Quiet please! Fighting noise pollution
Box 5 | Soundproofing noisy buildings
Most of us spend the majority of our time indoors, but we are only partially protected from the noise pollution of modern cities. Noise from road traffic or low-flying aircraft enters through the external walls of a building or noise generated in one room annoys occupants elsewhere in the building.
Structure-borne and airborne noise
Noise can pass from one room to another either through the building structure itself (structure-borne noise) or through the surrounding air (airborne noise). Airborne noise is the more common and occurs, for example, when loud music in a living area interferes with people sleeping in bedrooms. Airborne noise can pass from one room to another along a variety of paths such as open doors and windows, openings in walls separating the rooms, stairwells, or heating and air-conditioning ducts.
Structure-borne noise occurs when the building structure itself is made to vibrate; for example, a washing machine in contact with a wooden floor, a saucepan falling to the kitchen floor, and the impact of footsteps on hard floors.
Soundproofing guidelines
The guidelines for soundproofing in the Building Code of Australia (BCA) date back to a time when most Australians were leading a much quieter life in the suburbs.
At least four significant failings have been identified with the present BCA:
- The code only applies to internal walls, not the external walls of a house. This means there are no controls over loud street noises entering a house or loud party noises leaking to the outside.
- The number of complaints from owners indicate that the recommended amount of sound insulation required for internal walls is too lenient.
- The code only applies to so-called airborne sounds, not structure-borne or impact sounds.
- The code assumes that the noisiest areas in a house are the kitchen, laundry and bathroom. Today it is the living room, with powerful entertainment systems and hard floor surfaces, that is probably the noisiest in the house.
Changes to the Building Code of Australia
Currently the Australian Building Codes Board is considering strengthening the sound insulation provisions of the BCA. Any changes would almost certainly strengthen the sound insulation requirements for internal walls of buildings. How well a wall insulates sound is measured by the weighted sound reduction index. The minimum allowable value of the index for internal walls in the current building code is 45 decibels (dB). Increasing the index to 55 dB would approximately halve the amount of unwanted sound leaking through a wall. It would also bring Australia into line with building codes in countries such as Germany, Denmark, Great Britain and New Zealand.
The new code would also need to recommend a minimum requirement for 'impact sound insulation' of floors. Currently there is no requirement, because the code assumes that carpet will be used as a general floor covering, ignoring the fact that homeowners are turning to hard floor coverings such as polished boards and ceramic tiles.
Good sound insulation is expensive. The proposed changes are expected to add an extra 2 per cent to the construction costs of a building. Also, the extra thickness of walls, floors and ceilings would mean that 3 per cent fewer dwellings could be fitted onto a development site. Developers would therefore need to charge more for each dwelling to maintain their profit margins. Nationally, the changes could cost the building industry an estimated $115 million a year.
Boxes
Box 1. Health issues related to noise pollution
Box 2. What is noise?
Box 3. Planning to reduce airport noise
Box 4. Traffic noise – sources and solutions
Related site
Noise control (Your Home, Australian Government)
Page updated February 2006.