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Turning Down the Volume on Airport Noise

Every morning at 6:30, residents of a historic district near the San Diego International Airport are presented with a wake-up greeting more reliable and piercing than a rooster's call at sunrise. The noise they hear is that of a screaming jet charging down the runway, signifying another day of steady departures.

"Most of the people who live there don't set their alarm clocks," Nyle Marmion says with a grin. "They don't need to."

Marmion's resum reflects the growing importance airport officials are placing on an issue typically called airport noise mitigation or noise abatement. Formerly the manager of San Diego International Airport's noise management office, Marmion was recently named manager of the airport's Quieter Home Program, which is administered by C&S Engineers Inc. and designed to provide sound insulation for homes affected by airport noise.

Though the events of Sept. 11 have pushed security to the forefront, most airport officials agree that noise mitigation will always be a major issue for airports. As the nation's population continues to grow, so does the volume of commercial and cargo-related air traffic. With residential and commercial development around airports and in flight corridors on the rise, airport officials are confronted with the task of reducing the noise produced by aircraft during takeoffs and landings and while flying over populated areas.

"The main challenge (for airport officials) is running a safe and efficient operation while impacting the least number of people with noise," says Embry-Riddle graduate Michael Fay (BS, Professional Aeronautics, 1988), a management analyst at McCarran International Airport in Las Vegas. "Airport noise is a community issue. People who live near the airport have to deal with it every day."

And airports can't ignore them. Any major construction project by an airport requires environmental impact studies, including mitigation plans, according to Seth Young, professor of business administration at Embry-Riddle. "It only takes six months to build a new airport runway," he says, "but it can take six years to get started."

Hush kits

The airport noise issue was improved at the start of the new millennium when Stage 2 civil turbojet aircraft weighing more than 75,000 pounds were required by the FAA to comply with Stage 3 noise levels. Airlines equipped Stage 2 aircraft with "hush kits" or new engines, or retired them from service in favor of new airplanes that meet Stage 3 requirements.

There are still Stage 2 airplanes flying today, such as F-28s, 727s, and 737s, says Embry-Riddle graduate Stan Shepherd (BS, Aviation Business Administration, 1988), community program manager at Seattle-Tacoma International Airport. However, "since Sept. 11, several airlines have taken the older planes out of their fleet."

Today, major airports have noise abatemant plans to reduce aircraft noise and noise remedy programs to significantly decrease aircraft noise heard in homes and schools. Many airports participate in a voluntary Federal Aviation Regulation Part 150 noise study, which identifies existing noise levels and projects future noise levels, evaluates noise abatement and land use alternatives, and recommends programs designed to reduce the number of people affected by aircraft noise.

Upon completion of the Part 150 study, and FAA approval, airports may implement Part 150 recommendations and apply for federal funds that can be applied to the sound insulation of homes greatly impacted by aircraft noise.

Seattle-Tacoma International Airport completed its latest Part 150 study and submitted it to the FAA last December. Upon approval after a 180-day review process, the airport can start implementing Part 150-related plans, which includes its Fly Quiet Programs, designed to reduce aircraft noise levels.

One project, Shepherd says, studies takeoff and landing procedures to determine if certain carriers are making more noise than others. The airport also has created the Fly Quiet Committee - composed of citizens, planners, and other officials - to generate community involvement.

In another measure by the airport, airlines are not permitted to use engine power to back away from gates. Instead, aircraft are pushed away from gates by tugs. The airport also has restrictions on engine maintenance run-ups, which must be performed in one of four approved locations and are limited to two minutes during nighttime hours.

Though it is not an FAA requirement, some airports institute voluntary nighttime limits on flights. FAA studies have determined that the noise generated from one aircraft between 10 p.m. and 7 a.m. is equal to 10 aircraft in daytime hours. At San Diego International Airport, Stage 2 aircraft can depart from 7 a.m. to 10 p.m. and Stage 3 from 6:30 a.m. to 11:30 p.m. Arrivals are permitted 24 hours a day.

