The definition of noise is unwanted sound, and noise from air traffic has a particularly detrimental impact on humans and the environment. Environmental noise can cause annoyance and anxiety, disrupt sleep, adversely impact learning abilities in children, and may increase the risk of cardiovascular disease in people living near an airport. In some communities, regulations to minimize the noise limit the growth of additional air traffic.
This aspect of air traffic noise refers to the disturbing effect that air traffic noise has on a community as a whole. The evaluation of a group of residents near an airport may be merged into a single outcome: annoyance. The negative effect on a community can be so great that the International Commission on Biological Effects of Noise proposed a standardized annoyance question to measure the impact. In practice, an evaluation using this question will produce a reliable indicator of total community annoyance. In addition, by using a standard question, the results may be compared to other evaluations around the globe.
The Exposure-Response Connection
With the growing recognition that noise can reach hazardous levels, scientists and community leaders have tried to connect the percentage of highly annoyed residents to differences in noise levels between day and night. The result was a variety of exposure-response curves from different environmental noise sources, such as railway, road traffic, and air traffic noise. Not surprisingly, air traffic noise had higher annoyance levels than road or railway traffic, even at the same exposure levels. Indeed, there is also evidence that community annoyance in response to air traffic is growing. The older exposure-response curves may no longer apply. The need for new measurements is significant as air traffic continues to expand.
The International vs. Local Exposure-Response Connection
The exposure-response connection applies primarily to long-term assessments of community annoyance response to air traffic. The data do not provide accurate insights into the short-term impact of changes in noise levels. For instance, the measurements may produce a skewed response in relation to the opening of a new runway. In more consistent environmental noise situations, the annoyance response can be quite different from the average expected response.
Because communities and airports differ in a broad array of variables, measuring community annoyance and comparing the results to surveys from around the world may produce more insights than simply predicting annoyance. Even so, the exposure-response connection is an important tool that enables communities to assess the health impact and set limits for aircraft noise.
Non-Acoustic Variables in Studies
A number of factors not related to environmental noise may play a part in the results in surveys to measure community annoyance. An individual who responds to the standardized question may have factors that exacerbate or mitigate their annoyance. These could be noise sensitivity, hearing loss, fear, age, coping mechanisms, trust in authorities, the belief that the source of the environmental noise is necessary, or previous experiences with high levels of noise.
Community Complaints about Air Traffic Noise
Airports receive complaints. In fact, complaints are so ubiquitous, many airports keep meticulous logs to record the reasons for the complaints. Their community outreach efforts use this information to tailor responses to their neighbors. Complaints can be triggered by extraordinary events (unusual aircraft that may be louder than normal) and operational changes (changes in flight schedules).
Annoyance is different than a complaint. Annoyance is personal, but taking the action to lodge a complaint has its basis in the annoyance. Very few studies have looked into the causative factors that lead to an actual complaint. Many studies look simply at the number of complaint calls rather than identify repeat callers. This different method of separating individual objections and callers may yield greater insights into ways to reduce the negative effects of environmental noise from air traffic. Another variable to consider is that complainants most likely do not accurately represent a cross-section of the community in either demographics or the nature of the annoyance.
Additional Environmental Noise Metrics
An important inquiry for determining the true impact of air traffic noise is to differentiate between frequent moderate noise levels versus infrequent high noise levels. Some studies have tried to measure this difference and weight some of the data. For instance, one study gave a higher weight to the total number of flights. However, the results have been inconclusive.
Environmental Noise Mitigation
Governmental leaders and other authorities generally agree that environmental noise from air traffic can be harmful and should be reduced. Many regulations regarding noise reduction address the source of the noise, such as aerodynamic noise or engine noise. They seek to mitigate the harmful effects with adjustments to take-off and landing procedures. However, these actions do not always produce sufficient reduction in noise levels. Many times, they are not feasible.
Some communities retrofit existing homes with insulation and noise-resistant windows. New homes built near an airport may be required to meet certain noise abatement standards. However, none of the regulations can address the individual factors that may exacerbate annoyance, such as noise sensitivity or trust in authorities. Developing communication strategies that tackle these issues could contribute to a reduction in annoyance levels, even if actual noise reduction has not happened
Substantial evidence exists that shows exposure to environmental noise from air traffic is related to higher annoyance indicators. Exposure-response connections add some accuracy to determining the level of annoyance within a community near an airport. Even so, several situational and personal factors play an important part in data. The most current evidence shows a need to update exposure-response curves that use individual factors to further refine the data. The result will be better information to base regulations upon. Better decision-making leads to better management of environmental noise from air traffic.