Part 2—Examples

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Index 1 2 3 Glossary

7. Overview

This section contains examples of transparent aircraft noise information that have been produced for some Australian airports. It is important that these be considered simply as examples and not be treated as the only way that aircraft noise can be described in a meaningful way. As indicated earlier, the prime purpose of this guidance material is to encourage new ideas and ways of describing aircraft noise, not to restrict them.

Most of the examples are presented in the form of printed graphical material. However, two examples—one based on sophisticated audio/visual presentations (Section 14) and the other on the Internet (Section 15)—are included to demonstrate that as technology evolves new avenues for portraying aircraft noise are appearing which go beyond printed graphics.

The printed graphics examples in this Part (Sections 8–13) have been generated by using either one or a combination of up to three distinct approaches. Information gathered by noise and flight path monitoring systems (NFPMS), supplemented by information from air traffic management systems, underpins most of the examples. Aircraft noise information which is computed rather than measured is sourced from the United States Federal Aviation Administration's Integrated Noise Model (INM). In most of the examples this base information has been manipulated using the DOTARS software, Transparent Noise Information Package (TNIP), to produce the final product.

The first two approaches—NFPMS and INM—involve complex hardware and software and consequently output data can only practically be obtained by using well-trained specialist personnel. On the other hand TNIP has been developed with a simple interface which is specifically designed to let the non-expert interrogate databases and produce high quality graphical output.

The applicability of the examples will vary from airport to airport. It is anticipated that each airport will select aircraft noise information to meet its own specific needs at any particular time. The type of information generated will depend to a large extent on what base data is available and/or the cost of gathering this data. This is discussed in Section 16.

Experience has shown that all aircraft noise information has strengths and weaknesses and is open to misinterpretation. A summary sheet precedes the following examples which comments on the strengths and weaknesses of each of the sample descriptors. Some of the key deficiencies can generally be overcome by using a combination of two or more of the charts.

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8. Flight path maps

Overview

Experience has shown that flight path maps are the basic aircraft noise information tool. Providing people with an indication of where aircraft fly effectively underpins all other aircraft noise information.

Examples of three different types of flight path map follow. These have been produced using the NFPMSs which are installed at major Australian airports.

Figure 8.1 A flight path map for one flight at Sydney Airport.

  • This type of map is ideal to give to a person making a complaint or query about one particular flight. It clearly shows where the aircraft went and also shows the height of the aircraft in the vicinity of the enquirer's home.

Figure 8.2 An enhanced flight path map for Brisbane Airport showing the heights of aircraft.

  • This type of map gives a good ‘macro’ picture of the typical spread of flight paths and is useful for showing someone that there is a natural variation in the location of flight paths around a core track
  • This map uses a colour coding system to give an indication of the heights of aircraft.
  • Flight path maps covering a period of a few hours are useful to show how the noise exposure patterns at an airport vary depending on which runways are being used.

Figure 8.3 A track density plot for Brisbane Airport.

  • Flight path maps for periods longer than a few days (for a busy airport) can tend to have too much information and present a confusing picture. Track density plots have been developed in order to synthesise this type of information and show the intensity of overflight activity for an extended period.

Figure 8.1 A flight path map for one flight at Sydney Airport

Departure of Eastern Airlines turbo prop aircraft on 18/7/99 at approx. 10.27. Lane Cove indicated.

Figure 8.2 An enhanced flight path map for Brisbane Airport showing the heights of aircraft

Track plots coloured by height for jet arrivals during the period 2/12/2002 to 8/12/2002.

Figure 8.3 A track density plot for Brisbane Airport

Track density plot for all aircraft operations during the 2002 calendar year.

Strengths

  • Flight path maps directly answer what is generally the first question asked about aircraft noise—where do the aircraft fly?
  • The maps are based on actual monitoring and do not rely on computer simulations.
  • The maps show that aircraft noise extends a long way from an airport and is not just confined to areas within an airport's noise contours.
  • The veracity of the information can be checked by observation although it is not as easy as it would appear to verify the accuracy of flight path maps by purely looking into the sky.

