Road traffic noise

from Wikipedia, the free encyclopedia
Noise protection measures on roads have become an integral part of the landscape. Measures such as the bundling of road and rail routes and the erection of noise barriers significantly reduce the noise impact on the environment.
Traffic noise measurement in Dresden (1972)

With road traffic noise (also briefly street noise ), the whole of the traffic generated noise called. This includes, above all, the noises generated by cars , trucks , motorized two-wheelers and trams . Sound arises u. a. by rolling noises from tires or rail wheels, the flow around the vehicle, drives and warning devices. Construction site noise from construction site vehicles and construction machinery plays a lesser role . Road traffic noise is by far the most powerful source of noise pollution in industrialized countries.


Noise is generated either directly through air turbulence or the impact of turbulent air on surfaces ( aeroacoustics ) or indirectly through structure-borne noise in bodies that are excited by vibrations, whose surfaces radiate the sound into the environment. Pressure fluctuations in the air, which are caused by road traffic noise, for example, are perceived by the human ear. In order to be able to indicate the strength of the sound, the so-called sound pressure level is determined in the unit dB at the immission location.

However, the sound pressure level is not a measure that describes the perception of sound events. Therefore, psychoacoustic relationships must also be taken into account when assessing road traffic noise. In Germany, road traffic noise is only calculated and not measured.

Knowledge of the rules for calculating sound pressure levels is essential for understanding and assessing road traffic noise. The sound pressure level is a logarithmic quantity, so special calculation rules must be observed. The human sensory impression is roughly logarithmic to the intensity of the physical stimulus ( Weber-Fechner law ). This means that the level of the physical quantity involved corresponds linearly to human perception. Human perception also depends on the frequency (pitch of sounds). For this reason, the so-called A-weighted level is used in the German-speaking area and partly throughout Europe , which can be recognized by the notation dB (A) and which takes into account the human hearing perception to some extent, see frequency weighting . From the sound pressure levels measured with a sound level meter, a time average, an equivalent continuous sound level L Aeq, T, is calculated in many cases . Special noise properties such as impulse, tone or information content are withdrawn from the assessment. A single loud motorcycle in the quiet night can make sleepers wake up, but the averaged continuous noise level over an hour is only slightly affected, and disturbing individual sources of noise can be "played down".

The following characteristics of sound perception can be determined:

  • A doubling of the sound power (e.g. two identical, incoherently vibrating sound sources instead of one) increases the sound pressure level by 3 dB (A). That means, should the traffic volume double, this leads to a sound pressure level increase of 3 dB (A).
  • In order to produce a perceived doubling or halving of the volume, the sound pressure level must be increased or decreased by around 10 dB (A).
  • If the distance to the sound source is doubled, this results in a sound pressure level reduction of 6 dB (A) outdoors. Conversely, if the distance to the sound source is halved, an increase of 6 dB (A) can be expected. This applies to point sources such as individual vehicles. Busy roads, on the other hand, can be viewed as sources of line noise; Halving or doubling the distance results in a level difference of 3 dB (A) or −3 dB (A).
  • With increasing distances to the sound source, weather influences such as wind, humidity or temperature distribution have a major impact on the sound pressure level. This can fluctuate by up to 20 dB (A) at a distance of 200 m.
  • Pure truck traffic causes a sound pressure level increase of approx. 10 dB (A) at a maximum speed of 100 km / h compared to pure car traffic. However, this value depends on the maximum permitted speed.

Mechanisms of origin

Tire-road noise

The most important mechanism for generating noise from road traffic is tire-road noise . The roughness of the road surface and the tire profile cause the tread lugs and the carcass to vibrate and emit airborne sound. In addition, air in the tire contact is displaced in the inlet and sucked in again in the outlet. This creates aerodynamic noises (so-called air pumping ). Tire-road noises are dominant over a wide speed range (from around 30–50 km / h, depending on the gear selected). They are particularly noticeable on natural stone pavement with a rough surface and wide joints and on trucks. In passenger cars, the introduction of radial tires (steel belted tires), which are more durable and safer, but also significantly louder than bias tires, has drastically increased the noise level since the 1950s. To a lesser extent, the trend contributes to ever wider tires to increase the tire noise and increase the fine dust content of the air and micro plastic strain of the seas in (see here ).

