Aircraft noise

Aircraft noise

Aircraft noise is defined as sound produced by any aircraft or its components, during various phases of a flight, on the ground while parked such as auxiliary power units, while taxiing, on run-up from propeller and jet exhaust, during take off, underneath and lateral to departure and arrival paths, over-flying while en route or during landing.Fact|date=September 2008

During take-off some aircraft may generate sound levels in excess of 100 decibels at ground level, with approach and landing creating lower levels. Since aircraft landing in inner-city airports are often lower than 60 meters (200 ft) above roof level, a sound level above 100 dBA can be realized.Fact|date=September 2008

Mechanisms of sound production

A moving aircraft including the jet engine or propeller 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 spectrum, a sensation of hearing is produced. Different aircraft types have different noise levels and frequencies. The noise originates from three main sources:

*Aerodynamic noise
*Engine and other mechanical noise
*Noise from aircraft systems

Aerodynamic noise

Aerodynamic noise arises from the airflow around the aircraft fuselage 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 aerodynamics, which is typically broadband. Low-flying, high-speed military aircraft produce especially loud aerodynamic noise.

The shape of the nose, windshield or canopy 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 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, 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. cite web
url =
title =Aircraft Airframe Noise - Research Overview
accessdate = 2008-07-13

*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).

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 modelling terms noise from a moving aircraft can be treated as a line source.

Aircraft Gas Turbine engines (Jet Engines) are responsible for much of the aircraft noise during takeoff and climb. However, with advances in noise reduction technologies - the airframe is typically more noisy during landing.Fact|date=May 2008

The majority of engine noise is due to Jet Noise - although high bypass-ratio turbofans 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 of course later breaks down into turbulence. The SPL associated with engine noise is proportional to the jet speed (to a high power) therefore, even modest reduction s in exhaust velocity will see a large reduction in Jet Noise.Fact|date=May 2008

Noise from aircraft systems

Cockpit and cabin pressurisation 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 (or APU). An Auxiliary Power Unit is an on-board generator used in aircraft to start the main engines, usually with compressed air, and to provide electrical power while the aircraft is on the ground. Other internal aircraft systems can also contribute, such as specialised electronic equipment in some military aircraft.

Annoyance effects

Lesser intensities of noise are produced for cruising velocities, mainly due to the altitudes of operation. This noise is more clearly heard in countryside settings where this noise can be intrusive even if much less in amplitude (say approximately 45 decibels). Landing aircraft descend on a three degree glide path towards an aiming point approximately 300 meters from the runway threshold. This places them at 60 meters (200 ft) above the ground at about 1200 meters (4,000 ft) from the aiming point or 900 meters (3,000 ft) from the start of the runway. This distance is usually outside the airport fence. Departing aircraft normally are over 150 meters (500 ft) above the ground before crossing the end of the runway.

Health effects of aircraft noise

The annoyance effects of aircraft noise are widely recognized; however, aircraft noise is also responsible for a significant amount of hearing loss as well as a contributor to a number of diseases. Only in the early 1970s did aircraft noise become a widespread topic of concern in the U.S. and federal regulations began to recognize the significance of abating these impacts in the vicinity of major commercial airports.High levels of aircraft noise that may exist near major commercial airports are known to increase blood pressure and contribute to hearing loss. Some research indicates that it contributes to heart diseases, immune deficiencies, neurodermatitis, asthma and other stress related diseases. Further research is being carried out to better understand these effects.

Research indicates that hearing loss is less a product of aging than a result of exposure to transportation related noise (Rosen, 1965). Any sound louder than normal conversation can damage the delicate hair cells in the cochlea, the structure in the inner ear that converts sound waves into auditory nerve signals. Initially damage to the cochlea may be temporary, but with repeated exposure, the damage becomes permanent and tinnitus may develop. More recently the Centers for Disease Control and Prevention's (CDC) National Center for Environmental Health (NCEH) conducted an analysis to determine the prevalence of hearing loss among children using data collected from 1988-1994 in the Third National Health and Nutrition Examination Survey. The analysis indicates that 14.9% of U.S. children have low or high frequency hearing loss of at least 16 dB hearing level in one or both ears.

From research of the National Institutes of Health, roughly 65 million Americans are exposed to sound levels that can interfere with their function at work or disrupt sleep, and 25 million are exposed to health risk (cardiovascular, immunological, etc.) from environmental noise.

Noise 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 engines, for example, are quieter than the turbojets 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 authorized the FAA 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 and San Jose International Airport in California. A computer model is used which simulates the effects of aircraft noise upon building structures. Variations of aircraft type, flight patterns and local meteorology can be studied. Then the benefits of building retrofit strategies such as roof upgrading, window glazing improvement, fireplace baffling, caulking construction seams can be evaluated.(Hogan, 1984).