"Obviously, aircraft noise is more evident at night, because there is less life-related activity such as automobile and pedestrian traffic," Marmion says. "Of course, cargo-related companies like FedEx and UPS make most of their flights at night, so airports with a strong cargo presence are active 24 hours."

Paths of least resistance

Airport officials are working with the FAA to increasingly use flight paths that pass over industrial corridors, but due to residential development around airports nationwide there is often no alternative to flying above neighborhoods.

"If you looked at aerial photos of airports 30 or 40 years ago and compared them to aerial photos of the same airports today, you would see a vastly different picture," Fay says.

"In an ideal world, airports would be surrounded by industrial and commercial development instead of houses," he adds. "Though they try to work with municipalities to achieve compatible land use planning, airport officials are often confronted with residential development around the airport and in flight paths."

Weather conditions, geographical features and airspace from nearby airports are other factors that can leave airport officials with no alternative but to fly over neighborhoods. At McCarran, in Las Vegas, options to avoid departure routes over residential areas are often limited because of the region's mountainous terrain and the location of Nellis Air Force Base and other local airports.

"The lack of mountainous terrain to the east makes it attractive to take off in that direction," Fay explains. "However, because of growing residential development in the east, we have worked with the FAA to have flights depart to the west when air traffic and weather conditions permit.

"In cases of extreme heat, departures are permitted to the east (because of density altitude problems to the west)," he adds. "When the temperature is 100 degrees and above, the easterly runway is used."

Insulation or relocation

After an airport's Part 150 study is approved, it can apply for federal funds for projects such as the sound insulation of homes affected by aircraft noise and the acquisition of property for noise abatement and development initiatives.

Sound insulation is funded by a matching grant - 80 percent provided by the FAA and the remaining 20 percent by the municipality. Homeowners are not charged for the improvements, but in most cases are required to sign an easement that prevents them from suing the local municipality or the FAA regarding aircraft operations, including noise.

"Most homes will see an improvement of five decibels or more in noise reduction," says Embry-Riddle graduate Michael Hotaling (BS, Aircraft Engineering Technology, 1990), national director of the Quieter Home Program. His company, C&S Engineers, is insulating homes for seven airports, including Detroit, Cleveland, Pittsburgh, and San Diego.

"If noise is reduced by 10 decibels, it is perceived by the ears as being half as loud," he says. "That can result in a dramatic improvement in a person's quality of life."

When a new runway is needed and the airport does not have the land to expand, it has no choice but to acquire homes and relocate the homeowners. For noise abatement projects, it is better to offer sound insulation to homeowners in high-noise areas, Hotaling believes.

"Some people have an emotional attachment to their home and don't want to leave," Hotaling says. "Maybe they raised a family in the house and have a lot of memories there.

"Having their home sound-insulated allows them to remain where they want to be," he adds. "Of course, they still have to deal with the noise when they step outside."

When residents of a low-income neighborhood near Louisville International Airport complained they couldn't afford to relocate with the money they'd be paid for their homes, officials got innovative, says Robin Sobotta, assistant professor and director of the global management program at Embry-Riddle's Prescott, Ariz., campus.

"With grant money from the FAA, the state, and airport tenant fees, the airport created a new community seven miles away," she says. Ninety percent, or 750, of the residents happily moved.

-- Jeff Louderback

Designing Quieter Aircraft
Howard Patrick, professor of aerospace engineering at Embry-Riddle, has designed a three-bladed propeller for general aviation airplanes that is quieter than the more common two-blade prop. Support for his research came from the Advanced General Aviation Transport Experiment, funded by FAA, NASA, and industry.
The propeller is being fabricated by Global Aircraft Corp. and will be certified and marketed in the next two years. In the process, he developed and published the industry's first acoustic scaling laws for propeller noise.
After perfecting his propeller, Patrick has been working on designs for quieter aircraft exhaust systems. Also on the drawing board is a planned collaboration with Richard Felton, who recently retired from the aerospace engineering faculty at the Prescott, Ariz., campus. The two will develop a center for general aviation noise reduction in Prescott, not far from the Grand Canyon, where Congress wants to safeguard "natural quiet" from the overhead racket caused by sightseeing flights.