Drive noises

Drive noises are caused by the operation of the engine, gearbox and drive train of a motor vehicle as well as their auxiliary units and attachments (for example compressed air brakes , auxiliary heaters or cooling systems ). In the internal combustion engine, noises are generated by combustion pressures, pressure fluctuations in the intake and exhaust systems and mechanical forces in the valve and crank mechanism. In the case of electric drives, they arise from electromagnetic forces, in the bearings and from switching operations.

Drive noises are transmitted as airborne and structure-borne noise into the vehicle interior and, for example, via the large body to the outside and dominate - depending on the vehicle class and drive type - at low speeds and high engine power, such as when starting off.

Aerodynamic noises

At high speeds, noise-generating air turbulences are created on the body and on attachments. They are examined in aeroacoustic wind tunnels . At motorway speeds and “quiet” tire-road combinations, the aerodynamic sound sources can clearly dominate.

Other noises

Acoustic signals such as horns, bells, sirens and the like are necessary to ensure road safety. Therefore, they cannot be completely avoided. Furthermore, noises are caused by audio playback systems, vehicle alarm systems , acoustically supported hazard warning lights or by slamming doors and bonnets or rattling or banging cargo.

Influencing factors

  • Number of vehicles ( traffic volume )
  • Type of vehicles (truck, car, quad, motorcycle)
  • Structure of the drive train (motorization with Otto, diesel or electric motor, turbocharger, special equipment)
  • Floor structure (floor vibrations, structure-borne sound transmission into the building)
  • Road surface ( cobblestones , whispered asphalt )
  • Driving speed (the sound intensity of the tire-road noise increases with the third to fourth power of the speed, that of the aerodynamic noise with approximately the sixth power).
  • Mileage and age of the vehicles (wear, corrosion)
  • Driving style
  • Body shape (aeroacoustics)
  • Wheel load
  • Tire profile, tire structure, tire pressure, tire width
  • Sound-reflecting roadside development (acoustic trough, standing waves, vegetation)

For acoustical prognoses (planning of new streets and noise protection measures), the noise emitted by a street (emission level) can be calculated on the basis of some of the parameters mentioned above (in particular traffic density, truck share, permissible maximum speed, road surface). By calculating the sound propagation , which also includes the distance between the immission location and the sound source, the immission level at the closest buildings can be determined. With the help of special computer programs, extensive noise maps can be created and the effectiveness of various noise protection variants can be checked.

Statutory Regulations

The German Traffic Noise Protection Ordinance ( 16. BImSchV ) specifies immission limit values ( IGW for short ) that must not be exceeded in order to protect the population when building new roads or making significant changes to roads. In residential areas, these are 49 dB (A) at night and 59 dB (A) during the day.

Immission limit values ​​in dB (A) for noise prevention
Type of use by day at night
Hospitals, schools, old people's homes 57 47
pure and general residential areas 59 49
Core, village and mixed areas 64 54
Commercial areas 69 59
Trigger values ​​in dB (A) for noise abatement
Type of use by day at night
Hospitals, schools, old people's homes 67 57
pure and general residential areas 67 57
Core, village and mixed areas 69 59
Commercial areas 72 62

In Germany, there are the "Guidelines for Noise Protection on Roads RLS-90" and the preliminary calculation method for environmental noise on roads .

Noise prevention

When it comes to the generation of traffic noise, three directly or indirectly involved polluter groups can be named:

  • the motor vehicle manufacturers,
  • the motor vehicle operators and
  • the traffic planner.

The legislature addresses each of these three groups in separate statutory provisions.

Rules for the traffic planner

For traffic planning, this means that, in the run-up to the preparation or expansion of roads, it is taken into account how the noise pollution will be for the residents after the construction work has been completed. If the specified immission limit values ​​are exceeded, appropriate structural noise protection measures must be taken in the planning phase.

The noise exposure at the immission location is described by the rating level . The calculation method for determining the rating level is always used when a new building or a major change in roads is planned.

