport located in Frankfurt, the fifth-largest city of Germany and one of the world's leading financial centres ...
in Germany,
night flying restrictions Night flying restrictions or night-time curfews, including night flight bans, are any regulations or legislation imposed by a governing body to limit the ground-perceived exposure to aircraft noise pollution during the night hours, when the majorit ...
apply to reduce noise exposure at night.


Satellite-based navigation systems

A series of trials were undertaken at London's Heathrow Airport, between December 2013 and November 2014, as part of the UK's "Future Airspace Strategy", and the Europe-wide "
Single European Sky The Single European Sky (SES) is a European Commission initiative that seeks to reform the European air traffic management system through a series of actions carried out in four different levels (institutional, operational, technological and contr ...
" modernisation project. The trials demonstrated that using satellite-based navigation systems it was possible to offer noise relief to more surrounding communities, although this led to a significant unexpected rise in noise complaints (61,650 ) due to the concentrated flight paths. The study found that steeper angles for take-off and landing led to fewer people experiencing aircraft noise and that noise relief could be shared by using more precise flight paths, allowing control of the noise footprint of departing aircraft. Noise relief could be enhanced by switching flight paths, for example by using one flight path in the morning and another in the afternoon.


Technological advances


Engine design

Modern
High bypass The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for ev ...
turbofans are not only more
fuel efficient Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
, but also much quieter than older turbojet and low-bypass turbofan engines. On newer engines noise-reducing chevrons further reduce the engine's noise, while on older engines the use of
hush kit A hush kit is an Aerodynamics, aerodynamic device used to help reduce the noise produced by antique aircraft jet engines. These devices are typically installed on older turbojet and low-bypass turbofan engines, as they are much louder than late ...
s are used to help mitigate their excessive noise.


Engine location

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 within
airport An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports usually consists of a landing area, which comprises an aerially accessible open space including at least one operationally active surface ...
boundaries requires at least a 40–50 dB reduction.
Landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...
, wing slats and
wing flap A flap is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight. Flaps are usually mounted on the wing trailing edges of a fixed-wing aircraft. Flaps are used to reduce the take-off distance and the landing ...
s also produce noise and may have to be shielded from the ground with new configurations. NASA found over-wing and mid-fuselage nacelles could reduce noise by 30–40 dB, even 40–50 dB for hybrid wing body which may be essential for open rotors. By 2020,
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
technologies now 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 expand
heliport A heliport is a small airport suitable for use by helicopters and some other vertical lift aircraft. Designated heliports typically contain one or more touchdown and liftoff areas and may also have limited facilities such as fuel or hangars. I ...
s. Package delivery UAS will need to characterize their noise, establish limits and reduce their impact.


See also

*
Aviation taxation and subsidies Aviation taxation and subsidies includes taxes and subsidies related to aviation. Taxation is one of several methods to mitigate the environmental impact of aviation. Types of taxes * Airport improvement fee, paid by passengers to the airp ...
*
Electric airplane An electric aircraft is an aircraft powered by electricity. Electric aircraft are seen as a way to reduce the environmental effects of aviation, providing zero emissions and quieter flights. Electricity may be supplied by a variety of methods, ...
*
Farley v Skinner ''Farley v Skinner'' 001UKHL 49is an English contract law case, concerning the measure and availability of damages for distress. Facts Mr Farley bought a large estate, Riverside House, in Blackboys, Sussex, not far from Gatwick Airport. It had ...
*
Hush kit A hush kit is an Aerodynamics, aerodynamic device used to help reduce the noise produced by antique aircraft jet engines. These devices are typically installed on older turbojet and low-bypass turbofan engines, as they are much louder than late ...
*
Helicopter noise reduction Helicopter noise reduction is a topic of research into designing helicopters which can be operated more quietly, reducing the public-relations problems with night-flying or expanding an airport. In addition, it is useful for military applicat ...
*
Jet noise In aeroacoustics, jet noise is the field that focuses on the noise generation caused by high-velocity jets and the turbulent eddies generated by shearing flow. Such noise is known as broadband noise and extends well beyond the range of human heari ...
*
Noise barrier A noise barrier (also called a soundwall, noise wall, sound berm, sound barrier, or acoustical barrier) is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution. Noise barriers are the most effecti ...
* Rotor-stator interaction * Silent Aircraft Initiative *
Train noise Train noise is vehicle noise created by trains. Noises may be heard inside the train and outside. Subway systems, light rail transit and freight trains can send loud train noise into neighborhoods. Organizations such as the World Health Organi ...
*
XF-84H Thunderscreech The Republic XF-84H "Thunderscreech" was an American experimental turboprop aircraft derived from the F-84F Thunderstreak. Powered by a turbine engine that was mated to a supersonic propeller, the XF-84H had the potential of setting the unoffici ...
, the loudest aircraft ever built. General: *
Health effects from noise Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Noise from traffic, in particular, is considered by the World Health Organization to be one of the worst environm ...
*
Noise pollution Noise pollution, also known as environmental noise or sound pollution, is the propagation of noise with ranging impacts on the activity of human or animal life, most of them are harmful to a degree. The source of outdoor noise worldwide is main ...
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Noise regulation Noise regulation includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government. After the watershed passage of the United States Noise Control Act of 1972,U.S. Noise ...
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Aviation and the environment Like other emissions resulting from fossil fuel combustion, aircraft engines produce gases, noise, and particulates, raising environmental concerns over their global effects and their effects on local air quality. Jet airliners contribute to ...


References

*''U.S. Noise Control Act of 1972'' United States
Code In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...
Citation: 42 U.S.C. 4901 to 4918 *S. Rosen and P. Olin, ''
Hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Language ...
and
coronary heart disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pla ...
, Archives of Otolaryngology'', 82:236 (1965)


External links

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