Measuring Airport Noise: Decibels, Sensors, And Impact

Airport noise levels are a major concern for local communities, and their impact on people's health and quality of life cannot be understated. The way aircraft noise is measured is complex and involves using different metrics like LAeq, Lden, and SEL, each with its own advantages and limitations. The most common measure of noise is the A-weighted sound level, known as dBA. However, noise is not just about decibels; the pitch, vibration, variation in intensity, and length of exposure time can also have impacts. For example, studies indicate that singular event metrics provide a more accurate forecast of sleep disturbance compared to extended average noise metrics.

Decibel metrics: Lmax, Leq16h, and SEL

Airport noise levels are typically measured using decibel metrics, which account for the varying responses of the human ear to different sound frequencies and intensities. Three key decibel metrics used in this context are Lmax, Leq16h, and SEL.

Lmax measures the loudest part of a flight. It captures the highest time-weighted sound level measured over a given period, with the term indicating the frequency weighting and time constant used. For instance, Fast Max (LAFmax) and Slow Max (LASmax) refer to different time constants.

Leq16h describes the cumulative noise exposure from aircraft noise events over a 16-hour period, typically from 0700 to 2300, which is the UK's official description of daytime. This metric is significant as research has found a correlation between annoyance due to aircraft noise and this cumulative measure.

SEL, or Sound Exposure Level, is a measure of the total energy of a sound event. It is calculated by taking the A-weighted sound pressure levels, squaring them to obtain the sound power, summing this power to account for the energy, and then using a reference pressure to scale the result logarithmically. SEL is valuable for environmental noise monitoring and regulatory compliance, especially in airport noise management, where it helps quantify the noise impact of aircraft takeoffs and landings on surrounding areas. It is also useful in urban planning for evaluating the effects of traffic noise and developing mitigation strategies. SEL simplifies the comparison of acoustic events by normalizing them to a standard duration of one second, regardless of the actual event's length.

Noise contour maps

The process of creating noise contour maps is a collaborative effort, often involving local governments, technical staff, and relevant authorities. For instance, the Metropolitan Washington Airports Authority (MWAA) developed noise projections and contours for Ronald Reagan Washington National Airport, in collaboration with the Federal Aviation Administration's Integrated Noise Model. This model considers information such as flight paths, runway usage, aircraft procedures, and the average number of daily operations by aircraft type and time of day.

The UK's Civil Aviation Authority (CAA) uses the ANCON model to generate noise contours for major airports, taking into account aircraft movement, noise generation, and sound propagation data. This model helps to create a comprehensive understanding of noise exposure in the areas surrounding airports.

The interpretation of noise contour maps can vary, and communities near airports may have different perspectives on the impact of noise pollution. Some may consider the number of flights per day by heavy cargo jets, while others may focus on frequent flights by smaller aircraft. Ultimately, the understanding of noise pollution and the implementation of noise abatement measures are influenced by the specific context and priorities of each community.

Impact on individuals

The impact of airport noise on individuals is a complex issue that depends on several factors, including the length of exposure, personal sensitivity, and the individual's activity at the time of the noise occurrence. Aircraft noise is considered one of the most detrimental environmental effects of aviation, and it can have significant impacts on people living in airport vicinities.

One of the primary ways airport noise affects individuals is by causing sleep disturbances. Studies have shown that noise above 55 dB Lnight poses a significant concern to public health, with levels above 45 dB Lnight increasing the risk of hypertension and associated issues like strokes and dementia. Aircraft noise can also lead to increased levels of annoyance and stress, with individuals near airports reporting higher annoyance levels due to airplane noise compared to other sources such as urban rail transit or high-speed railways.

The level of annoyance caused by airport noise can vary based on several factors. These include the duration of exposure, with longer exposure times potentially leading to increased annoyance. Personal sensitivity also plays a role, as some individuals may be more affected by noise than others. The impact of outside influences, such as background noise or local environment, can amplify or reduce the annoyance caused by airport noise. Additionally, an individual's activity at the time of noise occurrence matters; for example, noise during sleep or while engaging in activities that require concentration can be more disruptive.

Airport noise can also have indirect effects on individuals by influencing land use and property values. Measures to mitigate airport noise may involve restricting how land is used near airports, which can impact individuals' residential or business locations. Some states include the monetization of noise in their policymaking, taking into account individuals' willingness to pay to avoid noise exposure. This can result in variations in property values and the cost of living in areas near airports.