First of all, averaging levels L m, T (25) (day, 6: 00-22: 00) and L m, N (25) (night, 22: 00-6: 00) are determined. The relevant hourly traffic volume M and the relevant truck share p (over 2.8 t gross vehicle weight) in percent of total traffic serve as the basis. If no suitable project-related research results are available for these variables, taking into account the traffic development in the forecast period, these are determined from the average daily traffic volume (DTV) (with the help of a diagram contained in the calculation rules). The averaging level then relates to an immission location at a height of 2.25 m and a distance of 25 m from the middle of a single-lane street. In the case of two-lane roads, a substitute sound source is assumed in the middle of the outer lanes in order to simplify the calculation process. On the basis of this average level, the assessment level for a specific immission location (a residential building near the planned street) is determined with the following correction values

  • D V Correction for a permissible maximum speed other than 100 km / h
  • D StrO correction for different road surfaces
  • D Stg Correction for inclines and declines
  • D s level change due to different vertical distances s between the lane and the relevant immission location
  • D BM Level change due to ground and meteorological attenuation
  • D B Level changes due to topographical conditions, structural measures and reflections (noise barriers and walls, shielding, etc.)
  • K Surcharge for increased interference from traffic lights controlled intersections

The calculated rating level is then compared with the valid limit value. If it exceeds this, measures must be taken to lower the assessment level.

Regulations for the vehicle operator

Nocturnal speed limit to 30 km / h for reasons of noise protection in Trier

The Road Traffic Regulations (StVO) contain regulations on the use of vehicles in road traffic . The vehicle operator, the vehicle driver, is addressed here. The StVO provides for measures for reasons of noise protection , if this is necessary to protect the population. The catalog of measures includes traffic bans and restrictions, traffic diversions and speed restrictions. Traffic bans or restrictions for certain types of traffic can be limited in terms of location and time. An example of this are night driving bans for trucks or speed restrictions during the night.

Regulations for the vehicle manufacturer

Road vehicles only receive a general operating permit (ABE) and can thus be approved for road traffic if their noise emission does not exceed certain noise limit values. Since motor vehicles do not contribute to the generation of noise in road traffic in a uniform manner, different emission limit values ​​are prescribed by law for different vehicle classes .

As early as 1937, the first regulations on the permissible noise development of motor vehicles were enacted in the Road Traffic Licensing Regulations ( StVZO ). Art. 1 of § 49 stated that "motor vehicles and their trailers ... must be designed in such a way that the noise development does not exceed the level unavoidable according to the current state of the art". Section 49 also contained the guideline for noise measurement. In the course of time, this regulation was further developed, and with the guideline of 1966, the ISO R 362 measuring method for accelerated drive-by was finally adopted.

With the contract for the establishment of the European Economic Community, the European Community can also issue regulations on the nature of motor vehicles, including the permissible noise levels, with the primary aim of harmonizing commercial law and removing trade barriers. The Council Directive of February 6, 1970 on the approximation of the legal provisions of the member states on the type approval for motor vehicles and vehicle trailers (70/156 / EEC) represents the framework directive on the basis of which technical requirements can be made for the type approval of motor vehicles. The EC directive from 1966 was adopted as EC directive 70/157 / EEC with minor deviations. After a period of optional application according to national or EC regulations, the directive was adopted into national law from May 1, 1981 for new vehicle types and from October 1, 1983 for vehicles coming on the market for the first time. According to § 49 StVZO, motor vehicles for which the regulations on the permissible noise level are specified in the EC directives 70/157 EEC, 74/151 EEC and 78/1015 EEC of the European Community must comply with these regulations. The EC directives have thus become part of the StVZO.

The guidelines mentioned have been revised several times over the course of time and the limit values ​​prescribed therein have been reduced.

In June 2001, the EU Directive 2001/43 / EC on tires for motor vehicles and motor vehicle trailers was issued. Here not only the exact description of the measurement method for the sound emission of the tires is specified, but also limit values ​​for the sound pressure level when rolling by. A precisely defined road surface is prescribed for the measurements. The tests are carried out at speeds of 80 km / h for cars and 70 km / h for trucks. Measurements show, however, that when the directive came into force, all commercially available tires met the limit values ​​or were well below them. A lowering of the limit values ​​is therefore being discussed.

Noise abatement in Europe

As a result of the European Environmental Noise Directive , the member states of the European Union were initially obliged to draw up noise maps for all main roads - that was roads with more than 6 million vehicles per year or around 16,600 vehicles daily - as well as for all cities with over 250,000 inhabitants. By July 18, 2008, measures to be published in so-called action plans should be worked out to reduce noise (e.g. noise barriers or speed limits).

With the National Traffic Noise Protection Package II, the German government announced that it would lower the trigger values ​​for noise abatement on federal highways by 3 dB. By 2009, around 862 million euros had been spent on noise abatement. The release values ​​were lowered in 2010.