Weaknesses

  • Generic flight path maps do not provide a readily digestible ‘macro’ picture of the time distribution of overflights. That is, they do not normally contain information on the numbers of movements and the times at which they occurred.
  • Flight path maps can give the impression that aircraft will only be audible immediately under the flight path. They do not give direct info rmation on ‘noise’.
  • The maps are two dimensional and therefore, if colour coding is not used, they can give the impression that the altitude of an aircraft does not vary along the length of the flight path.

Suggested uses

  • responding to ‘one-off’ queries about a particular flight or flights over a short time period
  • input into noise assessment reports, for example, for airport consultative committees
  • environmental monitoring and reporting

Data source/software

  • NFPMS

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9. Flight path movement charts

Overview

Flight path movements charts were developed in consultation with the public to overcome some of the perceived weaknesses of flight path maps. They show a ‘macro’ picture of aircraft noise distribution around an airport.

In particular, the charts show that aircraft do not all follow the same track but tend to spread to generate distinct flight path zones. For many suburbs, aircraft overflight activity varies widely from day to day according to which runways are being used at the airport—runway use is primarily dictated by wind conditions. A flight path movements chart therefore contains, in addition to average day information, data on the busiest and quietest days during the period covered by the chart to give an indication of how noise varied over that period. Further details about flight path movements charts can be found in Chapter 2 of the DOTARS ‘Expanding Ways’ Discussion Paper (see Glossary).

Figure 9.1 A jet flight path movements chart for Perth Airport.

Strengths

  • Information on flight path location and aircraft movement numbers is combined in a way that is understandable to the non-expert.
  • Information is taken beyond the ‘average day’ by giving data on day-to-day variations.
  • The charts are based on ‘real’ data and not on computer modelling.
  • The information on the chart can be verified without special expertise or equipment, for example, by keeping a log of flight times.
  • The charts enable a rapid assessment to be made of the extent to which noise is shared between suburbs.

Weaknesses

  • The charts can give the impression that there are more movements in the wider flight path zones—this is not necessarily the case but the visual impression can override the information on the number of movements shown in the boxes on the charts.
  • Aircraft will still be heard outside the flight path zones.
  • The charts capture approximately 90 per cent of flights; ‘one-off’ flight paths are not shown on the charts for reasons of clarity—the charts are designed to only show a ‘macro’ picture for the main jet flight path routes.
  • The charts provide information on aircraft movements not aircraft noise.
  • Similar to the flight path maps, flight path movements charts are two dimensional and therefore they can give the impression that the altitude of an aircraft does not vary along the length of the flight path zone.

Suggested uses

  • providing information to prospective house purchasers about typical aircraft noise exposure patterns around an airport
  • responding to queries about trends in aircraft noise exposure
  • giving a picture of how noise is distributed between suburbs around an airport
  • input into EISs and noise assessment reports, for example for airport consultative committees
  • providing advice to supplement ANEF contours, for example for land use planners and decision-makers
  • environmental monitoring and reporting, both regular reporting and ‘State of the Environment’

Data source/software

  • NFPMS and TNIP

Figure 9.1 A jet flight path movement chart for Perth Airport

1 Jan 2001 to 31 Dec 2001 All jets. Total number of aircraft movements = 48,597.

Note: Track H includes all arrivals to Runway 03 from the east and all departures from Runway 21 to the east.
Track A is tracks B and C combined. Similarly, track F is track G and H combined.

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10. Respite charts

Overview

The respite chart gives an indication of the extent to which different areas around an airport get ‘breaks’ from aircraft noise. The monitoring and reporting of these ‘breaks’ or ‘respite’ was a special priority for Sydney residents following the opening of the new runway at Sydney Airport in 1994.

The charts report respite by showing the proportion of hours during which there were no jet aircraft movements on each of the flight paths. For example, if the respite on a particular flight path is reported as ‘50%’ it means that for 50 per cent of the clock hours during the period covered by the chart there were no movements on that flight path. A ‘clock hour’ means, for example, 8am to 9am. Further details about respite charts can be found in Chapter 3 of the DOTARS ‘Expanding Ways’ Discussion Paper (see Glossary).

