Aircraft noise

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A Qantas Boeing 747-400 barely passes the houses near London Heathrow Airport .

As aircraft noise is noise that of aircraft - in particular of aircraft - is generated, respectively. Aircraft noise is now a significant environmental problem and has risen sharply since the 1970s due to the steady increase in annual aircraft movements. The problem regularly leads to disputes between airport operators and residents of the vicinity of airports (the so-called “airport neighbors”).

Aircraft noise can cause health problems for those affected, whereby the causal relationship between the exposure to aircraft noise and the medical symptoms is often difficult to determine. The most serious illnesses are cardiovascular diseases , especially high blood pressure , heart attacks and strokes . Therefore, measures are taken to avoid aircraft noise, which include both active and passive noise protection. Laws such as the German Aircraft Noise Act , ordinances and guidelines are intended to promote and enforce these measures in order to protect the population from the consequences of aircraft noise.


Noise and noise perception

Noise is basically sound that has a disruptive effect on the environment . There are various approaches to defining noise in the specialist literature. Gert Kemper and Karl-Friedrich Siebrasse draw the analogy between noise pollution and air pollution by defining noise as air pollution caused by man-made sound waves . From a scientific point of view, sound can be measured objectively through sound pressure levels ; However, this approach is widely criticized because of the lack of consideration of the subjective component in the literature. Heinz Hoffmann and Arndt von Lüpke cite as an example that a person hardly perceives the loud music of a symphony orchestra as noise, while the dripping tap in the quiet apartment - despite the undoubtedly lower sound energy of the noises - can certainly keep him from sleeping.

Overall, despite different definition approaches, the literature largely concurs that the perception of noise is not due to physical parameters alone , but that psychological aspects play a decisive role in an individual's perception of noise . The Federal Environment Agency also comes to this conclusion when it writes: "Noise is [...] not measurable with physical devices, because the individual perceptions cannot be objectified by measuring methods." Attitude of the listener to the noise source, but also to the same people under different circumstances such as time of day , mood, state of health and others trigger a completely different noise perception.

Aircraft noise is commonly referred to as any noise that is emitted by aircraft , especially aircraft .

Sound measurement

As described in the previous section, noise cannot be measured objectively, as how it is perceived depends on subjective factors. In order to approach the problem of aircraft noise scientifically and to be able to classify aircraft noise qualitatively, objective measuring methods must be used, which is why sound measurement is used.

Sound in the air is a pressure wave that transports sound energy . It has various physically measurable properties, whereby the sound pressure (symbol ) and the sound pressure level (symbol ) are important for the quantitative description of aircraft noise . Under the sound pressure are occurring in the transmission of sound pressure fluctuations in the air, in humans the eardrum into motion, making audible sound from the inner ear is perceived, understood. The sound pressure level is mathematically derived from the sound pressure; it is the logarithmic ratio between the squared rms value of the sound pressure and a reference value, which was determined with p 0 = 20 µPa . The sound pressure level is given in the unit decibel (dB).

Subjective auditory perception of humans

In order to better represent the properties of the human ear in the measurement, the weighted sound pressure level was introduced based on the sound pressure level . For this purpose, the sound pressure level is determined and then subjected to a frequency-dependent correction value with the aid of a filter (usually A filter ). In this way, levels in frequencies that are more clearly perceived by the ear should be included in the assessment: especially in low frequency ranges, the human ear can only perceive quieter sounds poorly, and below about 16 Hz not at all ( infrasound ). In the upper frequency range, sounds from 5,000 Hz become worse and from a maximum of 20,000 Hz they become inaudible; one speaks of ultrasound . The illustration on the right shows that people can hear sounds with a frequency of around 4,000 Hz best; sometimes even sound pressure levels of −10 dB are still perceived. The weighted sound pressure level with the symbol is also given in decibels; The unit symbol dB (A) (read: "Decibel A") is then used to distinguish between weighted and unweighted sound pressure levels .

Measurement regulations

In the Aviation Act (LuftVG), the operators of German airports and airfields are obliged to continuously record the noise pollution around the airports in fixed measuring stations and to report the measurement results to the licensing authority at regular intervals. The annex to Section 3 of the Law on Protection against Aircraft Noise contains a description of the measurement process. Many cities and municipalities have commissioned the German Aircraft Noise Service to carry out additional measurements.

Interpretation of the measured values

A distinction is made between two types of sound pressure measurements: emission and immission measurements . In emission measurements, the sound of a sound source is examined, which means that in addition to the value for the sound pressure level, the distance between the sound source and the measuring point is also specified (e.g. a jet aircraft has a sound pressure level of around 105 dB at a distance of 600 meters) , whereas the distance to sound sources does not play a direct role for immission measurements (in a quiet room there is a sound pressure level of around 25 dB).

In addition, when interpreting sound pressure levels, it is important to always take into account the origin of the logarithm - this leads to the fact that sound pressure level measured values ​​cannot be compared with one another like conventional measured values ​​that arise from linear measurements. The following applies to sound pressure levels: A value is doubled by adding 3 dB. This is initially unusual, for example two sound sources with a sound pressure level of 0 dB each emit a sound pressure level of 3 dB and two very loud sound sources that each exert a sound pressure level of 100 dB on a measuring device together achieve a sound pressure level of 103 dB.

