Charlotte Douglas International Airport is updating its noise exposure maps for the first time since 1998, and the new maps could lead to more homeowners being bought out or receiving noise insulation.
The starfish-shaped noise exposure maps help city officials determine which properties are eligible for purchase by Charlotte Douglas and which are eligible for extra insulation, storm doors and storm windows, based on the average amount of noise they receive from jets overhead.
Charlotte Douglas has hired consultant Landrum & Brown, and plans to finish the project by July 2015, with maps for now and looking ahead to 2020. It’s too soon to predict how much the airport’s noise boundaries will shift, officials say.
“We don’t know what that will look like until we run the program,” said deputy interim Aviation Director Jack Christine. “This map will tell us what areas are eligible for noise mitigation.”
As Charlotte Douglas has grown, its noise has increased along with the number of flights. With more than 700 daily departures, Charlotte Douglas is the sixth-busiest airport in the nation.
The loudest airport noise is north and south of the airport’s three parallel runways and off the ends of its diagonal runway, where planes fly low during takeoff and landing.
To identify noise problem areas, Landrum & Brown is developing a detailed computer model of daily flights at the airport and their attendant noise. The model’s predictions are then checked against decibel measurements from around the airport to ensure accuracy.
Airplane sounds are measured during the day and night and averaged together, with a 10-decibel penalty added to noise between 10 p.m. and 6 a.m. Areas with an average of 65 decibels of noise or more are considered unsuitable for houses, schools, places of worship, nursing homes, libraries, hospitals and other similar uses.
The averaging of noise levels means that even though a house might have several flights a day that exceed the 65 decibel threshold, the property might not qualify for noise insulation if the average is under 65 decibels.
Charlotte Douglas has bought out neighborhoods in the path of planes, a process that generally takes years. The former Morris Park neighborhood north of Wilkinson Boulevard has been demolished since the airport acquired almost all of the property there, and is now an airport employee parking lot and future rental car maintenance facility.
So far, Charlotte Douglas has insulated about 1,000 homes, six churches and three schools against airplane noise. About 400 properties in the highest-noise areas have been purchased. Most of the $67 million worth of expenses has been reimbursed by the federal government.
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