Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Professor Peter W. Newton, CSIRO Building, Construction and Engineering, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06747 7
Liveability: environmental quality (continued)
Quality of life is affected by occupational noise at work, and by environmental noise outside and at times infiltrating the home. While nobody dies as a result of noise and very few people are seriously injured by it, the cumulative impacts of noise pollution are being increasingly acknowledged.
Noise due to transport, industry and the community is perceived to be increasing in cities. Transport noise, predominantly due to road and air traffic, is of particular concern.
Aircraft noise - as airports grow and develop in line with the overall growth of aviation, noise generation increases as a result of the additional flight activity. Total annual scheduled aircraft movements from Australian airports grew by 40% to 1 266 335 between 1986-1987 and 1996-1997. Figure 70 shows annual aircraft movements by scheduled services in 1997-1998 (note the figure excludes private flights).
Figure 70: Annual aircraft movements from Australian airports, 1997-98. [HS Indicator 9.7]
Source: DTRS (1999).
Aircraft overflight noise can, for example, make conversation difficult, disturb those watching television or listening to the radio, result in sleep disturbance, and reduced enjoyment of recreational areas (Sydney West Airport Taskforce 1999). Australian Noise Exposure Forecast (ANEF) contours indicate exposure to aircraft noise across cities based on the noise level of each aircraft passing overhead, the number of movements and the time of day or night. The degree of disturbance depends upon both the noise from aircraft and the number of overflights. The need to combine these factors has led to the development of noise unit measures. The ANEF system combines noise and frequency of flights and adds a weighting according to time of day. Every flight between 7 pm and 7 am is counted as equivalent to four daytime flights.
Mapped ANEF contours are used for planning for suitable land uses around all Australian airports. For example, new private dwellings should not be built within 25 ANEF contours. They have also been used to determine the need for impact amelioration by acquiring or insulating dwellings.
Growth in air traffic and noise, Sydney airport.
In contrast to the ANEF, which shows areas affected by aircraft noise, the Person-Events Index (PEI) allows comparison of how people are affected by noise between airports and cities. The total noise load generated by an airport is computed by summing, over the exposed population, the total number of instances where an individual is exposed to an aircraft noise event above a specified noise level over a given time period. For example, if 20 000 persons were exposed to a single noise event greater than 70 dB(A), the PEI (70) would be 20 000. A second event would double that to 40 000. PEIs for some Australian cities are given in Table 55.
|Airport||No. of persons exposed
to >10 events/day >70 dB(A)
|PEI (70) A (millions)|
|Major international airport B||190 000||27.0|
A PEI (70) is the total number of instances on the average day where a person is exposed to a noise event greater than 70 dB(A), and is a measure of the total noise load generated by the airport.
B The `major international airport' is an anonymous USA airport used for comparison.
Source: Southgate et al. (2000).
Sydney, with the largest number of aircraft movements and its airport close to the city, suffers particularly from aircraft noise. Population exposure to noise from just one B747-2000 taking off from Sydney Airport is equivalent to the entire day's aircraft noise exposure in Brisbane (Southgate et al. 2000).
Traffic noise - cars and trucks are the major cause of noise in urban areas. It has been estimated that more than 70% of environmental noise is due to road traffic. Increasing levels of traffic and increasing goods movements leads to increasing exceedances of transport noise level guidelines. These are set, in most Australian states at between 63 and 68 dB(A) L10 (18 hour), the sound level which should not be exceeded more than 10% of the time during the 18-hour period. In New South Wales, Leq measures an equivalent steady-state sound level containing the same acoustic energy as the time-varying level over the period, and is set at 65 dB(A) over 24 hours or 55 dB(A) at night. Brown (1994) estimated that nearly one in 10 dwelling units or 19% of the population in Australian urban areas with populations of greater than 100 000 is exposed to L10(18 hour) noise levels of 68 dB(A) or greater. Traffic noise 'black spots', usually located close to major road routes, are the main sources of the problem.
Despite less stringent guidelines, OECD targets are Leq 55 dB(A) for 6 am to 10 pm and Leq45 dB(A) for 10 pm to 6 am. Australia compared well with other OECD countries in terms of cumulative population exposure to traffic noise above 65 dB(A)Figure 71).
Figure 71: Percentage of population exposed to excessive traffic noise in some OECD countries. [HS Indicator 9.1]
Source: OECD (1991).