The human ear does not strictly follow the decadic logarithm for the “volume impression”, but perceives a doubling of the volume when the sound pressure level rises by around 10 dB.

To assess the exposure to aircraft noise, however, it is not sufficient to use the sound pressure level alone, because the exposure must also be classified quantitatively, since the noise exposure from aircraft noise is not constant but occurs at intervals. To classify aircraft noise that takes this aspect into account, the sound energy is measured over a certain period of time. From these measured values, evaluated noise levels are formed using an integral calculation and these are then averaged over time . This value can be interpreted as an “average noise exposure over time”. Mathematically, the averaging level corresponds to the constant background noise, which is equivalent to the intermittent noise exposure. Since it is not the sound pressure level but the sound energy that is used to determine the averaging level, short loud phases have a significantly greater influence than longer quiet phases. The symbol of the average sound level is L M .

The averaging level is sometimes harshly criticized in the literature because it belittles short-term high noise immissions if they were averaged over a longer period of time. Therefore the rating level was introduced.

Development of aircraft noise

The noise generated by an aircraft is essentially due to the engines and the noise of the air flowing around the aircraft. The sources of noise on jet engines are primarily the air currents at the compressor , at the thrust nozzle and - if available - at the afterburner . The air flow outside the engines mainly generates sound on the fuselage and the wings . In aircraft that fly at supersonic speed , the sonic boom is another noise pollution.

In contrast to most aircraft, helicopters do not have jet engines, but rather have one or more helicopter engines that drive the rotor . Jet engines use the recoil drive by bringing the air to a very high speed through the thrust nozzle and ejecting it backwards, which results in corresponding noise emissions from the air flow. On the other hand, helicopters use the principle of dynamic lift due to the rotor , whereby a considerable proportion of the noise emission occurs at the rotor.

Most civil and military aircraft have jet engines, which is why the main focus of the following explanations will be placed on this type of engine. The theory of sound generation by flow fields, which is briefly explained in more detail in the following section, is of decisive nature for the noise emission from jet engines as well as from turboprops and helicopters. In principle, the generation of sound by flow fields can be described mathematically; However, this calculation is on the one hand very complex and on the other hand is only of limited importance for practice with regard to aircraft noise, which is why it is not dealt with in detail in this article.

Aircraft noise from jet engines

schematic structure of a jet engine
Functional principle of a jet engine: (1) engine nacelle, (2) fan, (3) low pressure compressor, (4) high pressure compressor, (5) combustion chamber, (6) high pressure turbine, (7) low pressure turbine, (8) core nozzle, (9) bypass nozzle

Jet engines suck in the ambient air, accelerate it and eject it backwards at a significantly higher speed. This creates a recoil that accelerates the aircraft forward. The ambient air penetrates the engine through the air inlet and is accelerated there by a fan ("blower"). Part of the air (the “bypass flow”) is then expelled again, the rest of the air enters the compressor, where the air is compressed by shaft blades . Due to the compression , it flows into the combustion chamber, where it is mixed with the fuel, which burns immediately, as a result of which the flowing air is further heated and accelerated. It enters the turbine , which consists of turbine blades and is connected to the compressor via a shaft so that it continues to be driven. Finally, the air flowing out of the turbine is fed into the thrust nozzle , which, thanks to its geometric shape, brings the air to a very high speed and expels it.

The generation of sound when a jet engine is operated is primarily due to the blades around which the air flows, the combustion in the combustion chamber and the friction of the mechanical parts; Added to this is the noise emission from the turbulent flows generated behind the engines. The fan, the compressor and the turbine are paddle wheels, with the compressor and the turbine in particular being designed mostly in multiple stages and thus having various paddle wheels. The basic theory of sound generation by flow fields was developed in 1952 by the British mathematician Michael James Lighthill by converting the Navier-Stokes equations into a wave equation . The solution to this equation, which can be written in the form of a retarded potential , describes the sound emitted by a paddle wheel in theoretical form. Aeroacoustics is concerned with the complex formation of noises through air currents in the engine .

Propeller turbines, so-called turboprops , are a special form of jet engine with a propeller in front of the air inlet, which is driven by a drive turbine. In such engines, the noise emission is mainly caused by the propeller through the eddies that arise and can also be mathematically approximated for calculation using the retarded potential according to Lighthill. Turboprops do not have a thrust nozzle, but only an exhaust nozzle, whereby the exhaust air is expelled, which is why the exhaust gas jet has a considerably lower speed compared to the thrust jet of a conventional jet engine. The noise emissions from the exhaust gas jet are therefore negligibly low.

Some aircraft also have an afterburner that is integrated into the jet engine and installed between the turbine and the thrust nozzle. This makes use of the fact that the air flow emerging from the turbine still contains a considerable amount of oxygen , which is necessary to reduce the temperatures occurring in the engine to a level that is tolerable for the materials . The afterburner, which is only switched on by the pilot when required , injects more fuel, which significantly increases the speed of the air flow and thus the thrust of the engine. The faster airflow also increases the sound-emitting effects of the engine, in particular the vortices generated behind the engine. An engine with an activated afterburner thus sometimes generates considerably higher sound pressure levels than the same engine running at full load without an activated afterburner.

