In 1989, the Airport Authority established an Aircraft Noise Abatement Committee (ANAC) and adopted an Aircraft Noise Abatement Policy. The policy calls for monitoring noise abatement strategies, land-use planning and aircraft operating procedures to minimize the impact of aircraft noise.
The Noise Abatement Program Includes:
Establishment of a noise office, where an Airport Authority staff member assists the public with questions or concerns about aircraft noise. Citizens may call the Noise Office at (919) 840-2100.
Air Traffic Control procedural changes to clear departing aircraft directly to an altitude of 7,000 feet and to hold inbound aircraft at a higher altitude of 8,000 feet until they pass over the departing aircraft.
Future use of noise monitors to measure the impact of aircraft noise on various parts of the community.
Publication of noise-contour and flight track maps periodically to inform citizens of predominant jet departure and landing paths. The maps include contours that show aircraft noise exposure levels over an average annual 24-hour period, and the contours when all operations are in one direction for an entire day.
Adoption of a noise rule in 1990 that capped the allowable noise impact by limiting the total sound energy produced by airlines serving RDU. Air carriers operating above a minimum threshold of noise were allotted a noise “budget” that was reduced through 2004. In 2004, the allowable noise impact was 35 percent of the 1991 level.
Notification to property owners within areas of noise contours of requirement for noise disclosure when selling residential dwellings.
How Did RDU'S Noise Rule Work?
Passenger and cargo airlines operated within sound energy budgets set by the Authority's Noise Rule. The rule capped allowable noise in 1991 and reduced the noise budget of each carrier until 2004. Aircraft noise impacts are now equal to pre-hub 1987 levels. By 2004, the total allowable noise exposure was 35 percent of the 1991 level.
Although the number of flights may increase, the total amount of aircraft noise can decrease. This is primarily accomplished by using quieter types of aircraft at RDU. To discourage late night and early morning flights, operations between 10 p.m. and 7 a.m. carried a greater charge against the noise budget.
Minimizing Aircraft Noise
While many factors determine how aircraft noise affects us, the jet engine is the single most significant point at which noise can be minimized. That is why in 1969 the Federal Aviation Administration adopted regulations requiring commercial jets to meet noise standards.
The FAA rules established three categories for jet aircraft. Stage 1 jets, such as the original Boeing 707s and McDonnell-Douglas DC-8s, are the oldest and noisiest aircraft. They have either been retired from service or retrofitted to meet quieter Stage 3 standards. Stage 2 jets, such as 727s, 737-200s and DC-9s are noisy aircraft. They have either been retired from service or retrofitted to meet quieter Stage 3 standards. Stage 3 jets such as 737-700s, 757s, A319s, Fokker 100s and regional jets are the quietest jets flying today.
By 2004, all commercial aircraft operating in the United States met the standards for Stage 3, the quietest category for jet aircraft.
Aircraft noise is most apparent during jet takeoffs and landings. Takeoffs produce noise when exhaust gases mix with cooler air outside the engine. The large fan-jet engines in modern Stage 3 aircraft muffle the noise by reducing the speed of exhaust. In landing, jet engines emit a hissing sound created when pilots reduce power to slow down. This sound has been diminished in Stage 3 aircraft in several ways, including lowering the speed of the fans and installing sound-absorbing material in the engine.
In 2004, 99.9 percent of the jets operating at Raleigh-Durham International Airport were Stage 3 aircraft. This proportion has more than doubled since 1989 because of the phase-out of noisier planes.
The Noise Rule, which took effect in 1991, encouraged the use of quieter aircraft by annually reducing the noise budget allotted to carriers serving RDU through 2004.
Congress is currently considering adoption of a law that would require all business jets to meet Stage 3 noise standards. Although business jets are not required to meet Stage 3 noise standards, most business jets operating at RDU do so.
Although engines are the primary source of aircraft noise, a variety of other factors influence our perception of noise.
Proximity - A plane is noisiest when it is in closer range.
Weather - In bad weather, engine noise may reflect off thermal layers in the atmosphere, making jets sound louder than on clear days.
Air traffic controllers will direct pilots around storms. This may take planes over areas not normally affected by aircraft noise.
Routes - Much of the airspace south of RDU is made up of federally restricted Military Operational Areas. This limits the routes open to southbound non-military aircraft.
Non-scheduled operations - Military and private jets and helicopters were not subject to RDU's Noise Rule.
Emergencies - An emergency may prevent an airplane from landing, requiring the pilot to make an additional approach to the airport.
Weight - A heavy load may affect an aircraft's rate of ascent.
For More Information
For more information about RDU's Noise Abatement Program, call the Noise Office at (919) 840-2100.