Kiera Jefferson
Aircraft noise pollution is a significant issue that has been associated with several adverse health effects, from sleep disorders to cardiovascular disease. Aircraft engines are the major source of noise, often exceeding 140 decibels during takeoff. The noise produced by aircraft in flight can cause community annoyance, negatively impact children's academic performance, and increase the risk of cardiovascular disease for those living near airports. Large-scale studies have found exposure-response associations between aircraft noise and poorer reading comprehension and recognition memory in children. Aircraft noise is defined as unwanted sound and can impact human health and well-being, causing annoyance, discomfort, and interference with thoughts and activities. With the reorganisation of UK airspace, the concentration of flights over specific communities and the resulting noise pollution have become a public health concern.
| Characteristics | Values |
|---|---|
| Definition | "Unwanted sound" produced by aircraft in flight |
| Sources | Engine and other mechanical noise, aerodynamic noise, aircraft systems (cockpit, cabin pressurization, conditioning systems, auxiliary power units) |
| Health Effects | Sleep disorders, cardiovascular disorders, hearing impairment, hypertension, annoyance, decreased school performance, increased workplace accident rates, stimulation of aggression and other anti-social behaviors |
| Noise Stages | US FAA Stage 1 (Loudest) to Stage 4 (Quietest) for civil aircraft |
| Regulations | Governments have enacted controls for aircraft designers, manufacturers, and operators |
| Public Perception | Annoyance, displeasure, discomfort, dissatisfaction, or offense |
| Legal Aspects | Aviation is exempt from noise nuisance claims, resulting in limited legal protection for affected individuals |
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What You'll Learn
Aircraft noise sources
Aircraft noise pollution refers to noise produced by aircraft in flight that has been associated with several negative stress-mediated health effects, from sleep disorders to cardiovascular disorders. Engines are the main source of aircraft noise. Aircraft gas turbine engines (jet engines) are responsible for much of the aircraft noise during takeoff and climb, such as the buzzsaw noise generated when the fan blades reach supersonic speeds. Engine noise can exceed 140 decibels (dB) during takeoff.
The noise originates from three main sources: engine and other mechanical noise, aerodynamic noise, and noise from aircraft systems. The rotation of engine parts is most noticeable when fan blades reach supersonic speeds. Aerodynamic noise is caused by the airflow around the surfaces of the aircraft, especially when flying low at high speeds. Aircraft flying at low altitudes produce more noise due to air density. Low-flying, high-speed military aircraft produce especially loud aerodynamic noise.
Much of the noise in propeller aircraft comes from the propellers and aerodynamics. Helicopter noise is aerodynamically induced by the main and tail rotors and mechanically induced by 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.
Noise from aircraft systems—cockpit, cabin pressurization, conditioning systems, and Auxiliary Power Units (APUs)—also contributes to overall aircraft noise. The APU is an onboard generator used to start the main engines and provide electrical power while the aircraft is on the ground. Specialized electronic equipment in some military aircraft can also produce significant noise levels.
To address aircraft noise pollution, governments have enacted controls that apply to aircraft designers, manufacturers, and operators, resulting in improved procedures and reductions in pollution. Aircraft manufacturers are working on the design of supersonic civilian aircraft that produce a transient noise called a sonic boom. However, with advancements in noise reduction technologies, the airframe typically produces more noise during landing than takeoff.
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Health effects
Aircraft noise is defined as "unwanted sound", and it is one of the most detrimental environmental effects of aviation. Aircraft noise can affect human health and well-being in a variety of ways.
One of the most common adverse health effects associated with aviation noise is annoyance, which can be defined as a feeling of resentment, displeasure, discomfort, dissatisfaction, or offence when noise interferes with thoughts, feelings, or activities. Aircraft noise at high levels can also be considered a stressor on the body, activating the cardiovascular system and releasing stress hormones. Research has found an association between high levels of aircraft noise and an increased risk of developing cardiovascular disease (CVD). There is also evidence to suggest that cardiovascular effects are more strongly linked with night-time noise exposure.