Sonic boom

If an aircraft flies at supersonic speed , a shock wave is created on the fuselage and tail of the aircraft. These shock waves propagate in the form of Mach's cone and arrive shortly after an observer has flown over him. In the case of small aircraft and at higher altitudes, these shock waves are perceived by a person as a bang, in larger aircraft or at low altitudes as two immediately successive bangs. Contrary to popular belief, the sonic boom does not only occur at the moment when the sound barrier is broken, but it occurs permanently and is exposed to all locations overflown at supersonic speed . The sonic boom of a supersonic airplane at a height of one hundred meters can generate a sound pressure level of up to 130 dB (A) and is therefore about as loud as pistol shots fired from close by.

Aircraft noise from air currents outside the engines

When an aircraft takes off, the engines work under full load and emit high sound pressure levels. the sound emission of other components is marginal in relation to this. When an aircraft approaches the landing (as well as with new flight strategies also in certain phases of take-off, see below ), however, the engines are operated at partial load; here the noise emission has a very high proportion of the total emissions due to other factors. Main factors are the Umströmungsgeräusche of high lift devices (especially slats and flaps ) and chassis .

Frequency analysis of landing noise of an A320

Research by the German Aerospace Center (DLR) and RWTH Aachen University has shown that the noise generated on the side edges of the landing flaps during the approach is roughly the same as that of the engines. At these edges tip vortices arise; Details are still unknown to this day (2013), as the flow conditions in complex three-dimensional geometries cannot yet be described analytically. The DLR is therefore currently researching noise reduction concepts through experimental tests in the wind tunnel . Interactions must also be taken into account here - for example, the eddies caused by the landing gear hit the landing flaps, where they again emit sound.

At an opening below the wing, the tank pressure equalization opening of the Airbus A320 family , a high pitched sound is produced when air flows over it (similar to blowing through a glass bottle). A metal plate can divert the air and attenuate the phenomenon by 4 dB.

Noise emissions from engine noise

Smaller-dimensioned aircraft, for example light aircraft , do not have engines, but mostly drive their propellers with a piston engine . Due to the significantly lower maximum speeds and geometric dimensions that such aircraft have, the noise emissions from air currents are usually negligible. When the engine is switched off and the engine is sailing in the air (as is the case with gliders ), these types of aircraft - unlike airliners and military aircraft, which make loud noises even with the engines theoretically switched off - produce hardly any sound on the ground. The sometimes considerable sound pressure levels generated by small aircraft are therefore exclusively due to the engine noise and the air currents caused by the propeller.

Health consequences

The health consequences caused by aircraft noise are generally difficult to identify: Only very rarely can health damage be traced back to definable events, but generally arise from long-term exposure to aircraft noise. But then it is difficult to relate the health problems of those affected specifically to aircraft noise, since the health problems caused by aircraft noise can also have other causes.

The consequences of very loud sound pressure level effects can be clearly identified, but these hardly occur in connection with aircraft noise. It is worth mentioning the high impact of a sonic boom from an aircraft flying at low altitude , these are predominantly combat aircraft . The consequences to be suffered from this can manifest themselves in pop trauma or acoustic trauma .

Unlike such sudden and one-off events, however, when identifying and assessing the medical consequences of aircraft noise, the focus is on the long-term impact of aircraft noise on people - the periods of regular or irregular exposure are usually months or many years. The causal relationship between aircraft noise and health disadvantages is difficult to establish and can therefore primarily be determined through case studies , test series and medical reports . So far, no specific sound pressure or averaging levels can be determined that are harmful or cause illness in the event of long-term exposure. The World Health Organization (WHO) warns of health impairments in the case of a nocturnal mean level with a value of at least 40 dB.

The specialist literature lists the consequences of stress as the main indirect consequences of aircraft noise . In particular, people who have a negative attitude towards aircraft noise expresses itself in the form of stress reactions . This can lead to a weakening of the immune system , cardiovascular diseases and mental illnesses, especially tinnitus , hyperacusis and phonophobia .

The following is a brief overview of the clinical pictures and the researched connections to aircraft noise.

Cardiovascular disease

Aircraft noise has an impact on the cardiovascular system and manifests itself in diseases of the system. Several case studies have shown the connection between aircraft noise and such cardiovascular diseases.

In 2010, Eberhard Greiser, former director at the Bremen Institute for Prevention Research and Social Medicine , published a study commissioned by the Federal Environment Ministry that deals with the occurrence of such clinical pictures in the vicinity of Cologne / Bonn Airport . For this purpose, the health insurance data of a million people were examined with regard to the diagnoses they were made and the drugs prescribed , and a linear relationship between cardiovascular diseases and the continuous noise level to which the examined people were exposed due to the airport was shown. With noise exposure of 60 dB (A) during the day, the risk of general cardiovascular diseases increases according to this study by 69% in men and by 93% in women; in particular, the risk of stroke increases in women by 172%. Residents of areas close to the airport, but no longer benefiting from the airport's passive noise protection measures, were most affected. A connection between aircraft noise and mental disorders was also investigated, but the study could not determine. However, it is expressly emphasized that the connection between the diseases and other risk factors such as alcohol and tobacco consumption could not be investigated.