On July 27, 2020, the Federal Ministry of Transport and Digital Infrastructure announced that the trigger values ​​for noise abatement on existing federal highways would be reduced by 3 dB (A). The trigger values ​​for noise remediation depend on the type of use of the area. In residential areas, instead of 57 dB (A), only 54 dB (A) will have to be exceeded at night so that noise abatement measures can be implemented. Residents of federal trunk roads can submit applications from August 1, 2020.

Noise abatement in Switzerland

Homeowners who are affected by excessive noise have been able to file claims for compensation under current law since 2015 if the values ​​of the Noise Protection Ordinance are not complied with. The federal government expects traffic noise lawsuits amounting to a maximum of CHF 14 billion. An alternative would be to revoke the right to bring an action and replace it with annually recurring compensation payments. In 2020, more than a million people in Switzerland were not protected from excessive street noise. The previous noise abatement costs per protected person averaged around 6 to 9 thousand francs. In addition, external costs arise from street noise, such as health costs and loss of value on real estate, which amounted to more than two billion francs in 2016. In order to reduce these costs, more measures must be taken at the source.

Exposure of the population to road traffic noise

For example, if one calculates the width of the corridor in which the limit values ​​of the 16th BImSchV are exceeded for a typical motorway in Germany according to the guidelines for noise protection on roads (RLS-90), the result is flat terrain for the limit value valid during the day with a street at the same level with free sound propagation at a height of 10 m, a minimum of approx. 1500 m (100,000 vehicles per day, 25 percent truck share, 130 km / h maximum speed). At night, the aisle width required to comply with the limit values ​​is even significantly greater because of the lower limit value. Even for a country road with a traffic density of 10,000 vehicles per day, the necessary aisle widths of approx. 250 m (10 percent truck share, 100 km / h maximum speed) result at night.

Even a comparison of this information with reality shows that a large proportion of the residents of trunk roads have to live with noise pollution above the legal limit values. According to the Federal Environment Agency in 1999, around 30 percent of the total population in Germany was exposed to assessment levels above the limit value according to the 16th BImSchV. Different surveys in recent years consistently showed that around two thirds of the population in Germany feel disturbed by road traffic noise. This value is far above the corresponding results for rail and air traffic.

Road traffic noise can be harmful to health. As a rule, it does not lead to permanent physical hearing damage, but averaging levels above 60 dB (A) (during the day), according to findings from the German Federal Environment Agency and the World Health Organization, lead to a noticeable level, and above 65 dB (A) to a considerable level Increase in the risk of heart attack .

The noise effects also include sociologically and economically relevant downgrading processes , especially on inner-city main roads, which are subsumed under the buzzword noise ghetto . Combating street noise is therefore also a question of social justice .

Exposure to wildlife from road traffic noise

Little research has been done to date on the extent to which road traffic noise pollutes wildlife. A study in 2016 proved that the transmission of information between different bird species was disrupted by anthropogenic noise. Tits send specific warning signals to alert about the nature of the predator threats, and vertebrates also listen to these warning signals. Cardinals reliably produced predator avoidance responses in quiet trials, but all birds in noisy areas did not respond, showing that street noise is loud enough to drown this survival-related information in the noise or to be disturbed by cognitive distraction. Even at 47 dB (A), the birds no longer showed any reaction to the warning signals. The tits' warning calls are used by many species to convey predatory risks. This could explain the decreased biodiversity near roads.

In 2019, the Max Planck Institute for Ornithology examined the effects of road traffic noise on zebra finches . a. found that the noise disrupts normal stress reactions and delays the growth of zebra finches.

Road traffic noise reduction

Noise protection scheme

Measures at the point of issue

The source of the noise pollution (so-called emission location) is the road in connection with the traffic that is handled on it. Structural measures, such as the installation of porous asphalt layers (commonly also called whispered asphalt ), are part of active noise protection. For a 560 m long section of the federal highway 17 near Augsburg, a measure of this kind reduced the arithmetical proportion of residents with an increased risk of heart attack from eleven to one percent compared to conventional asphalt concrete.

To reduce the sound pressure level, speed restrictions or driving bans can be set up for certain vehicle groups. Speed ​​limits of between 60 and 120 km / h are already in place on around 80 percent of the motorways in urban areas. Recently, an increasing number of 30 km / h zones have been set up as this is an easy-to-implement and effective method of reducing noise. At too high speeds, however, the tire / road noise predominates .

A reduction in traffic volume also reduces the level. Halving the volume of traffic leads to a reduction in the sound pressure level of 3 dB (A). Reducing the volume of traffic to a tenth leads to a decrease in the sound pressure level by 10 dB (A) and thus to a halving of the subjective volume.