Aircraft noise can also cause sleep disturbance, which can lead to next-day fatigue. A 2023 study found that aircraft noise, even as low as 45 dB, increased the risk of sleeping less than seven hours a night. This is particularly detrimental to children, as it can affect their cognitive performance, including attention, perception, mood, learning, and memory. The RANCH study, which examined 2844 children aged 9-10 years old from schools around London Heathrow, Amsterdam Schiphol, and Madrid Barajas airports, found exposure-response associations between aircraft noise and poorer reading comprehension and recognition memory.
Additionally, aircraft noise has been linked to an increased risk of hypertension, especially with high exposure during the night-time. A German study concluded that aircraft noise significantly impairs health, with a daytime average sound pressure level of 60 decibels increasing coronary heart disease by 61% in men and 80% in women. Similarly, a night-time average sound pressure level of 55 decibels increased the risk of heart attacks by 66% in men and 139% in women.
Overall, aircraft noise pollution can have significant health effects, including increased stress, sleep disturbances, and an increased risk of cardiovascular disease and hypertension. These impacts can vary depending on social, psychological, and economic factors, as well as housing structure and cultural values.
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Legislation and regulation
In the United States, aviation noise became a public issue in the 1960s, prompting the government to implement legislative controls. The Federal Aviation Administration (FAA) regulates the maximum noise level that individual civil aircraft can emit through noise certification standards. These standards are defined in the US Code of Federal Regulations (CFR) Title 14 Part 36 – Noise Standards: Aircraft Type and Airworthiness Certification (14 CFR Part 36). The FAA's noise certification standards have resulted in quieter aircraft, with older Stage 3 aircraft being upgraded to Stage 4.
In the United Kingdom, the government's policy on controlling aircraft noise falls under the remit of the Department for Transport (DfT). However, apart from Heathrow, Gatwick, and Stansted airports, where the DfT directly regulates aviation noise, the overall policy is that local authorities handle noise issues at a local level. This means that decisions about aircraft night-time operations and the number of aircraft allowed to fly daily are typically made by local authorities when approving the construction or expansion of an airport. The UK Civil Aviation Authority (CAA) has the final say on where aircraft are permitted to fly and must consider noise impact, safety, and airspace efficiency when deciding on proposed routes. The CAA's Airspace Regulation department determines whether changes can be made to airspace design and some air traffic control procedures, adhering to international standards, legislation, and government policy. The CAA's Chief Technical Noise Advisor (CTNA) provides specialist research and advice to the government and the CAA's Airspace Regulation team.
While aviation is generally exempt from noise nuisance claims, organisations like the Aviation Environment Federation (AEF) advocate for the introduction of quantitative noise limits and targets to protect health. The AEF also supports tougher noise standards for manufacturers and incentives to phase out old, noisy technology. In the UK, the Lowest Observed Adverse Effect Level (LOAEL) has been established as 51 dB LAeq,16h for an average summer day and 45 dB LAeq,8hr for an average summer night. This means that noise will be a significant factor in planning decisions and may lead to noise mitigation support.
To monitor noise levels, many airports employ aircraft noise monitors, sound level contour maps, and other equipment. These tools help airports and regulatory authorities assess noise impacts on specific locations and determine areas requiring noise mitigation.
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Aircraft noise and children
Aircraft noise pollution refers to the noise produced by aircraft in flight or on the ground, which has been associated with several negative health effects, from sleep disorders to cardiovascular disorders. Aircraft noise has been found to be particularly detrimental to children's health and cognitive development.
The RANCH study (Road traffic and Aircraft Noise and children’s Cognition & Health) examined the effects of aircraft noise on 2844 children aged 9–10 years from 89 schools around London Heathrow, Amsterdam Schiphol, and Madrid Barajas airports. The study found exposure-response associations between aircraft noise and poorer reading comprehension and recognition memory. Specifically, a 5 dB increase in aircraft noise exposure was associated with a 2-month delay in reading age in the UK and a 1-month delay in the Netherlands.