Figure 10.1 A respite chart for Sydney Airport.

Strengths

  • The charts give information on what happens at ‘sensitive times’.
  • The information on the chart can be verified without special expertise or equipment, for example, by keeping a log of aircraft times.
  • The charts are based on ‘real’ information and not on computer modelling.

Weaknesses

  • The information on the charts describes respite for each individual flight path zone—in some cases respite on one track can be disturbed by movements on another track and therefore in these circumstances respite will be less than that reported.
  • On the other hand, the charts show respite based on one hour breaks—this is a very blunt instrument and means that an area can have zero respite yet get only 24 overflights a day.

Suggested uses

  • providing

information to prospective house purchasers about typical aircraft noise exposure patterns around an airport

  • responding to queries about trends in aircraft noise exposure
  • giving a picture of how noise is distributed between suburbs around an airport
  • providing information on what happens at sensitive times
  • input into EISs and noise assessment reports, for example for airport consultative committees
  • environmental monitoring and reporting, both regular reporting and ‘State of the Environment’

Data source/software

  • NFPMS and TNIP

Figure 10.1 A respite chart for Sydney Airport

1 Jan 2001 to 31 Dec 2001 All jets. Total number of aircraft movements = 156,069.

Note: Track A* is track B and C combined.

A respite hour is a whole clock hour (e.g. 06:00 to 07:00) when there are no jet movements.
Morning: 06:00 to 07:00 on week days. Daytime: 07:00 to 20:00 on week days.
Evening: 20:00 to 23:00 on week days. Weekend: 06:00 to 23:00 on weekdays .

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11. Single event contours

Overview

When people show an interest in gaining information on noise levels they rarely want to know about logarithmically averaged noise levels such as the ANEF. They are almost always interested in knowing about single event noise levels.

Single event noise data is generally either provided by showing computer generated ‘noise footprints’ or by providing data on the noise levels registered by individual flights at the noise monitors around airports.

In the past, single event contours have most commonly been shown as ‘straight in and straight out’ footprints on a plain background to show the noise differences between different aircraft types. These contours lack any contextual information and therefore have not provided an individual with information directly relevant to their home. The attached single event contour has been placed on a flight path superimposed on a satellite image for an area close to Sydney Airport. This approach, which allows a person to see ‘what it means for them’, has received very positive comments from users.

Figure 11.1 A single event contour for a B767 aircraft departing to the north-east from the third runway at Sydney Airport.

Strengths

  • The contours give a good indication of the sound pressure level at a person's home when an aircraft of a specified type operates on a specified flight path.
  • The information can be verified comparatively easily, for example, by the use of an inexpensive noise level meter.

Figure 11.1 A single event contour for a B767 aircraft departing to the north-east from the third runway at Sydney Airport

Weaknesses

  • The contour only relates to one flight path.
  • No information is provided on how often or at what time flights will occur on the flight path.
  • The contour only applies to one type of aircraft, and, if a departure, for one stage length—the noise a departing aircraft generates is very dependent on the distance to that aircraft's destination, that is on the amount of fuel being carried.
  • The contours are generated solely by computer modelling.

Suggested uses

  • responding to queries about the noise levels generated by individual aircraft
  • showing a comparative picture between operations by different types of aircraft, both between current aircraft and between old and new generation aircraft
  • input into EISs and noise assessment reports, for example, for airport consultative committees

Data source/software

  • INM and TNIP

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12. N70 contours

Overview

The use of N70 contours evolved out of community interest in single event contours. In essence, the N70 contour map summarises single event data for a specified time period over the area surrounding an airport and has proven to be a good way to produce a ‘whole of airport’ picture of single event aircraft noise patterns.