Behavior-related influencing possibilities are the avoidance of high engine speeds and cavalier starts as well as excessive volume of audio playback systems. This applies in particular to otherwise relatively low-noise areas.

Other ways of reducing noise are the use of quieter drives and aeroacoustically optimized vehicles. This topic is dealt with during vehicle development as part of the vehicle acoustics department. The possibility of noise abatement consists in the construction of quieter or even emission-free vehicles . With the very quiet electric cars , however, new hazards such. B. expected for pedestrians who u. a. based on the vehicle noises.

Measures on the route of propagation

There are a number of structural options for reducing the propagation of sound, which are also included in active noise protection (not to be confused with the term "active noise control" in technical acoustics, which is usually associated with anti- noise measures).

Noise protection blocks on a motorway

One of the best-known of these measures is the erection of a noise barrier or a noise barrier. The latter requires significantly more floor space than the wall, but offers options for planting. Noise barriers work primarily by interrupting the direct sound propagation path to the receiver, whereby the shortest sound path leads over the upper edge. Increased shadow formation, as with light, can only be achieved at high frequencies ; at low frequencies the wavelengths are in the order of magnitude of the wall height, which means that diffraction effects occur. Directly behind a high noise barrier, the street noise is not only quieter, but also significantly lower-frequency. Noise barriers should therefore be made as high as possible from the acoustic point of view, but this is often rejected because of the optical effect. Further acoustic advantages are achieved by absorbing surfaces, as this also prevents sound reflection on the other side of the street.

In addition to noise barriers or noise barriers, so-called wall-wall combinations can be found in many places. From a structural point of view, lowering the roadway below the ground level (street level) is far more complex. In this case, large amounts of earth have to be moved and a higher land consumption can be expected. The most far-reaching solutions are the construction of an enclosure or a road tunnel . Such measures are very cost-intensive and also often require permanent groundwater management .

Measures at the point of immission

Measures to reduce noise at the immission location are referred to as passive noise protection. In this case, the installation of soundproof windows or additional sound insulation of building walls is carried out. However, these measures are sometimes less effective than the active noise reduction mentioned above, because, for example, soundproof windows only show their full effect when they are closed.

Flap exhaust systems

Until mid-2016, it was permissible in the European Union and Switzerland to equip vehicles ex works with devices that make it possible to comply with the maximum permissible noise emission values ​​during acceptance measurements, but at the push of a button to produce a significantly increased noise level and thus the desire of individual drivers to be loud Vehicle sound to match. Since January 2016, such manipulations are no longer permitted on new motorcycles (according to UNECE-R 41.04) and since July 2016 on new cars (according to EU regulation 540/2014). End-of-life vehicles are excluded from the regulation.



  • Stephan Marks: It's too loud! A non-fiction book about noise and silence. Fischer, 1999, ISBN 3596139937 .
  • David Schmedding: Recording and evaluation of road traffic noise on the basis of geographical information systems. Nomos, Baden-Baden 2006, ISBN 978-3-8329-1955-9
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Web links