According to a health report by the World Health Organization, 1.8% of heart attacks in Europe are caused by traffic noise of over 60 dB. The proportion of aircraft noise in this traffic noise remains open. In another study, the connection between aircraft noise and high blood pressure was examined in 2,693 test subjects in the greater Stockholm area and came to the conclusion that there is a significantly higher risk of the disease from a continuous noise level of 55 dB (A) and a maximum level of 72 dB (A) . In connection with this study, the authors were also able to demonstrate that even during sleep with increased noise exposure, blood pressure rises without the people who are used to the aircraft noise waking up.

Mental disorders

Occurring mental disorders can have various causes, some of which have not been further researched. Stress reactions are a major contributor to the occurrence of such illnesses, which manifest themselves through subjective tinnitus (a permanent noise in the ear), hyperacusis (a pathological oversensitivity to sound) and, less often, through phonophobia (a phobic disorder in connection with sound or special noises). This stress can be triggered by prolonged aircraft noise. In Germany alone, around every tenth person reports symptoms of tinnitus and 500,000 people suffer from hyperacusis.

Measures to reduce aircraft noise

Various measures have now been taken to reduce aircraft noise. The processes are basically divided into emission-reducing and immission-reducing measures (often also into active and passive noise protection). While emission-reducing measures aim to reduce the noise development directly at the source, i.e. on the airplane or helicopter, the aim of the emission-reducing methods is to minimize the noise affecting the population, animals or the environment. The latter can be achieved through various measures such as soundproofing or increasing the distance to aircraft.

Measures to reduce emissions

Through various design measures, the noise emissions from engines, propellers and rotors have been reduced significantly over the past decades. In the case of jet engines, this is mainly due to the abandonment of single- flow engines and the associated increased use of turbofan engines, along with other changes ; In propeller planes and helicopters, lower sound pressure levels can be achieved by changing the blade geometry, which enables the rotors to run at low speeds. By levying fees and take-off bans for particularly loud aircraft, as implemented in the USA and the European Union, airlines and thus indirectly aircraft and turbine manufacturers are to be urged to develop and use quieter aircraft models.

Development progress in jet engines

Advances in the development of jet engines have made it possible, in particular, to reduce the noise emitted by engines used for civil aviation to a considerable extent in comparison with engines used from the 1950s onwards .

Chevron Nozzles on the engine of a Boeing 787

The implementation of the bypass flow in jet engines, i.e. the development of jet engines from single- flow engines to turbofan engines, has a significant share in the lower noise emission . While no or only a very small bypass flow was used in the first generations of engines, modern engines generate a large part of up to 80% of the total thrust through the bypass flow, whereby the mass distribution of air in the bypass flow to that in the main flow ("bypass flow ratio") partially in a ratio of 12: 1. According to the manufacturer , the PW1124G engine , which will be installed in the Airbus 320neo among other things , reduces the sound pressure level by 15 dB (A) through the bypass flow alone, and the PW1521G engine developed for Bombardier by 20 dB (A).

With some engines it is possible to install silencers . In older aircraft with a lower bypass flow ratio , hush kits (silencer kits ) can be installed - often afterwards - , which among other things reduces the speed differences between the fast main flow and the ambient air. The disadvantage of the Hush Kits is the loss of engine performance. The “chevron nozzles” installed in the Boeing 787's engines follow a similar principle : a zigzag-shaped rear edge of the engine is intended to mix the bypass flow better with the ambient air, thereby reducing noise emissions.

Another design measure is the use of new thrust nozzles that mix the exhaust gas jet with the ambient air in a certain way, so that noise emissions are reduced. The increased distance between the stator and impeller of the compressor in modern engines also leads to a reduction in noise. Other options for reducing noise emissions include changing the geometry of the fan blades in the engine or the use of noise-absorbing material at the engine's air inlets.

Another possibility to reduce the noise emissions of the engines is to dispense with the use of the thrust reverser with more than idle power. The thrust reverser can be switched on when landing immediately after the aircraft touches down. By deflecting the jet of the engine, the thrust of the engines takes place forward, so the aircraft is braked. In civil aviation, however, aircraft are generally only allowed to fly to runways at airports on which a safe landing can be guaranteed even without the use of thrust reversers. This means that full thrust reversal is increasingly being dispensed with, since it is associated with considerable noise emissions due to the brief start-up of the turbines to high output.

Turboprops and helicopters

With turboprops , most of the sound emitted is caused by the propellers on the engines. By changing the blade geometry , propellers could be designed more effectively, which is why the speeds at which the propellers are operated can be reduced. The reduction in speed causes a reduction in aircraft noise and makes it possible to operate the engines with lower power, which leads to a further reduction in noise. A similar effect also applies to helicopters: by changing the blade geometry of the rotor, the helicopter can be operated at a lower speed in the blade tips, which has made it possible to reduce emissions.

Introduction of noise classes and charging of noise charges

The International Civil Aviation Organization (ICAO) and the airport operator are trying to persuade the airlines to use aircraft with as little noise as possible. For this purpose, the ICAO has determined the sound pressure level of all common aircraft models and made them available in a database . A total of three values ​​are determined: A measurement takes place in the middle of the runway , but 450 meters to the side of the aircraft, while the aircraft's engines are operated at full load to take off. Another measurement takes place 6,500 meters behind the runway during the take-off phase of the aircraft. The measured value is determined when the aircraft passes this point. The flight altitude of the aircraft depends on the departure procedure and internal company regulations of the airline. The third measurement takes place during the approach 2,000 meters from the runway ; the planes are then usually about 120 meters high.

