What are the effects of
aircraft overflight noise?
How is aircraft overflight noise
measured?
Effect on sleep
N70 noise metric
What are the impacts on land
use planning?
What are the impacts on
property values?
Noise Management Measures
Aircraft
overflight noise can affect people in many different ways. It can, for example, make
conversation difficult, disturb those watching television or listening to the radio, or
interfere with other forms of communication. Aircraft noise can also result in various
forms of sleep disturbance. People can also be annoyed or be frightened by aircraft
overflight noise. Other effects include reduction in housing values, impacts on wildlife
and reduced enjoyment of recreational and natural areas. However the noise from aircraft
must be considered in an holistic sense by looking at the full perspective which includes
other external noises like from highways and rail.
The way the ear responds to different types
of noise is usually measured by using the A-weighted decibel (dBA). Because of the way the
dBA scale is calculated, a 10 dBA increase in noise is generally equivalent to doubling
the loudness of the noise.
A useful way of describing aircraft noise
is to use the maximum noise level of the particular aircraft as it flies overhead. This
has been measured in dBA and allows an estimate to be made of the level of disturbance to
sleep and communication.
Another, and more common, measure of
aircraft noise exposure in Australia is the Australian Noise Exposure Forecast (ANEF)
System. This system takes into account the noise level of each aircraft passing overhead,
the number of movements and the time of day or night. An Australian Standard (AS 2021) has
been developed based on this system and provides local authorities with guidelines for
planning land uses around airports. This Standard has been updated several times,and the
latest version is -2000.
The ANEF system yields a number of measures
which are used for different purposes. One of these, the Australian Noise Exposure Concept
(ANEC), which is based on indicative data on aircraft types, aircraft operations and
flight zones, is used to provide a measure of aircraft noise impacts in an EIS. The
results are exactly the same as the ANEF, but the ANEC is indicative and not certified by
DoTRS.
The community-wide response to aircraft
noise can sometimes be partially assessed in economic terms through an estimate of the
potential reduction in property values. There are, however, other impacts that cannot be
so precisely defined, such as effects on health and other social impacts on individuals
and communities.
One
of the issues is whether night-time operations at an airport should be restricted by a
curfew (as are operations at Sydney Airport). Using data from the Second Sydney Airport
studies, this section shows how the disturbance to sleep can be studied. Table 1 summarises
the potential for each airport option to disturb sleep when the airport is operating at 30
million passengers per year. The table provides an estimate of the frequency of awakenings
that may occur due to average operations of the airport options. Also provided is the
‘worst case’ prediction of the number of people affected by noise events
exceeding 60 dBA during the night (10.00 pm to 6.00 am). An external noise level of 60 dBA
approximates an internal level of 50 dBA with windows open, which is within the range in
which sleep can be disturbed.
| Table 1: Disturbance to Sleep for the Airport
Operating at 30 Million Passengers per Year |
| Noise Indicator |
Population
Affected1 |
|
OPTION
A |
OPTION
B |
OPTION
C |
| People that may, on
average, be awoken the following times: |
|
|
|
| once a night |
less
than 100 |
less
than 100 |
less
than 100 to 100 |
| once every 2
nights |
500 to
1,000 |
300 to
800 |
400 to
600 |
| once every 5
nights |
6,000 to
8,000 |
3,500 to
6,000 |
1,500 to
17,000 |
| People that may
experience the following number of noise events greater than 60 dBA on a worst case night: |
|
|
|
| greater than 5
events |
18,000
(4,500)2 |
19,000
(4,500)2 |
47,000
(2,000)2 |
| greater than 2
events |
124,000
(60,000)2 |
108,000
(39,000)2 |
178,000
(48,000)2 |
| Notes: |
1: Based on population projections
for 2016.
2: Figures in brackets represent impacts with the adoption of
potential noise management measures.
3: There are limitations in the accuracy of predicting future
populations. Estimates of population greater than 10,000 have been rounded to the
nearest 1,000; estimates of population between 1,000 and 10,000 have been rounded to the
nearest 500; and estimates of population less than 1,000 have been rounded to the nearest
100. Estimates of population less than 100 are expressed as less than 100.
4: Impacts assume all residential properties within the 35 ANEC
contour would be acquired. |
Aircraft noise can interfere with
communication such as conversation, watching television and listening to the radio.
The number of noise events exceeding 70 dBA over a 24-hour period tends to indicate the
degree of disruption to normal domestic communications. When outside noise levels are
below 70 dBA, communication inside the home is unlikely to be disrupted, while above 70
dBA some interruption is likely. The same comment applies in regard to schools, except
that the critical outside noise level is 65 dBA.
Disturbance to domestic communication was therefore measured in terms of N70
data; that is, the number of times in an average day that a location is exposed to
external aircraft noise of more than 70 dBA. N65 data were used to assess
disturbance to educational facilities.
Table 2 summarises the impacts of aircraft overflight noise from the Sydney
Airport options on communications within domestic situations when the airport is operating
at 30 million passengers per year. The N70 chart is shown graphically here, with the maximum extent of the N70 contours for an
airport option operating at 30 million passengers per year. These contours show the
outside extent of a large range of N70 levels which resulted from examining the
combinations of assumptions about air traffic movements and the different ways the airport
might be operated. I've got an ANEF drawing of the same airport and
flights (actually its an ANEC, but there's no difference). See how the N70 ties to the
ANEF 15.