The Munich Airport study also found that high noise exposure was associated with poorer long-term memory and reading comprehension in children aged 10 years. These cognitive impairments were no longer present two years after the airport closed, suggesting that the effects of aircraft noise on cognitive performance may be reversible.
In addition to cognitive effects, aircraft noise has been found to negatively impact children's psychological health and quality of life. Studies have shown a significant decrease in total quality of life 18 months after aircraft noise exposure, as well as motivational deficits and parallel shifts in children's attributions for failure.
The health consequences of aircraft noise pollution have prompted governments to enact extensive controls on aircraft designers, manufacturers, and operators, resulting in improved procedures and reductions in pollution. However, more studies are needed to better define exposure-response relationships and the best noise metrics for health studies.
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Jet engines and propellers
Jet engines and aircraft components, such as propellers, produce noise pollution during various stages of flight, including taxiing, takeoff, climb, cruise, descent, and landing. Jet engines, in particular, are responsible for significant noise levels during takeoff and climb. Aircraft gas turbine engines, or jet engines, generate noise due to the high-velocity jet exiting the back of the engine, which creates an inherent shear layer instability if it is not thick enough. This instability causes the formation of ring vortices that subsequently break down into turbulence, resulting in noise. The noise associated with engine speed or the jet's speed is directly proportional to the noise level, so reducing exhaust velocity can significantly decrease jet noise.
Engine design plays a crucial role in noise levels. For example, the geared Pratt & Whitney PW1000G engine, which enables the fan to spin at a slower speed than the LP turbine, significantly reduces noise levels in several aircraft. Similarly, the PowerJet SaM146 engine in the Sukhoi Superjet 100 employs 3D aerodynamic fan blades and a specially designed nacelle to minimize noise. These advancements in engine technology have contributed to a notable decrease in noise levels over the years.
Propeller aircraft, including helicopters, also contribute to noise pollution through their rotating propellers and rotors cutting through the air. The noise generated by propellers depends on factors such as the size of the propellers and the velocity of the propeller tips. Additionally, much of the noise in propeller aircraft arises from aerodynamic factors, such as the airflow around the aircraft's fuselage, control surfaces, and blades. The shape of the aircraft's nose, windshield, or canopy can influence the sound produced.
To address the issue of noise pollution, governments and regulatory authorities have implemented stringent controls and standards for aircraft designers, manufacturers, and operators. These measures aim to improve procedures and reduce noise emissions. For instance, Stage 3 and Stage 4 standards have been established for large jet and turboprop aircraft to meet specific noise requirements. Furthermore, priority is given to noise reduction at the source, such as engine noise and aerodynamic noise, along with adjustments to takeoff and landing procedures. These efforts reflect a recognition of the harmful effects of aircraft noise on human health and well-being.
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Frequently asked questions
Aircraft noise pollution is the noise produced by an aircraft in flight or on the ground, which has been associated with several negative health effects.
Aircraft engines are the major source of noise, often exceeding 140 decibels during takeoff. Other sources include high-speed turbulence over the fuselage, the rotation of engine parts, airflow around the aircraft's surfaces, and aircraft systems like the cockpit, cabin pressurization, and conditioning units.
Aircraft noise can cause a range of health issues, including hearing impairment, hypertension, sleep disturbances, cardiovascular disease, and increased stress and anxiety. It can also impact children's cognitive performance, memory, and learning abilities.
Yes, governments have enacted controls that apply to aircraft designers, manufacturers, and operators, leading to improved procedures and reductions in noise pollution. The US, for example, has noise stages defined in the Code of Federal Regulations, with Stage 1 being the loudest and Stage 4 the quietest for civil aircraft.
Aircraft noise is often a key environmental concern for communities near airports or flight paths. It can cause annoyance, disrupt sleep, and negatively affect property values. In some cases, flight path changes or increased air traffic can lead to more concentrated noise exposure for certain communities, impacting their quality of life.