The Boeing 727 falls into the second chapter of the ICAO definition and has not been allowed to take off and land in the USA since 1999 and in Europe since 2002 without subsequent measures to reduce noise.

Many large airports have introduced "noise classes" into which the aircraft models are sorted depending on the measured values ​​determined by the ICAO. A noise fee is charged for take-offs and landings of every aircraft, depending on the relevant noise class and the time of take-off or landing. The aim of this noise charge is to make particularly loud aircraft unprofitable and to make it worthwhile to invest in new aircraft and engine models that emit less noise. This division into noise classes and the determination of the noise charges is very inconsistent and depends on the airport operator. At Zurich Airport , for example, five noise classes have been introduced, while quieter aircraft are classified in higher noise classes.

The ICAO itself also issues guidelines to minimize noise pollution with technical advances and to promote the use of quieter aircraft models. For this, the ICAO for aircraft with a certificated takeoff weight of more than 9,000 kg four chapters (has Chapter ) introduced into the aircraft models are categorized. Chapters 1 and 2 include old aircraft models with single-flow engines or turbofan engines with a low bypass ratio; In most countries, such aircraft require a permit to take off, so they are no longer used in normal flight operations. In the USA, aircraft in chapters 1 and 2 have not been allowed to take off since 1999; in the European Union the ban has been in force since July 1, 2002. Since January 2006, aircraft newly put into service must meet the requirements of the fourth chapter.

Measures to reduce emissions

The immission-reducing measures to avoid aircraft noise aim to reduce the aircraft noise that has an impact on the environment. This is achieved on the one hand by the fact that aircraft take off as quickly as possible to a higher flight altitude and on approach stay at a higher flight altitude for as long as possible in order to burden a smaller area with low-flying aircraft. In the area of ​​approach procedures in particular, various methods have been developed to improve aircraft noise pollution. But other passive measures such as the use of noise protection halls and walls at airports and the construction of noise protection windows in residential buildings as well as the establishment of noise protection zones around airports also contribute to passive noise protection. Some important such measures are presented below, although the list is not complete due to the large number of methods available.

Some immission-reducing measures are prescribed or defined in more detail by national aircraft noise laws. More information can be found in the section #Legal situation .

Approach procedure

The exposure of people living near the airport depends to a large extent on the choice of the approach procedure for the aircraft, since depending on the procedure chosen, a different number of people are exposed to different sound pressure levels. In addition to the standard method of approach ( Standard Approach ), in which the final configuration of the aircraft for landing (that is extended flaps and landing gear out) reached quite early, various other methods are now being tested and researched. In some cases, considerable relief can be observed for those living near the airport.

A schematic comparison of the Continuous Descent Approach and the standard
approach procedure: The CDA flies over some areas at higher altitudes and dispenses with horizontal flight phases.

An important alternative approach procedure is the Low Power / Low Drag Approach (LP / LD), which is being developed at Frankfurt Airport , whereby the landing flaps and especially the landing gear are only extended much later - with the LP / LD the landing gear is only extended five nautical miles ( NM) extended before reaching the runway, with the standard approach procedure, however, twelve NM beforehand.

Another method is the continuous descent approach , whereby horizontal flight phases should be largely avoided during the descent . This enables the engines to be shut down to idle , while the standard approach procedure requires higher engine power due to intermediate horizontal phases. The Continuous Descent Approach can therefore lead to noise reductions, particularly in the area 55 to 18 km in front of the runway. The disadvantage of the gliding approach procedure is that it becomes more difficult to implement as the volume of traffic increases, because a horizontal flight is unavoidable when aircraft are crossing each other, and can therefore not be used or only to a limited extent at busy times at many airports - for example at night or at times of low traffic . The largest airports that use the procedure are Frankfurt and Cologne / Bonn airports ; the process is also being tested at other airports. In the final phase of the landing approach, the aircraft must be placed in the guide beam of the instrument landing system and thus maintain a fixed rate of descent, which is why there, from around 18 km in front of the runway, noise can no longer be reduced by the glide approach procedure.

An older method, which follows a principle similar to the Continuous Descent Approach, is the approach in two segments ( Two Segment Approach ), whereby in the first segment a steeper approach angle is selected and this is then reduced to the specified value in the guide beam. Aircraft noise pollution is reduced in particular by areas overflown at a greater altitude; Disadvantages are, due to the higher rate of descent, safety concerns and less comfort for the passengers.

Approach glide angle

By default, aircraft descend at an approach glide angle of 3 °, which results from the ICAO standard. If this angle is increased, the aircraft will sink at a higher rate of descent on the final approach, and the location at which the final approach is initiated will be moved closer to the runway. This leads to the fact that a certain area around the runway is flown over by the aircraft at a higher altitude and thus the noise pollution is reduced. Approach angles other than 3 degrees are only possible for all-weather flight operations level CAT I. According to ICAO PANS-OPS (Doc 8168), an approach angle of 3 degrees must be observed for all-weather flight operations levels CAT II and III.