Table 3 summarises the potential impacts on existing educational facilities for
each Sydney airport option.
| Table 2: Disturbance to Communication for the
Airport Operating at 30 Million Passengers per Year |
| Noise Indicator |
Population
Affected1 |
|
OPTION
A |
OPTION
B |
OPTION
C |
| People that may
experience, on average, the following number of noise events over 70 dBA a day: |
|
|
|
| greater than 100
events |
400 to
900 (NR)2 |
300 to
700 (NR)2 |
300 to
500 (NR)2 |
| greater than 50
events |
2,500 to
5,000 (1,500)2 |
2,000 to
4,000 (NR)2 |
700 to
1,000 (NR)2 |
| greater than 20
events |
8,500 to
9,500 (5,000)2 |
7,000 to
9,500 (NR)2 |
6,000 to
17,000 (NR)2 |
| greater than 10
events |
15,000
(10,000)2 |
16,000
to 17,000 (NR)2 |
60,000
to 72,000 (32,000)2 |
| Notes: |
1: Based on population projections
for 2016.
2: Figures in brackets represent impacts with the adoption of
potential noise management measures. NR means no reduction in impact.
3: There are limitations in the accuracy of predicting future
populations. Estimates of population greater than 10,000 have been rounded to the
nearest 1,000; estimates of population between 1,000 and 10,000 have been rounded to the
nearest 500; and estimates of population less than 1,000 have been rounded to the nearest
100. Estimates of population less than 100 are expressed as less than 100.
4: Impacts assume all residential properties within the 35 ANEC
contour would be acquired. |
| Table 3: Aircraft Overflight Noise Impacts on
Existing Educations Facilities for the Airport Operating at 30 Million Passengers per Year |
| Noise Indicator |
Education
Facilities1 |
|
OPTION
A |
OPTION
B |
OPTION
C |
| Educational facilities
that may experience, on average, the following number of noise events over 65 dBA between
9.00 am and 3.00 pm: |
|
|
|
| greater than 20
events |
15 (5)2 |
13 (2)2 |
25 (3)2 |
| greater than 10
events |
20 (14)2 |
20 (11)2 |
75 (26)2 |
| Notes: |
1: Definition of educational
facilities includes child-care centres.
2: Figures in brackets represent impacts with the adoption of
potential noise management measures. |
The maximum extent of the ANEC contours for each of the airport options operating
at 30 million passengers per year is shown in the ANEC chart graphically here. These contours show the outside extent of a large
range of ANEC levels resulting from the examination of the combinations of assumptions
about air traffic movements and the different ways the airport might operate. They can be
compared to the N70 contours to get a feel for the inter-relationship.
Table 4 provides
a summary of predicted populations impacted by ANEC levels when the airport is operating
at 30 million passengers per year. It also shows the populations that might be affected if
noise management measurements are adopted. In estimating likely noise reaction from these
values, allowance must be made for the additional reaction to the introduction of a new
noise source.
| Table 4: Populations Impacted by ANEC Levels for the Airport Operating at 30
Million Passengers per Year |
| Noise Indicator |
Population
Affected1 |
|
OPTION
A |
OPTION
B |
OPTION
C |
| People that may experience
the following ANEC levels: |
|
|
|
| greater than 30 |
200 (NR)2 |
less than 100
to 200 (NR)2 |
less than 100
to 300 (NR)2 |
| greater than 25 |
700 to 1,000
(NR)2 |
500 to 800
(400)2 |
300 to 700
(NR)2 |
| greater than 20 |
4,500 to
6,000 (2,500)2 |
3,500 to
5,000 (2,000)2 |
900 to 1,500
(NR)2 |
| greater than 15 |
11,000 to
14,000 (8,000)2 |
11,000 to
14,000 (7,500)2 |
15,000 to
19,000 (10,000)2 |
| Notes: |
1: Based on population projections
for 2016.
2: Figures in brackets represent impacts with the adoption of
potential noise management measures. NR means no reduction in impact.
3: There are limitations in the accuracy of predicting future
populations. Estimates of population greater than 10,000 have been rounded to the
nearest 1,000; estimates of population between 1,000 and 10,000 have been rounded to the
nearest 500; and estimates of population less than 1,000 have been rounded to the nearest
100. Estimates of population less than 100 are expressed as less than 100.
4: Impacts assume all residential properties within the 35 ANEC
contour would be acquired. |
The effect of aircraft noise on
residential property values provided a basis for comparing the airport options. It does
not provide a precise measure of possible devaluation of individual properties.
The analysis addressed only the direct
impacts on dwellings in areas potentially affected by noise of greater than 15 ANEC. There
is also likely to be more indirect impacts on property values such as the impacts of
construction of off-airport site infrastructure and changes to land use planning controls.
The impacts of aircraft noise from an
airport could be reduced by the adoption of noise management measures. The most effective
measures would be to refine flight paths and restrict some types and times of runway and
flight path use to minimise overflying of residential areas, particularly at night. A
noise management plan could be developed as part of the environmental management framework
for the airport.
The relative performance of airport options
in terms of aircraft overflight noise would vary depending on which noise indicator is
examined. The implementation of noise management measures could also have varying results
depending on the airport option. Consequently it is difficult to provide a definitive
ranking between airport options.