Noise penetration - while fences, walls or hedges may play some part in limiting noise penetration into dwellings, the acoustic performance of the dwelling itself is more important. For a typical detached dwelling with open windows, the overall noise reduction from the building itself may be as low as 10 dB(A). Dwellings subject to aircraft noise or traffic noise levels from a busy street of up to 80 dB(A) need to give better protection from noise intrusion. Choice of building materials or addition of insulating materials for greater sound transmission loss can have a significant impact. For example, timber, prevalent in the construction of Queensland houses, allows more transmission than brick. An Australian sound transmission class (STC) rating system allows architects and builders to compare building component performance. However, it is the entire structure which determines overall noise effectiveness. Windows and doors are generally the weakest links. A double-glazed and sealed window can reduce noise by up to 40 dB(A) compared to a single-glazed window with no seals at 20 dB(A) closed or 10 dB(A) open (SPCC 1991). However, designers need to ensure sufficient ventilation so that noise pollution is not replaced with indoor air pollution.
Containing sounds within buildings can be equally important to reduction of external noise. Noise from air-conditioners, swimming pool filters, domestic appliances and plumbing can be a problem. Noise from a toilet system flushing and refilling can exceed 70 dB(A) (Narang 1992). Residents also may be disturbed by loud conversation, parties or music. The impact of the latter is increasing. As technology for amplifying music becomes less expensive, a small device bought relatively cheaply can now output music louder than a brass band. The Building Code of Australia has requirements for minimum sound insulation, in the form of mandatory minimum STC, for components to protect adjacent occupants in multi-unit dwellings, but there are no standards for detached dwellings sited close to neighbours, or indeed internal partitions within dwellings. As tolerance to noise varies considerably, it is desirable to aim for higher acoustic performance. Good design can do much to improve the acoustic performance of dwellings. This can range from choice of construction materials, through the siting of plumbing, to small details such as automatic door closers to limit slamming.
Noise barriers on major arterials and freeways.
Impact on residents - environmental noise is unpleasant when experienced outdoors, but most severely impacts health and well-being when it penetrates into and throughout buildings. This is due both to the higher percentage of time spent indoors - over 90% of time for the populations in larger cities - and to less tolerance to indoor noise. Typical indoor activities such as working, studying, reading, listening to music, watching television and, in particular, sleeping or trying to sleep require a quiet environment. Noise is often defined as unwanted sound; thus noise is context-dependent.
Many complaints about excessive environmental noise relate to concerns about disturbed sleep. Satisfactory background noise levels, as given in the Australian Standard AS 2107-1987 in private dwellings, are set at 35 dB(A) for work areas. The standard is set lower for bedrooms, varying from 30 dB(A) for inner suburban dwellings to 25 dB(A) in the outer suburbs or rural areas. Findings from studies of sleep disturbance, measured by awakening, changes in sleep state or after-effects, reflect the considerable variation in people's response to noise. Suggested peak permitted noise levels vary from 45 to 68 dB(A), depending on ambient noise (Griefahn 1991), and disturbance is related to both the number and maximum level of noise events (Bullen et al. 1996).
While physiological symptoms such as headaches are reported, the most palpable human impact is general annoyance. Contrary to popular belief, studies also show that people do not become accustomed to excessive noise. They do become less likely to be startled by expected noise events. This is perhaps why people are more tolerant by a factor of 5 dB(A) to noise from trains, which run regular services, than to noise from trucks (Narang 1992).
In all Australian cities, the overall amount of environmental noise is increasing and larger proportions of the population are suffering from exposure to noise. This is due to both growth in city activities and changes in urban form. As housing density increases, people increasingly hear noise from their neighbours, and this can be exacerbated in multi-unit dwellings with shared walls. There is thus a growing impact on community health and well-being.
Noise amelioration measures are of three types: limiting or eliminating noise at the source; providing barriers between the source and residences; and insulating the residences against noise. None are sufficient in themselves. Packages of measures will be needed to adapt to different situations, especially since a number of measures being introduced to reduce other environmental hazards have perverse effects with respect to noise pollution. For example, traffic calming devices and changes in urban form to reduce traffic may increase environmental noise.
Noise problems also extend over more of the day as big cities become 24-hour cities. Levels of noise that are tolerable by day may not be tolerable at night, engendering increased stress among the population. It cannot be assumed that people will develop immunity to noise. It has been shown that, while they may become resigned to the impost, they will still suffer impairment. Constant exposure to unacceptable noise can have cumulative effects on health. These can range from the impacts of disturbed sleep to industrial deafness caused by cumulative noise load on workers. While improved health and safety regulation, together with a decline in numbers of workers engaged in heavy manufacturing industries, have combined to reduce the incidence of industrial deafness, education is needed to ensure that exposure to very loud music for recreation, when added to workplace noise is not a new cause of deafness. Improved housing and urban design and utilisation of insulative materials is also overdue.