At Frankfurt Airport, the approach angle for CAT I approaches was increased to 3.2 ° in December 2012, which means that the planes fly over the inhabited area in the south of Frankfurt around 50 meters higher. At other airports, the approach angles were sometimes increased significantly more; it was raised to 4 ° at Marseille airport , which results in the aircraft flying over the area at a distance of 10 NM in front of the runway in 4000 instead of 3000 feet (approx. 1300 instead of 1000 meters) and also 3 NM in front the runway are 300 meters higher than with an approach glide angle of 3 °. However, the steeper approach has some disadvantages; For example, due to the higher flight speed, the aircraft must extend their landing flaps and also the landing gear earlier, which leads to increased aerodynamic noise emissions. Also, not all aircraft can approach at such a steep angle. The effective overall noise reduction at a correspondingly high approach angle is therefore controversial.

Departure procedure

The noise emission can also be reduced during departure by choosing the departure procedure. First, the engines must run at high power to achieve sufficient speed for a safe start and at the start of stall to be avoided. However, as soon as a safe altitude and a sufficiently high flight speed for a stable flight condition is reached, the power of the engines can be reduced.

The noise abatement take-off procedure developed in the USA in 1978 provides for the take-off thrust to be reduced from 1000 feet (300 meters) above the ground and thus to continue take-off with a smaller angle of climb. When a flight speed of 250 knots (460 km / h) is reached, the rate of climb is increased again. First and foremost, this process enables high kerosene savings , but the low altitude of just 300 meters above the ground leads to continued high levels of noise pollution for the residents of the area overflown.

A departure procedure developed by the International Air Transport Association (IATA) recommends ascending to an altitude of 1500 feet (450 meters) with maximum engine power, then reducing engine power and increasing it again at 3000 feet (900 meters). This departure procedure relieves the people around the airport, but leads to increased fuel consumption. For this reason, a total of 14 different departure profiles were developed for different aircraft models, which should take into account the characteristics of the aircraft as best as possible.

Flight routes

Basically, when determining flight routes, attempts are made to avoid flying over metropolitan areas and to design the flight routes in such a way that more sparsely populated areas are preferably flown over. This raises the question of the extent to which it is justifiable to favor a larger community ( common good ) to the detriment of the residents in the sparsely populated areas. The choice of the standardized flight route as part of airspace planning, as well as short-term deviations from this flight route, which are usually determined by the air traffic controller , depend on a large number of and sometimes complex factors. Avoiding aircraft noise plays an important role here, but is fundamentally subordinate to flight safety .

Determination of noise protection areas

Noise protection areas are areas in the vicinity of airfields in which the continuous sound or nocturnal maximum level caused by aircraft noise exceeds certain decibel values ​​(dB). In order to prevent residential estates from growing closer to certain airfields, special structural usage restrictions and special structural noise protection apply in noise protection areas . In Germany, the areas are set up on the basis of § 2 and § 4 of the Law on Protection against Aircraft Noise (FluLärmG) by ordinance of the state governments. The extent of the individual noise protection zones is determined by mathematical models, taking into account the type and scope of the foreseeable flight operations ( Section 3 FluLärmG).

Structural noise protection measures

There are many ways of erecting noise protection structures and thereby protecting people living near the airport from aircraft noise. Some noise protection structures are used directly at the airport, so the necessary test runs of the engines are carried out at larger airports in noise protection halls, which significantly reduce the noise emitted into the environment through sound insulation. Also, noise barriers can stem the outgoing from the airport noise - but this is very limited for the noise of departing and landing aircraft, as these are very fast over the noise barriers and the aircraft noise so freely applied to the airport neighbors.

An important measure taken by residents near the airport is the use of sound-absorbing ventilation systems and soundproof windows , which reduce the noise entering the apartment through increased impermeability and the use of special window panes of different thicknesses . Soundproof windows are divided into six classes, the highest class being able to insulate more than 50 dB (A) sound.

Night flight ban

Another measure, which in particular serves to protect the population at night , is the enactment of night flight bans . However, as the name suggests, night flight bans do not generally prevent all night-time flights, but restrict the take-offs and landings of aircraft at the respective airport at night-time. The German FluLärmG does not provide for a night flight ban, but there are limited operating permits for take-offs and landings during the night at all German airports except Frankfurt-Hahn Airport . The period of validity of the night flight bans is regulated individually for each airport, as is the precise implementation. At most airports, for example, despite the ban on night flights, nocturnal take-offs and landings are permitted for certain purposes of flights such as mail flights or rescue flights or of aircraft models of certain noise classes.

Legal situation

In many countries, aircraft noise laws or other comparable ordinances have been passed to protect the population from aircraft noise , which prescribe maximum values ​​for sound pressure levels (often in the form of averaging or evaluation levels) or the use of noise protection measures. The legal situations in the German-speaking countries of Germany , Austria and Switzerland are explained below. In addition, the situation in the United States - the country with the most flight movements worldwide - and the regulations in other European countries are briefly discussed.


