Passive Design

Designing the building and the spaces within it to benefit from natural light, ventilation and even temperatures.

Controlling noise

Noise is a nuisance and can contribute to loss of sleep, stress, and ill health.

For a house to be comfortable, it must be designed so that its layout and structure keep noise to acceptable levels and that most activities can be carried out without undue interference from internal or external noise.

To design for noise control, it is important to understand potential sources of noise, types of noise, and how noise travels along sound paths.

The best results will come when acoustic performance is considered early in the design process and then followed right through during construction. Installers and contractors need to understand the concepts and avoid errors such as installing a duct through a completed acoustic separation.

Sources of noise

The most common sources of noise in a house are:

  • externally generated noise from outside the site such as traffic, trains, aeroplanes, neighbours and schools
  • externally generated noise from within the site such as wind on the building, rain on the roof, heat pumps and water pumps
  • internally generated noise such as loud conversation, washing machines, dishwashers, stereos, televisions and air conditioners
  • impact noise through the structure such as footsteps (particularly on stairs) and children playing
  • noise from services such as toilet flushing.

Noise can be airborne (for example, noise from traffic or a television set) or structure-borne (for example, the sound of a door slamming or footsteps from someone upstairs – this is known as impact noise).

Controlling noise

Where possible, noise should be controlled at source – for example, by specifying quiet appliances.

Where noise cannot be controlled, its effects can be reduced through a combination of good building design and layout (which ensures, for example, that quiet areas of the building are located away from sources of noise, or there are buffers between the noise and occupied spaces), and structural features such as sound attenuating walls and windows that limit airborne and impact noise. See controlling noise through design and layout for detail.

Building Code minimum requirements

Building Code clause G6 Airborne and impact sound applies to neighbouring tenancies, and imposes limits on sound transmission in walls, floors and ceilings, and impact sound in floors. This only applies to connected dwellings. G6 does not require acoustic privacy for external walls and windows – where adjacent dwellings are not connected, there are no requirements for sound insulation, regardless of how close they are.

The minimum sound insulation requirements for dwelling units set by the performance requirements of G6 are:

  • an STC (sound transmission class) of at least 55 for inter-tenancy walls, floors and ceilings
  • an IIC (impact insulation class) of at least 55 for inter-tenancy floors.

The STC rating is the noise reduction in decibels (dB) that a wall or floor provides. If a wall has an STC rating of 55, then a 75dB sound on one side is generally reduced to 20dB on the other side (there are different impacts on different frequencies). The IIC rating gives decibels resisted in transmission of impact noise.

Of course, designers can take a Code-plus approach and design something better than the poorest level legally permissible. STC 60+ provides good acoustic privacy and can be achieved with readily available materials and details.

To meet these requirements, a specific acoustic wall and floor construction system must be used. Information on sound ratings of specific systems is available in manufacturers’ trade literature.


Updated: 24 April 2020