Fri 18 Jan 2008 - The Partnership for AiR Transportation Noise and Emissions Reduction (PARTNER), a leading US aviation cooperative research organization headquartered at the Massachusetts Institute of Technology (MIT), has released two studies over the past month. The first provides new information for ensuring that communities in proximity to airports are minimally affected by aviation-generated low-frequency noise (LFN) and the other released the results of a three-year study of land use and noise complaint patterns at selected airports.
Aircraft emit low-frequency noise during takeoffs and when engine thrust reversers are used to slow landings. Since low-frequency sound encounters less absorption than higher frequency sound as it travels through the air, it persists for longer distances. Residents close to airports perceive low-frequency noise as a distant rumbling sound, structural vibration or by objects rattling in their homes.
Some of the major findings of the LFN research study are:
· Start-of-takeoff-roll, runway acceleration and thrust reversal generate high LFN levels (below 200Hz) at critical distances from runways (around 3,000 feet in the study).
· Assessment of impact should include multiple events in areas where noise from multiple runways can impact a neighbourhood simultaneously.
· People are responding to a broad range of noise levels; predictions must consider the full array of frequencies. Means of predicting potential loudness should include frequency content below 50Hz to optimally correlate with the perception of LFN.
· The risk of window glass rattle is lowered when windows are specifically designed to avoid resonating due to noise. Outdoor-indoor transmission glass rating is preferable for rattle-prone situations than the sound transmission class commonly used in rating windows.
The study presents numerous technical recommendations for metrics that planners may now use in calculating potential LFN impacts on local communities.
The work was funded by the Federal Aviation Administration’s (FAA) Office of Environment and Energy in response to a Congressional request.
Also funded by the FAA, the second study, Land Use Management and Airport Controls: Trends and indicators of incompatible land use, was an effort to better understand the dynamics of land use management, public concerns and air traffic-related annoyance.
The research found that a disproportionate number of complaints come from a few households. The results also suggest that in the US the size of a population tends to increase near airports. Data indicated a pattern where construction of housing units occurs at a rate higher than for the surrounding county, particularly for the first few decades of an airport’s operation. This indicates, recommends the study, the necessity of having appropriate zoning ordinances in place early in an airport’s development process to limit, or prohibit, the construction of residential units in incompatible locations.
Three major US airports were examined and it was noted that each had noise abatement strategies but that these procedures were not always followed.
Results also suggest that additional research using psychoacoustic assessments of noise complaint populations, critical assessment of land use decisions, a more in-depth look at aircraft noise levels and characteristics, and the dynamics and drivers of public concerns would be beneficial to more effectively manage noise and land use issues.
The PARTNER research organization is an FAA Center of Excellence sponsored by the FAA, NASA and Transport Canada. Its other aviation environmental impact projects are examining emissions, alternative fuels and other noise issues.
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