→ see also: List of major airports in Germany and environmental noise

In Germany, on April 3, 1971, the law on protection against aircraft noise , FluLärmG for short, came into force. An amendment to the law was passed on October 31, 2007 , which changed and expanded the previously applicable law in essential aspects. For example, the relevant assessment levels in Section 2 (2) FluLärmG were lowered by values ​​between 10 and 15 dB (A) and a night protection zone was set up, in which even lower maximum levels are to be used. For newly built or “significantly expanded” airports, lower limit values apply than for existing airports; For airfields used by the military, simplified regulations apply.

The purpose of the law is according to § 1 FluLärmG, "to ensure structural usage restrictions and structural noise protection in the vicinity of airfields to protect the general public and the neighborhood from dangers, significant disadvantages and considerable nuisance from aircraft noise."

For this purpose, so-called noise protection areas are established in the vicinity of airfields . No new residential buildings may be built in day protection zone 1, where the greatest noise pollution occurs. In day protection zone 2, the construction of “institutions in need of protection” such as schools and senior citizens' homes is not permitted, and residential buildings are only permitted under certain conditions. Owners of existing residential buildings can claim reimbursement of expenses for passive noise protection measures as well as compensation for the loss of value of the outdoor living area against the airport operator ( § 9 , § 12 FluLärmG).

The limit values ​​specified in the FluLärmG for the protection areas since 2007 also apply in the planning approval and approval procedures under aviation law ( Section 8 (1) sentence 3, Section 6 LuftVG , Section 13 FlugSchG). The Aviation Act (LuftVG) also stipulates in § 19a the continuous recording measurement of the noises caused by the approaching and departing aircraft. In addition, the LuftVG requires the establishment of aircraft noise commissions at airports above a certain size. Aircraft noise protection officers also participate in these aircraft noise commissions. Aircraft noise protection officers are z. B. trained by the Federal Association against Aircraft Noise .

In addition to the FluLärmG, there is also the Federal Immission Control Act (BImSchG) in Germany , which, among other things, also aims to protect against noise. Airfields are according to Section 2 (2) BImschG, however, is explicitly excluded from the scope of the law. Aircraft noise emanating from commercial airports for civil air traffic is, however, included in the noise reduction planning based on Section 47f BImSchG.


There is no law in Switzerland comparable to the German Aircraft Noise Act. The Zurich Aircraft Noise Index was drawn up by the Zurich Department of Economic Affairs to assess aircraft noise pollution at Zurich Airport , the largest airport in Switzerland . This model is intended to quantitatively record the number of people affected by aircraft noise at the airport.

On February 24, 2008, a referendum took place in Switzerland with the title “Against fighter jet noise in tourist areas” and the aim of generally prohibiting military flight exercises in “tourist areas” in peacetime. This popular initiative was rejected with 68.1% no votes.

The Swiss army has been issued with the intention to minimize the aircraft noise exposure of the population self-regulatory requirements. This includes avoiding jet flights on weekends, before 8 a.m. and during lunchtime, as well as restricting twilight and night flights to a frequency of one exercise per week. In addition, there are other measures such as the most frequent use of flight simulators instead of actual flights, the use of noise-insulated buildings for engine test runs and a few other methods.

There has been an aircraft noise dispute between Germany and Switzerland for many years . The reason for this is that the planes are flying over German territory on their approach to Zurich Airport with southern Baden , which means that the German population is exposed to considerable noise pollution. An agreement between the two states that was valid until 2001 was not extended, whereupon Germany issued a nighttime overflight ban in the area in 2001. The Swiss Confederation then filed a lawsuit with the European Court of Justice ; this was rejected in 2012. The two countries have since reached an agreement that the Swiss air navigation service provider skyguide has stopped directing traffic over German territory at certain times since January 2013; In return, Germany decided not to limit the number of flight movements over German territory.


In Austria, too, there is so far no law comparable to the German Aircraft Noise Act that regulates the exposure of the population to aircraft noise. In December 2009 the Federal Ministry for Transport, Innovation and Technology published a draft for an Air Traffic Immission Control Ordinance (LuIV), in which immission limit values ​​for airport residents are specified. On the basis of the draft regulation, objects that are exposed to high levels of aircraft noise should be subjected to noise-insulating measures such as the installation of sound insulation. The draft was criticized in particular because of the weak measures and the very high limit values ​​and has not yet been implemented.

The Federal Environmental Noise Protection Ordinance was enacted as early as 2006, which implements the requirements of the EC directive on assessing and combating environmental noise. This stipulates that noise maps must be drawn up for all geographic locations that exceed an L DEN of 60 dB or a nightly assessment level of 55 dB.

Other European countries

On July 18, 2002, the “Directive of the European Parliament and of the Council on the assessment and control of environmental noise” came into force. The aim of this guideline is to record the areas of the European Union that are particularly affected by environmental noise, to classify and reduce noise pollution in terms of quality. In a first step, all EU member states should create noise maps for these polluted areas, on the basis of which action plans should then be designed and implemented in order to implement the goal of noise reduction. A special type of assessment level, the day-evening-night level, was introduced as a comparable variable for assessing exposure (see also the section on #interpretation of the measured values ). The L DEN is determined in different ways in the individual countries .

Denmark has developed its own calculation method ( DANSIM ) for this purpose and applies to "particularly disruptive activities" such as parachute jumping or tug flights . In Belgium and Finland the measured values ​​are applied depending on the corresponding times of the day; The Integrated Noise Model (INM) from the United States is used for the calculations . Also, Greece and Spain use the INM, acted on certain types of noise but with values other than Belgium and Finland.

