Aircraft Noise

Measuring Noise

The Federal government has adopted a method to measure noise, called the day-night level (DNL), to determine if a community is eligible for Federal grants to reduce the impacts of aircraft noise.

DNL is the average noise exposure level over the course of a year. Nighttime noise is weighted more heavily than daytime noise to reflect its proportionately greater impact.

As a point of reference, experts note that the typical noise level in a metropolitan area is about 55 DNL.

Under current policies, areas within a 65 DNL contour may qualify for federal funds to minimize the effects of aircraft noise.

The Weather

Just about everything an aircraft does, including the noise it makes, is affected by the weather. Aircraft climb more slowly in warm weather, making operations louder on the ground. On cloudy days, the noise from aircraft rebounds down to the earth’s surface from the bottom of the clouds, making it louder. On windy days, aircraft noise carries farther at ground level too.

Wind is a major factor in how the tower controls takeoffs and landings. Aircraft are more stable when they take off or land into the wind. Prevailing winds in Louisville tend to come from the south, which supports the airport’s preferred daytime pattern of landings from the north and takeoffs to the south. However, about one day in five, winds will come from the north, requiring the pattern to be reversed.

In addition to surface-and upper-air wind speed, other factors like visibility, pavement conditions, precipitation and unusual atmospheric conditions (wind shear and microbursts) may affect which runway and direction are used.

Louisville International Airport (SDF)

The Airport Authority is responsible for operating the airport safely and efficiently with the least noise impact possible. The LRAA works with the FAA, airlines, airport users and neighbors to identify feasible and affordable solutions to community noise problems.

The Community Noise Forum plays a crucial role in this planning. Through the forum, the Airport Authority, the airlines, the FAA and the airport’s neighbors, a number of steps have been taken to minimize the impact of aircraft noise on residential areas.

Where noise has exceeded the Federal threshold, the airport has established a Voluntary Residential Relocation program and a sound-insulation program, called the Quieter Home® Program

Operations at Louisville International Airport (SDF)

SDF

The goal of the Airport Authority is to concentrate aircraft operations over the least populated areas, exposing the fewest people to aircraft noise levels incompatible with residential living. With the FAA’s approval, several changes in air traffic procedures have been made and include:

Departing aircraft

  • Take off to the south (weather permitting) to direct the noisiest operations away from the more densely populated areas north of the airport.
  • Maintain prescribed headings until they reach a specified distance from the airport. This ensures safe separation between aircraft, avoids restricted airspace to the south and minimizes noise exposure in neighborhoods near the airport.

Arriving aircraft

  • The normal daytime runway preference is for aircraft to arrive from the north. On weekdays, this preference is changed to the south for a short time, as there are significantly more arrivals than departures between 9:30 a.m. and 12:20 p.m. (approximately 2 to 1). This minimizes the number of flights over areas north of the airport.
  • Most aircraft now intercept the glide slope at higher altitudes.

Contraflow

  • A “contraflow“ pattern is implemented at night (10 p.m. to 7 a.m.) so that if weather permits, aircraft arrive from the south for a specified time, and then depart to the south for the remaining portion. This keeps noise south of the airport and over less populated areas.

Other Measures

  • Jet engine tests and run-ups of more than one minute are restricted to designated areas. Run-ups between 9 p.m. and 7 a.m. require prior approval.
  • The Airport Authority has a state-of-the-art flight tracking system that uses a unique “multi-lateration” process for tracking aircraft operations at Louisville International Airport and Bowman Field. The tracking system allows users to track flights and identify aircraft in near real-time or re-play mode. Visit this link for near-live flight tracks display system for Louisville International and Bowman Field.

Operations at Bowman Field (LOU)

The Louisville Regional Airport Authority is committed to being a good neighbor to those living around Bowman Field. It has asked the Air Traffic Control Tower to use a standard left-hand traffic pattern and available runways (based on wind and weather conditions) to minimize noise for all areas around the airport.

Safety Is Paramount

Noise Abatement Measures

(Not Intended To Take Precedence Over ATC Instructions)

  • Operate aircraft in such a manner as to cause the least noise, vibration and exhaust emission consistent with safety and efficiency.
  • Operate no aircraft with a maximum landing weight in excess of 30,000 pounds without approval of the Executive Director.
  • Conduct practice, training and/or proficiency operations between 7 a.m. and 10 p.m. and only if the Air Traffic Control Tower is in operation.
  • Conduct engine run-ups between the hours of 9 a.m. and 8 p.m.
  • Conduct run-ups in a manner that directs noise towards the center of the airport.
  • Use Aircraft Owners and Pilots Association or Manufacturer’s suggested Noise Abatement Techniques.

How to get Involved

The Community Noise Forum meetings are open to the public, and are normally held the fourth Monday of every other month at 6 p.m. at the LRAA’s Administration Building, 700 Administration Drive, just east of the passenger (departing flights) terminal. The next meeting is scheduled for Monday, July 28, 2014.

If you have questions or would like more information, or to confirm a meeting date, please contact the Airport Authority’s Noise Officer Bob Slattery (502) 363-8516 or E-mail Bob.Slattery@flylouisville.com