The noise contours on an N70 chart indicate the number of aircraft noise events louder than 70 dB(A) which occurred on the average day during the period covered by the chart. An aircraft noise event of 70 dB(A) is one that is likely to disturb conversation inside a house with open windows. This event therefore may interfere with activities like watching television or using the telephone. Further details about N70 contours can be found in Chapter 4 of the DOTARS ‘Expanding Ways’ Discussion Paper (see Glossary).

The term ‘N70’ has also commonly become used as a generic expression for the family of ‘Number Above’ descriptors. Contours showing the number of events above 60 dB(A) and 80 dB(A) are also frequently generated for specific applications—see the notes below for Figure 12.2.

Figure 12.1 An N70 contour for Canberra Airport.

Figure 12.2 An N60 contour for Bankstown Airport.

  • There is generally a significant difference between the aircraft noise environment in the vicinity of major jet (RPT) airports and that around General Aviation (GA) airports. At GA airports the community, particularly residents of areas under training circuits, are exposed to noise from much quieter aircraft but the number of overflights is often significantly greater. Therefore, while a level of 70 dB(A) has been adopted as an indicator for RPT airports, given that a level of 60 dB(A) is typical of the noise level of aircraft in training circuits around a GA airport, the N60 is considered to be a more appropriate descriptor for these airports.

Figure 12.1 An N70 contour for Canberra Airport

Figure 12.2 An N60 contour for Bankstown Airport

Strengths

  • N70s report noise by the number of single events which is the way a person generally experiences and perceives aircraft noise.
  • The contours are arithmetic—for example, all other things being equal, if the number of flights on a flight path doubles, the N70 doubles.
  • The information can be relatively easily verified, for example, by cross-comparing with a measured N70 chart.
  • N70s are useful for showing noise exposure in a meaningful way for short time periods, for example evening periods, as it takes information beyond the ‘average day’.

Weaknesses

  • Like any noise contour an N70 contour can give the impression that there is no noise beyond the outer contour.
  • Some people distrust the contours as they are produced using computer models and not by measurement.
  • It is not readily apparent what a sound pressure level of 70 dB(A) will be like in practice.

Suggested uses

  • giving a ‘macro’ picture of noise around an airport to complement and put into perspective information based on flight paths and movement numbers and times, etc
  • input into EISs and noise assessment reports, for example for airport consultative committees
  • providing advice to supplement ANEF contours, for example for land use planners and decision-makers
  • environmental monitoring and reporting, both regular reporting and ‘State of the Environment’

Data source/software

  • INM and TNIP

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13. Measured N70 charts

Overview

Despite the enormous efforts that have gone into verifying the output of computer models such as INM, members of the public tend to be very wary of computer modelled data and often have much more faith in data which has been recorded by an NFPMS. The measured N70 chart reports actual noise measurements made around an airport. This contrasts with N70 contours which are generated by computer modelling. The measured N70 not only provides information from a source that is more trusted by some people, it also provides a good tool for checking the accuracy of N70 contours.

At most major Australian airports, aircraft operations are monitored using an NFPMS. These systems gather large amounts of data and experience has shown that it is difficult to synthesise the results of the noise monitoring in a way that is meaningful. It has been found that a useful overview picture of aircraft noise monitoring data can be obtained by using the N70.

Figure 13.1 A measured N70 chart for Sydney Airport.

Strengths

  • The charts summarise a great deal of information in a way that is easy to comprehend.
  • The information is derived from noise monitoring not computer modelling.
  • The charts provide information on daily ranges in the N70 and also on noise exposure at sensitive times.
  • This form of representation allows a comparison to be made between computer generated N70 contours and measured N70 data.
  • Measured N70s allow a rapid overview examination to be made of the noise generated by particular operations or aircraft types, for example, departures by B747s.

Weaknesses

  • The charts only provide information for those locations at or very near to the noise monitoring terminals.
  • The information needs to be treated with caution since sound pressure levels can change rapidly even at a short distance from a noise-monitoring terminal—particularly for landings.
  • It is not readily apparent what a sound pressure level of 70 dB(A) will be like in practice.