Overall, the impact of airport noise on individuals is a multifaceted issue that goes beyond mere decibel levels. It involves understanding the human reaction to noise, including annoyance, stress, and sleep disturbance, and considering the varying responses based on individual factors and circumstances. By recognizing these impacts, communities and authorities can work together to implement effective noise reduction and mitigation strategies to minimize the disturbance on local neighbourhoods and individuals.

Pitch, vibration, and intensity

While noise level measurements often focus on decibels, other factors such as pitch, vibration, and intensity also play a crucial role in understanding the impact of noise pollution, especially in communities near airports.

Pitch refers to the highness or lowness of a sound, and different types of aircraft produce varying pitches of sound. For instance, the sound of a heavy cargo jet taking off or landing may have a different pitch compared to a smaller, single-engine aircraft. The pitch of a sound can affect how it is perceived and tolerated by individuals, with some pitches being more annoying or intrusive than others.

Vibration is another important aspect of noise pollution. Aircraft engines, particularly during take-off and landing, can create significant vibrations that contribute to the overall noise impact. These vibrations can be felt as well as heard, adding another layer of disturbance for those living near airports. Vibration can also affect the structural integrity of buildings and other infrastructure over time.

Intensity, often measured in decibels (dB), indicates the loudness or strength of a sound. It is a crucial factor in determining the potential for sleep disruption and noise annoyance. The decibel scale is logarithmic and relates sound intensity to the smallest audible sound of 0dB. For example, a sound 10 times more powerful than the threshold of hearing is 10dB, while a sound 100 times more powerful is 20dB. The A-weighted sound level, known as dBA, is commonly used to measure noise levels, taking into account both intensity and frequency.

Different metrics are used to assess noise pollution, including LAeq, which represents the average sound level over a specified period, and SEL (Sound Exposure Level), which quantifies the sound exposure level of an aircraft occurrence in dB through a one-second continuous noise burst. Noise contour maps are also employed to identify areas with significant noise pollution and guide airport development and noise mitigation plans.

Noise abatement measures

• Recommended Procedures: Organizations like the National Business Aviation Association (NBAA) provide recommended noise abatement departure and arrival procedures for pilots and aircraft operators. These procedures are designed to be suitable for any aircraft type and airport environment, ensuring consistent and effective noise reduction. NBAA's Noise Abatement Program has been in place since 1967.
• Airport-Specific Initiatives: Individual airports often implement their own noise abatement programs. For example, Van Nuys Airport in Southern California has a Quieter Nights Program that encourages turbine operators to reduce noise during nighttime operations. Similarly, Toronto Pearson International Airport has published a guide with recommended operating techniques and arrival procedures to minimize noise.
• Noise Monitoring and Modeling: Airports employ noise monitoring systems, such as the Airport Noise and Operations Monitoring System (ANOMS), which utilize fixed noise monitors placed around the airport to measure and track noise levels. This data is crucial for identifying noise hotspots and evaluating the effectiveness of noise abatement measures. Additionally, computer models like the Integrated Noise Model (INM) are used to predict and assess aircraft noise exposure over geographic areas, aiding in decision-making.
• Regulatory Compliance: The Federal Aviation Administration (FAA) in the United States plays a significant role in regulating noise levels. They set maximum noise standards for aircraft, requiring them to meet specific noise certification standards. The FAA also offers federal funding for approved noise mitigation projects around airports through their Part 150 program, which includes noise abatement procedures and land-use control measures.
• Noise Insulation: In some cases, localities opt for noise insulation strategies, such as home insulation, to reduce noise exposure for individuals living near airports. While this approach can be costly and less effective than reducing noise at the source, it may be necessary when further source mitigation is not feasible.
• Community Engagement: Airports often work closely with local communities to address noise concerns. This includes providing noise complaint hotlines, responding to citizen inquiries, and collaborating with aircraft operators and air traffic control to find solutions that balance operational needs with community well-being.
• Flight Pattern Adjustments: Adjusting flight patterns can effectively reduce noise exposure for those on the ground. Changes to arrival and departure routes, as well as flight scheduling, can distribute noise impact more evenly and avoid concentrating it in specific areas.

By implementing these noise abatement measures, airports can actively work towards reducing the impact of aircraft noise on nearby communities, improving the quality of life for residents, and fostering better relationships with their neighbors.

Frequently asked questions