Another idea to reduce aircraft noise on communities is floating airports which would be situated many miles out to sea. There are major drawbacks to this solution including expense, time and inconvenience to travelers in reaching such an airport. This includes the inability to integrate at-sea-airports with transport networks or proximity to business and cargo infrastructure.

Night flying restrictions

At Heathrow, Gatwick and Stansted airports in the UK, and Frankfurt Airport in Germany, night flying restrictions apply to reduce noise exposure at night. cite web|url =|title =Night flying restrictions at Heathrow, Gatwick and Stansted Airports|accessdate = 2008-07-12|last = Dept for Transport|authorlink = |year = 2006|month = June] cite web|url =|title =Night restrictions at Heathrow, Gatwick and Stansted (second stage consultation)|accessdate = 2008-07-12|last = Dept for Transport|authorlink = |year = undated]


*C. Michael Hogan and Jorgen Ravnkilde, "Design of acoustical insulation for existing residences in the vicinity of San Jose Municipal Airport", January 1 1984, FAA grant funded research, ISBN B0007B2OG0
*"U.S. Noise Control Act of 1972" United States Code Citation: 42 U.S.C. 4901 to 4918
*S. Rosen and P. Olin, "Hearing loss and coronary heart disease, Archives of Otolaryngology", 82:236 (1965)

ee also

*Aviation and the environment
*Electric airplane
*Hush kit
*Hearing impairment
*Helicopter noise reduction
*Noise barrier
*Noise pollution
*Noise regulation

External links

* [ Federal Interagency Committee on Aviation Noise (FICAN)]
* [ Aviation Environment Federation (AEF)]
* [ Sound Initiative: A Coalition for Quieter Skies]
* [ A weekly newsletter on litigation, regulations, and technological developments]
* [ National Organization to Insure a Sound-controlled Environment(NOISE)]
* [ Attitudes to Noise from Aviation Sources in England (ANASE)] Study published by the United Kingdom Department for Transport

Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • No Aircraft Noise — No Aircraft Noise, or more fully The Common Cause No Aircraft Noise, was a minor Australian political party that operated from 1995 until 1999.[1] It was dedicated to removing noise pollution for residents of Sydney, which was generated by the… …   Wikipedia

  • Flight Track and Aircraft Noise Monitoring System — Fanomos (Flight Track and Aircraft Noise Monitoring System) ist ein wichtiges Werkzeug bei der Überwachung von Abflugstrecken (Minimum Noise Routings). Das System zeichnet die Spuren der Flugzeuge im Umfeld eines Flughafens auf. Mit seiner Hilfe… …   Deutsch Wikipedia

  • Noise mitigation — is a set of strategies to reduce noise pollution. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, and occupational noise control. Roadway noise and aircraft noise are the most pervasive… …   Wikipedia

  • 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,[1] other local and state… …   Wikipedia

  • Noise health effects — are the health consequences of elevated sound levels. Elevated workplace or other noise can cause hearing impairment, hypertension, ischemic heart disease, annoyance, sleep disturbance, and decreased school performance. Changes in the immune… …   Wikipedia

  • Noise pollution — A Boeing 747 400 passes close to houses shortly before landing at London Heathrow Airport Noise pollution is excessive, displeasing human, animal or machine created environmental noise that disrupts the activity or balance of human or animal life …   Wikipedia

  • aircraft — noun ADJECTIVE ▪ fixed wing, jet, light, low flying, supersonic ▪ Three men were flying in a light aircraft at low altitude when a passenger jet approached. ▪ attacks by helicopters and fixed wing aircraft …   Collocations dictionary

  • Noise Control Act — The Noise Pollution and Abatement Act of 1972 is a statute of the United States initiating a federal program of regulating noise pollution with the intent of protecting human health and minimizing annoyance of noise to the general public.[1] The… …   Wikipedia

  • Aircraft — An aircraft is a vehicle which is able to fly through the Earth s atmosphere or through any other atmosphere. Rocket vehicles are not aircraft if they are not supported by the surrounding air. All the human activity which surrounds aircraft is… …   Wikipedia

  • noise — noise1 W2S2 [nɔız] n [Date: 1200 1300; : Old French; Origin: quarreling, noise , from Latin nausea; NAUSEA] 1.) [U and C] a sound, especially one that is loud, unpleasant, or frightening = ↑sound ▪ What s that noise? noise of …   Dictionary of contemporary English

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”