Noise control

Good building design can help achieve a safer and secure living environment. These design features can be incorporated upfront in the design and construction phase or through ongoing modification and maintenance.

Noise types and levels

There are 2 types of noise to consider for your home:

• Airborne noise is sound that travels through the air from common sound sources such as voices, TVs and radios. Weighted sound reduction index (Rw) is the metric used by the National Construction Code (NCC) to rate the effectiveness of a structure as an airborne noise insulator. Rw rating has replaced the previously used sound transmission class (STC), but the 2 rating systems are similar. An increase of one Rw unit approximately equals a reduction of 1 decibel (dB) in noise level. An increase of 10 Rw units approximately halves the sound transmitted.
• Impact noise (also called structure-borne noise) is produced when part of the building fabric is directly or indirectly affected. Energy passes through the structure and creates noise in nearby rooms. Examples are heavy footsteps (particularly on bare timber or tile floors), banging doors, scraping furniture, vibrations from loud music, and plumbing noises. The impact insulation class (IIC) is used to rate the impact noise insulation of floors.

Some typical values are given in the following table. Note that it is not a linear scale — going from 50dB to 100dB is not twice as loud but 16 times as loud and from 60dB to 30dB is not half as loud but one-eighth as loud.

Sound levels and their perception

Site

Consider noise sources such as shops, hotels, and garbage and recycling collection when siting, buying or renovating your home and locating windows.

There are proprietary fencing or ‘sound wall’ options designed to provide noise abatement (reportedly up to 43dB). These solutions can result in large, potentially unattractive areas of vertical hard surfaces but they can be improved with the addition of decorative elements that also contribute to sound attenuation. Large masonry-based sound walls and fences are generally appropriate on the boundary of domestic dwellings with more public areas rather than between dwellings and suburban backyards. Place driveways and garages away from bedrooms and living rooms.

Dense vegetation can significantly reduce noise transmission in a number of ways — a soft earth surface reduces the intensity of low frequency sound by absorbing its energy, and leaves and stems scatter high-frequency sound waves. Place walls, fences, trees and screening vegetation between the noise source and your home.

 

Floor plan and design

The best protection against noise is to avoid making it in the first place, or ensure that noise sources are not too close. Noise levels vary through different times of the day, so it is worthwhile to try and take account of when noise is, or might be, generated.

Also take account of both direct and reflected sound. A passive home is designed to encourage airflows that distribute heat or ‘coolth’ through the building. This tends to enhance sound transmission between the building’s internal spaces, so careful consideration of the sound transmission and reflection qualities of internal surfaces is especially important.

Source: CSR Gyprock

Sound ‘leaks’ through gaps surprisingly easily, so your building’s construction material, design and layout can make a big difference:

• Locate quiet rooms as far away from noise sources as possible, without compromising passive solar design principles.
• Install windows away from noise sources if possible and select sound absorbing types of glazing.
• Locate noisy areas together and away from quiet areas.
• Avoid putting laundries, bathrooms or living rooms next to, above or below bedrooms without adequate sound insulation. Consider mounting noisy appliances on sound-absorbing pads.
• Accommodate teenagers by providing extra soundproofing for their rooms and locate them away from adult living and sleeping areas, and neighbours.

 

Outdoor noise sources

Situate noisy areas such as swimming pools and outdoor living areas away from neighbours’ windows. Erect appropriate sound barriers and plant vegetation to reduce or modify the impact of noise both from and to your home.

Avoid using hard exterior surfaces such as concrete paving, which reflects sound rather than absorbs it. Softer surfaces are more desirable, particularly in higher density housing, as they absorb sound. Permeable surfaces also reduce stormwater runoff.

Make sure outdoor noise sources (air-conditioning units, pool pumps) will not be a nuisance for neighbours. There are laws governing noisy air-conditioners and pumps that may annoy neighbours and most air-conditioners in Australia have a label that specifies the amount of noise they make. The smaller the dBA number on the label, the quieter the air-conditioner. Get specialist advice from the supplier or installer. Buy the quietest air-conditioner suited to your needs, and install it as far as possible from your neighbour or in a well-shielded location. If pumps cannot be placed far enough away, build a noise reduction enclosure, but make sure it does not undermine the efficiency of the equipment by blocking air flow.