Suggested uses

  • summarising the results of a period of noise monitoring
  • cross-checking N70 contours
  • input into EISs and noise assessment reports, for example, for airport consultative committees
  • environmental monitoring and reporting

Data source/software

  • NFPMS and TNIP

Figure 13.1 A Measured N70 chart for Sydney Airport

Morning: 0600: to 07:00. Daytime: 07:00 to 20:00. Evening: 20:00 to 23:00. Night: 23:00 to 06:00 (in the same day)

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14. Audio/visual presentations

Overview

A number of audio/visual products have been developed in recent years to demonstrate aircraft noise to non-expert audiences via the medium of public ‘noise simulation’ presentations. These products are capable of generating very high quality sound and visual images. Typically the audio/visual tools would be used as a part of the consultation process on a major airport project such as the construction of a new runway.

A public noise simulation session is likely to be convened by an expert facilitator who uses the product to demonstrate a wide range of noise effects and to respond to queries raised by the audience. The demonstrations are likely to include, for example, showing the differences in noise generated by different aircraft types, the changes in noise generated by moving a flight path, the reduction in noise achieved by insulating a house, etc. The tools can also be used to help an audience understand the technical noise descriptors used in noise assessment reports.

Figure 14.1 Two screenshots from an audio/visual presentation.

Strengths

  • Gives a person a ‘real life’ experience of what the noise is like and clearly demonstrates the variations between different types of noise events.
  • Allows a group debate, with an expert facilitator, in a manner that goes beyond a public meeting that relies purely on static information.
  • Holding the presentations is a clear indication that an airport is taking a consultation process seriously and is attempting to directly answer questions raised by the public.

Weaknesses

  • The presentations are a ‘one hit’ experience—a member of the audience is not able to revisit the information in order to think about it and may not be able to effectively remember noise information presented in this way for long.
  • The presentation is generally given in a group meeting and the noise effect may not be perceived to be the same as in the person's home.

Suggested uses

  • consultation processes for major airport projects such as the building of a new runway
  • informing groups, for example airport consultative committees, about aircraft noise issues
  • training airport staff involved with answering aircraft noise complaints

Data source/software

  • Proprietary products

Figure 14.1 Two screenshots from an audio/visual Presentation

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15. Internet flight path sites

Overview

A number of overseas airports now provide the facility for flight paths to be viewed on their websites.

These sites allow a user to inter-actively find information about the flight paths in the vicinity of an airport (or airports in an area where there is more than one airport). Some of these sites allow the viewing of flight paths with a 10-minute delay. Another webpage design allows the flight paths to be viewed with a one day delay. The sites show a picture which is updated as the aircraft move. The base display uses colour codes to differentiate between arriving and departing, and jet and non-jet, aircraft. It also shows aircraft that are in transit and bypassing local airports. A user is able to zoom in or out on the image and can also ascertain the altitude of individual aircraft. In addition an individual aircraft can be selected and tracked as it traverses through the airspace. The sites also allow the user to re-play the flight tracks for any selected time period contained in the flight track database.

Figure 15.1 Two screenshots from the Oakland International Airport web-based flight track and noise viewing system.

Strengths

  • Demonstrates transparency—the airport is being open about what is happening.
  • Allows the public to see for themselves where the flight paths are, rather than having to receive a flight path map from a noise complaints centre.
  • Immediacy—members of the public can receive almost real time information.

Weaknesses

  • The websites show what is happening at any particular time but do not explain why it is happening, for example, why a particular runway is being used.
  • The information is only available to people who have access to the Internet.
  • The ‘snap-shot’ approach of these sites does not show an aggregated picture of flight path patterns.

Suggested uses

  • responding to noise complaints
  • providing advice to prospective house buyers
  • informing the public about how airports operate
  • allowing compliance with noise abatement procedures to be informally checked

Data source/software

  • Proprietary products

Figure 15.1 Two screenshots from the Oakland International Airport web-based flight track and noise viewing system

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Index 1 2 3 Glossary

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Last Updated: 9 July, 2014