Individual evidence

  1. Frank M. Rauch: Noise protection in the tension triangle: Affected between law and politics. In: Zeitschrift für Immissionsschutz , issue 2/2015, page 72 ff.
  2. Source of noise , Austrian Federal Environment Agency
  3. ^ Wolfgang Pietzsch: Street planning , Werner Verlag, ISBN 3-8041-2949-8 , p. 226 ff.
  4. Federal Immission Control Act (BImSchG) of March 15, 1974; in the version dated May 14, 1990 . Sixteenth ordinance for the implementation of the Federal Immission Control Act (Traffic Noise Protection Ordinance - 16. BImSchV) of June 12, 1990. Federal Law Gazette Part I, pp. 1036-1048; Deutscher Fachschriften-Verlag, Wiesbaden 1990, ISBN 3-8078-8103-4
  5. Ulf Sandberg and Jerzy A. Ejsmont: Tire / Road Noise Reference Book . Informex, Kisa (Sweden), 2002, ISBN 91-631-2610-9
  6. Heinz Steven: Potential for reducing road traffic noise . Noise Congress 2000, Mannheim, 25. – 26. September 2000, full text (PDF) ( Memento of the original from January 24, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  7. ^ Helfer, M .: Aeroacoustics . In: WH Hucho: Aerodynamics of the automobile - fluid mechanics, heat engineering, driving dynamics, comfort . Vieweg, Wiesbaden 2005, ISBN 3-528-33114-3
  8. Jump up ↑ Helfer, M .: Tire-road noise and noise around vehicles . DAGA 2007, 19. – 22. March 2007, Stuttgart. Berlin: German Society for Acoustics eV, 2007, ISBN 978-3-9808659-3-7
  9. DIN 45687: 2006-05 - Acoustics - Software products for calculating noise immissions outdoors - Quality requirements and test regulations . May 2006
  10. a b Federal Immission Control Act (BImSchG) of March 15, 1974; in the version dated May 14, 1990 . Sixteenth Ordinance for the Implementation of the Federal Immission Control Act (Traffic Noise Protection Ordinance - 16th BImSchV) of June 12, 1990. Federal Law Gazette Part I, pp. 1036-1048; Wiesbaden: Deutscher Fachschriften-Verlag, 1990, ISBN 3-8078-8103-4
  11. VBUS of May 22, 2006 on the website of the Federal Environment Agency
  12. ^ H. Steven: Type Approval Noise Limitation and Emissions in Real Traffic . UBA workshop "Further Noise Reduction Potential of Motorized Road Vehicles", Berlin, 17.-18. September 2001
  13. ↑ Council Directive 70/157 / EEC of February 6, 1970 on the approximation of the laws of the member states on the permissible noise level and exhaust system of motor vehicles of February 6, 1970 (OJ EG L 42, p. 16), last amended on 14 June 2007 (OJ EU L 155, p. 49)
  14. Directive 2002/49 / EC of the European Parliament and of the Council of June 25, 2002 on the assessment and control of environmental noise , Official Journal of the European Communities of July 18, 2002
  15. see Article 8 of the Environmental Noise Directive
  16. Answer of the Federal Government to a small question: Traffic noise protection on federal roads , March 16, 2011.
  17. Trigger values ​​for noise remediation are reduced. Press release No. 33/2020. In: Internet presence. Federal Ministry of Transport and Digital Infrastructure, July 27, 2020, accessed on July 27, 2020 .
  18. Federal Noise Protection Ordinance
  19. System change to compensate noise-plagued residents in Switzerland , Swiss television
  20. Federal Department for the Environment, Transport, Energy and Communication : Road noise abatement: positive development, but still great need for action . In: , February 4, 2020, accessed on February 5, 2020.
  21. Environment NRW - data and facts . State Environment Agency North Rhine-Westphalia, Essen 2000, ISBN 3-00-006769-8
  22. Hearing damage due to noise even in children  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , ZDF from April 28, 2009@1@ 2Template: Toter Link /  
  23. Noise study by the Federal Environment Agency  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , Children's Environment Survey (KUS) 2003/06@1@ 2Template: Toter Link /  
  24. Wolfgang Babisch: The NaRoMI study - evaluation, assessment and in-depth analysis of traffic noise . In: Umweltbundesamt (Ed.): Chronic noise as a risk factor for myocardial infarction, results of the “NaRoMI” study . WaBoLu booklets 02/04, pp. I-1 - I-59, Berlin, 2004
  25. ^ Aaron M. Grade, Kathryn E. Sieving: When the birds go unheard: highway noise disrupts information transfer between bird species . In: Biology Letters . 12, No. 4, 2016, ISSN  1744-9561 . doi : 10.1098 / rsbl.2016.0113 .
  26. Traffic noise disrupts normal stress reactions and delays the growth of zebra finches. Max Planck Institute for Ornithology, October 14, 2019, accessed on November 8, 2019 .
  27. Thomas Beckenbauer: Tire-Road Noise - Reduction Potentials of the Road Surface, DAGA '03, Aachen, 18. – 20. March 2003, ISBN 3-9808659-0-8
  28. ^ Heidemarie Wende, Jens Ortscheid, Matthias Hintzsche: Noise effects of road traffic noises - effects of a low-noise road surface . Report of the Federal Environment Agency, 2004
  29. Hans Bendtsen (Ed.): Traffic management and noise reducing pavements . Danish Road Institute, Report 137, 2004
  30. Engine technology: Full droning with the flap , Die Zeit , August 15, 2013
  31. How bikers terrorize the green idyll with noise , Die Welt , October 6, 2014
  32. Flap exhaust could be banned , Focus , April 23, 2015
  33. New rules ensure less exhaust noise , Neue Zürcher Zeitung, January 6, 2016, accessed on March 10, 2016