Evaporative coolers on roofs can be a major noise problem: choose a quiet model and locate it on a roof slope away from neighbours.

 

 

Construction

Materials

Construction materials with high thermal mass are much better at reducing the transmission of airborne noise than low mass materials.

High mass construction can provide good acoustic insulation between rooms and apartments, or from outdoor noise, although it may also reflect sound and transmit impact noise.

To effectively reduce impact sounds, materials need to be both high mass and high loss (sound absorbing). Damping using high-loss material (for example, rubber- or plastic-based materials) reduces the transmission of impact sounds. High-density foams and various rigid and flexible sheet products designed for this purpose are commercially available.

There are also ways to improve the acoustic performance of low mass construction.

Sound-absorbing surfaces added to the surface of walls and floors can reduce reflected sound but not direct noise transmission. Carpet consistently outperforms other floor coverings in this regard. It reduces reflection and absorbs impact but has significant waste implications. Hard and even many resilient floor coverings (that is, soft underfoot, sound absorbing) require an additional sound-absorbing substrate layer to prevent the transmission of impact sound, such as hard shoe heels.

The Rw ratings of some typical wall and floor construction methods are outlined in this chapter. Heavy dense materials, such as concrete, are generally better for sound insulation but a range of lightweight solutions are also available.

 

Walls

The mass of plasterboard per unit area is very important in determining the noise insulation value (Rw): the heavier the plasterboard, the better. Most manufacturers produce a high-density acoustic board in varying thicknesses. Due to handling limitations, multiple layers are often the preferred solution. Joints should be staggered in multiple layer applications.

Construction options include:

• Rw32 — Using 10mm plasterboard on 100 × 50mm timber studs at 450mm centres provides very little sound insulation and is not recommended for occupied rooms.
  

  

   

• Rw42 — 100mm low density AAC block with 10mm adhered plasterboard both sides.
  

  

   

• Rw45 — 90mm calcium silicate brick with adhered 10mm plasterboard both sides. This complies with the Building Code of Australia minimum for adjoining dwellings.
  

  

   

• Rw50 concrete — 90mm solid concrete block with adhered 10mm plasterboard both sides.
  

  

   

• Rw50 timber frame — 16mm fire protective plasterboard on staggered timber 70 × 45mm studs at 600mm centres both sides with 120 × 35mm timber plates and 50mm glass fibre batts.
  

  

   

High density insulation, multiple layers of plasterboard and foam backed plasterboard also help control noise transmission — internal stud walls can be filled with high density insulation which provides acoustic insulation and also increases thermal resistance. This is particularly useful between inhabited and uninhabited spaces like laundries.

Pay special attention to details that might affect the integrity of sound insulation such as power points and plasterboard joints. Offset power outlets and locate them in different sections of the wall cavity. Use sealed power outlets to prevent air leakage.

 

Ensure the joints overlap and offset joints on opposite sides of the wall when using double layers of plasterboard.

 

The National Construction Code (NCC) specifies the minimum required Rw (airborne) + Ctr (impact) sound values for separating wall construction in new single dwellings (Class 1 buildings). For further information, please refer to Part 3.8.6 of Volume 2 of the NCC. Exceeding the minimum specifications is highly recommended, particularly given the trend towards higher-density living. The NCC does not specify IIC, but certain construction types are ‘deemed to comply’.

National Construction Code Rw requirements for walls between adjoining dwellings

Structure	Minimum reduction index (Rw)
Floors above dwellings	50
Walls between a bathroom, laundry or kitchen and a habitable room in adjoining dwelling*	50
Other walls	45

*These walls must also have a satisfactory level of impact insulation as outlined in the code

Source: ABCB 2011

Rw levels in the NCC only consider individual building elements as measured in a laboratory. Sound transmission properties of the structure as a whole or on-site construction practices are not taken into account. These can reduce the effective value by up to 5Rw because of flanking sound transmission paths, for example through structural components.

For the NCC minimum requirements for Rw (airborne) + Ctr (impact) sound values for separating wall construction in new single dwellings (Class 1 building) please refer to Part 3.8.6 of Volume 2 of the NCC.

