Quiet please! Fighting noise pollution
Box 4 | Traffic noise – sources and solutions
Traffic noise is probably the most serious and pervasive type of noise pollution. Studies have shown that on a daily basis almost 40 per cent of Australia’s population is exposed to undesirable levels of traffic noise and a further 10 per cent is exposed to excessive levels.
Australia has close to 13 million registered motor vehicles, about two vehicles on the road for every three people. Passenger vehicles make up the great majority (80 per cent), followed by light commercial vehicles, trucks, motorcycles and buses.
Traffic noise has become a serious problem now because of inadequate urban planning in the past. Homes, schools, hospitals, churches, libraries and other community buildings were routinely built on main roads without buffer zones or adequate soundproofing. The problem has been compounded by increases in traffic volumes far beyond the expectations of our early urban planners.
Sources of traffic noise
At low speeds, most traffic noise is caused by vehicle engines, transmissions, exhausts and brakes. The stop-start braking and acceleration during peak-hour congestion also increases noise levels. On freeways where speeds are high and relatively constant, most noise is caused by a combination of tyre contact with the road and aerodynamic drag over the vehicle.
Trucks and motorcycles combine to make up 7 per cent of vehicles on our roads, but they are largely responsible for the peak noises that stand out from the steady background rumble. It is these sharp and intermittent noises that are more likely to cause sleep disturbances and to contribute to other physical and psychological problems.
Solving the problem of traffic noise
A 2001 report by the National Road Transport Commission (NRTC) found that, in comparison with Europe, Japan and the United States, Australian regulations permit up to double the noise emission levels from some vehicles. The report recommends adopting new noise levels in line with international standards, and tougher regulations to control the performance of exhaust systems. Another recommendation is to provide more resources to local authorities to ensure that owners, particularly those of older cars, comply with the new regulations.
One target of the NRTC report is the excessive noise from trucks that use engine braking as a backup to conventional wheel braking. While engine braking is an indispensable safety device, fitting trucks with improved and relatively inexpensive mufflers can significantly reduce the noise levels.
The installation of noise barriers along major roads and freeways is another way to combat traffic noise. The barriers deflect noise from adjoining urban areas and can be made from relatively light and inexpensive materials such as timber, fibro-cement sheet or Perspex. An effective barrier needs to be long enough and high enough to deflect noise from the area that is to be protected. Usually this means that the barrier blocks the line of sight to the noise source. Any gaps in the barrier (eg, driveways) decrease its effectiveness.
A combination of strategies that include noise barriers, lower vehicle noise levels and better urban planning will help reduce the impact of traffic noise in the future.
Boxes
Box 1. Health issues related to noise pollution
Box 2. What is noise?
Box 3. Planning to reduce airport noise
Box 5. Soundproofing noisy buildings
Related sites
Australia's vehicle noise limits too loud: NRTC report (National Road Transport Commission, Australia) Highway traffic noise (US Department of Transportation)
Keeping the noise down – highway traffic noise barriers (US Department of Transportation)
Page updated August 2004.