In France, another model, the Sophic Index , is used to model the loads. Italy uses the model of the assessment level presented at the beginning of this article and defines, on the basis of the measured values, the noise protection zones and associated requirements in Germany. Also, Norway and the United Kingdom use in the assessment level based dens process.

The Netherlands uses its own calculation method based on the A-weighted sound pressure level and deduces from the measured values ​​and other data from the aircraft the pollution within bedrooms around the airports.

United States

In the United States, aircraft noise was recognized as an environmental problem as early as the 1960s and solutions were sought. After the Noise Control Act for general noise prevention had been introduced in 1972 , the Aviation Safety and Noise Abatement Act was passed in 1979 .

At the beginning of the 1980s, the American government commissioned the Federal Aviation Administration (FAA) to develop programs to relieve the pressure on people bordering the airport. In this context, the FAA developed a computer model under the name Integrated Noise Model (INM) for evaluating the noise exposure of people bordering the airport, taking into account various parameters and a database with key figures for the individual aircraft models. In the meantime, several other countries are using the INM (see section Legal situation in other European countries ). Depending on the results of the calculations, passive noise protection measures in particular are issued.

Historical development and today's situation

Exposure to aircraft noise has occurred since the early days of powered flight. The aircraft noise exposure on the population can be derived from the number of flights, the type of aircraft used and the size of the populated region overflown at takeoff, climb and approach.

The first passenger aircraft have been in service since around 1914 . The size of the aircraft used and the number of flight movements increased rapidly, and in 1919 the first transatlantic flight took place . Great strides in the development of aircraft came in the 1920s to 1940s, particularly driven by the world wars .

Aircraft movements in Germany
year Flights
1975 744,000
1985 1,012,000
1995 2,034,000
2005 2,866,000
2011 3,060,000

The first associations of the population and the formation of initiatives against aircraft noise are documented from the 1950s; In the 1960s, aircraft noise was recognized as a serious environmental problem both in Europe and in the United States due to the continued sharp increase in the number of aircraft movements and the development of jet aircraft . In 1963, the “Action Group against Jet Jägerlärm” was founded in Wittmundhafen with reference to the Wittmundhafen air base and was thus one of the first of its kind in Germany. On April 1, 1971, the Aircraft Noise Act came into force in Germany , which regulated the exposure to aircraft noise for the first time has been.

The number of flight movements increased significantly between 1970 and today, due to various factors. Since the 1980s in particular, the importance of air traffic has increased very strongly and more than that of all other traffic areas; at many airports an annual increase in flight movements of over 10% was recorded. In Germany, the German air traffic control is responsible for the control of all flight movements; it registered 744,000 flights in 1975, compared with 3,060,000 million flights in 2011.

Today aircraft noise is perceived as the second largest noise problem in Germany after road traffic noise. 37% of the population feel annoyed by aircraft noise, 7% even suffer from it. In Germany there are around 600 interest groups and citizens' initiatives against aircraft noise. The political parties in Germany now attach great importance to protection against aircraft noise. While the coalition agreement for the 2009 Bundestag elections stated that the company wanted to achieve “internationally competitive operating times” at German airports, which should in particular limit night flight bans, in 2013 the coalition advocated that the “need for rest still had to be taken into account”. In 2013, Sören Bartol ( SPD ) recommended "increased noise protection in air traffic" and Alliance 90 / The Greens called for a "legal right to protection from traffic noise ".

An increase in flight movements in the European and US airspace, but especially in emerging countries , can also be expected in the future . As a result, the number of people affected by aircraft noise is likely to increase sharply. However, the increase in aircraft movements is countered by technical progress in engine development and fluid mechanics as well as the increased use of passive noise protection, so that a linear increase in aircraft noise pollution in developing countries as well as in Germany cannot be assumed across the board. It is questionable, however, to what extent technical developments will continue to compensate for the noise caused by the growing number of aircraft movements.


  • Andreas Fecker : Aircraft noise. Data and facts . 1st edition. Motorbuch-Verlag, Stuttgart 2012, ISBN 978-3-613-03400-6 .
  • Stephan Marks : It's too loud! A non-fiction book about noise and silence . Fischer-Taschenbuch-Verlag, Frankfurt am Main 1999, ISBN 3-596-13993-7 (with a text by Robert Gernhardt ).
  • Heinz Hoffmann, Arndt von Lüpke: 0 decibels + 0 decibels = 3 decibels. Introduction to the basic terms and the quantitative assessment of noise . 6th, revised and updated edition. Erich Schmidt Verlag, Berlin 1998, ISBN 3-503-03432-3 .
  • Holger Wöckel: Determination of flight procedures. Legal basis and legality requirements . Duncker & Humblot, Berlin 2013, ISBN 978-3-428-14113-5 .

Web links

Laws and Regulations

Individual evidence

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  1. Due to the logarithmized ratio to the specification of sound pressure levels, negative values ​​occur when the measured sound pressure is lower than the reference value p 0 = 20 µPa.
  2. In the specialist literature, the term "equivalent continuous sound level" can also be found for the averaging level; L EQ is then often used as a symbol .