Floors

Avoid hard floor surfaces above ceilings without good sound insulation. Use cork, carpet or impact-absorbing finishes instead of bare timber or tiles. Install bulk insulation under floors to damp down noise and reduce noise transfer.

Use proprietary noise reduction underlay to increase both Rw and IIC ratings of floors. They are ideal for reducing sound transmission on existing floors within a home. Use low-density coverings such as carpet, which will have little effect on Rw but will greatly reduce both impact noise (increasing the IIC by about 20 points) and internal sound reflection.

Constructions options include:

• Rw35 — Bare 20mm floorboards on 200 x 50mm joists at 450mm centres, with one layer of 13mm plasterboard, provides very little sound or impact insulation and is not recommended.
  

  

   

• Rw48 — 150mm concrete slab (365kg/m²) with 10mm of plaster.
  

  

   

• Rw50, IIC 50 — Bare 20mm floorboards on 200 × 50mm joists at 450mm centres, with 2 layers of 16mm fire protective plasterboard on furring channels and resilient mounts, and 100mm batts. Using carpet and underlay will increase the IIC to 70.
  

  

   

Dense materials will, however, readily transmit impact noise. Composite construction using combinations of light and heavy mass materials are best to reduce noise transmission.

 

Doors and windows

Doors and windows must be effectively sealed. Ventilation and services openings in walls and ceilings are critical contributors to sound transmission. For example, switches and power outlets should never be back to back in walls that need high acoustic ratings (such as multi-residential buildings). Rather, they should be in separate air spaces on either side of a stud or noggin.

A 3mm single glazed window has a very low Rw, and windows can let in a lot of noise, open or closed. The potential sound reduction from a highly insulating wall can be substantially reduced by poor window design.

Double glazing and laminated glass are both effective at reducing noise, provided the windows are closed and the frames are well sealed. The following table shows the percentage noise reduction compared with 3mm glass. Note that thicker glass generally does not improve thermal insulation. For a combination of sound and thermal insulation, use double glazing.

Bear in mind that the acoustic insulation of any window is severely compromised when it is open. To maintain effective ventilation with doors and windows closed, consider installing acoustic wall vents which are designed to provide ventilation while minimising noise transmission.

Noise reduction for glazing compared with 3mm glass

Glazing type		Voice noise reduction (percentage)	Traffic noise reduction (percentage)
Single	6.38mm laminated		24
	10mm glass	24	38
	10.38mm laminated	29	43
Double	4mm/12mm space/4mm	19
	10mm/12mm space/6.38mm laminated		46
	10mm/12mm space/6mm	34
	6mm/100mm space/4mm		57
	6.38mm laminated/8mm space/4mm	46

Source: Pilkington

Specifications

Good design detail and construction practice is critical to the performance of both heavyweight and lightweight construction.

• Pay attention to building components such as floor and ceiling plates and to the installation of services such as plumbing and power outlets; insulate them acoustically if necessary to ensure the desired performance is achieved.
• Avoid locating plumbing and waste pipes close to quiet rooms or ensure that they are adequately soundproofed — a range of sound insulation products exists for plumbing and waste pipes in walls and floors.
• Provide extra sound insulation for noisy rooms such as laundries. Use acoustic mounts or pads for clothes washers and dryers.
• Use built-in robes as sound buffers between bedrooms.
• Use solid core doors which are more effective sound insulators than hollow core.
• Use door closers or foam or plastic strips on door frames to stop doors banging.
• Reduce sound reflection transmission through gaps with draught sealing strips.

 

 

• Australian Building Codes Board (2019). Part 3.8.6 Sound insulation.
• Anderson L, Mulligan B and Goodman L (1984). Effects of vegetation on human response to sound. Journal of Arboriculture 10(2):45-49.
• Gyrpock (2017). The Gyprock red book, North Ryde, NSW.
• National Institute on Deafness and Other Communication Disorders, Noise induced hearing loss.
• NSW Environment Protection Authority, Noise.

Learn more

• Explore Materials for more ideas on the structure of your home
• Read Designing your home to find out what to consider when you are starting out
• Review Renovations and additions to discover how you can upgrade your home to be more comfortable and energy-efficient

Authors

Original author: Geoff Milne

Contributing authors: Kendall Banfield, Chris Reardon

Updated: Paul Downton 2013