Reducing noise

Why reduce noise?

Sound insulation of residential buildings plays a key role in maintaining people’s wellbeing.

The amount of noise in and around a home will differ, depending on the building’s location, design, construction and type – detached house, townhouse, multi-unit complex or apartment building. Noise can be a major issue for people, especially if there isn’t enough sound insulation between properties.

Requirements

In New Zealand, sound insulation regulations for new buildings are specified in clause G6 of the New Zealand Building Code. These regulations dictate the minimum airborne and impact sound insulation performance between properties that touch each other – side to side, above and below (called abutting residential tenancies). Some people may prefer to exceed the Building Code requirements for better sound insulation.

Building Code Clause G6 has more information.

Depending on where you live, your council may have additional external sound insulation requirements in the district plan, for example, if your house is in a particularly noisy area.

You can check with your local council for additional external sound insulation requirements by talking with one of their planners.

Property owners also have an obligation under the Resource Management Act to avoid making unreasonable or excessive noise.

This section will tell you what to look for concerning noise and sound insulation, whether you’re buying or renting, renovating or building new, and what you can do to reduce noise around your home.

What to look for when buying or renting

When you're looking at buying or renting a property, ask the real estate agent or landlord questions about the noise of the surrounding environment. You should also pay attention to noise while you are looking around. Think about the time of day, noise level and types of neighbourhood noise as well as the building’s design in relation to internal and external noise.

Controlling noise is often a trade-off with other priorities, and your decisions may depend on what you are willing to put up with. It might also be useful to know what you can and can't change – sometimes the design of a property can mean there is not a lot that can be done to reduce some noise.

If you can, look at the house at different times of the day. Try to visit when there are just a few people present as well as in the middle of a busy open home.

Try to find out:

• How close are you to your neighbours?
• What’s the noise like with doors and windows open?
• What noise sources may be present? (You may not want to be shut inside in the middle of summer trying to block out neighbourhood noise.)

Common external noise sources

• heat pump outside units, which can be quite noisy – whether it’s yours or a neighbour's
• swimming pools, spas or hot tubs can be loud (noise typically comes from pumps and can be ongoing)
• kitchen extracts (including the neighbour's)
• non-residential neighbourhoods or thoroughfares, including central business areas, high traffic volumes, port or airport, trucks, trains, bars, restaurants, commercial neighbours, churches, sports fields, childcare centres and schools.

Common internal noise sources

• central waste water or plumbing
• central air-conditioning
• lifts
• a gym or movie theatre
• common corridors – you'll need to use a lobby to deal with loud noises from corridors as a door won't block out all the noise from a corridor)
• noisy businesses or activities in mixed use developments (for example, a bar or gym under an apartment building)
• in flatting situations or family environments you need to think about how you will use a space and if these activities will be affected by the noisy use of a neighbouring space.

Insulation

Is there fibre-based insulation in external and internal walls, roof cavity and floor? You could ask the agent or landlord if the house has been sound insulated or if it was designed to deal with any particular noises.

If you're getting a professional to do a building inspection of the property, this might involve them inspecting wall, floor and ceiling cavities and looking at the wall or floor structure, linings, insulation, glazing, materials and detailing. If you had serious concerns, an acoustician could measure the sound insulation.

Fibre-based insulation includes materials such as wool, fibre glass and polyester. Having fibre insulation in wall, floor or ceiling cavities can significantly improve sound insulation. This should have a minimum density of 9.8kg/m³.

There is little acoustic benefit in using greater density insulation. For the same money, you will probably get greater sound insulation performance by adding additional internal linings to your walls, ceiling or both. However, you will need to get a building consent before modifying an inter-tenancy wall.

Rigid foam insulation like polystyrene can be good for thermal insulation but is acoustically transparent (it doesn’t reduce noise). In some cases, having polystyrene installed is worse for sound insulation than an air gap.

Floors

Consider whether the floors are ‘bouncy or drummy’? If the property is multi-storied, get someone to move around upstairs while you listen below. Is this noise going to upset your sleep, relaxation, conversations, TV watching or enjoyment of the space below?

Windows

Are the windows double-glazed or laminated? Generally, the thicker the glazing and the bigger the air-gap between panes, the better the sound insulation of the window.

Double-glazing provides a small improvement for reducing mid and high frequency noises, but if the property has low frequency noise, such as from planes and trucks, etc, talk to an expert for advice (acoustician) as double glazing may not be the best solution.

Are there gaps around door and window openings? Minimising gaps and having effective seals will help control high frequency noise problems.

Plumbing

Can you access the plumbing? If so, this will give you the option to lag the pipes. This involves wrapping them in a heavy layer, typically mass loaded vinyl with a minimum surface mass of 4kg/m². Foam can be good for thermal insulation but not for reducing noise.

Make sure there are no 90 degree bends (water will hit the corner noisily rather than run smoothly along curves).

If you can't access the plumbing try turning on a hot tap and running the shower. Is this noise disruptive?

Air-conditioning

Wait until the space is relatively quiet and run the air-conditioning to see if the noise level is acceptable.

Multi-units, townhouses or cross-leases

Consider how close driveways and common walkways are to quiet areas, such as bedrooms. Is this going to be a problem for you?

Is the property a multi-unit building older than 1991? If so, it wouldn't have needed to meet the sound insulation requirements of the New Zealand Building Code for sound insulation between units when it was built (although this might have been done anyway). Even if it does, it may not be enough for your requirements, so check it out if you can.

Is it a former retail or commercial property, converted into a residential property? If it was a retrofit rather than a new build, it might not meet the sound insulation requirements of the New Zealand Building Code. Check the council's property file or ask the real estate agent what level the sound insulation was designed to achieve (ask for actual numbers and compare these to the current Building Code requirements)

Are there noise rules? Some potential acoustic issues are easier to deal with if they are covered in a body corporate rule (or similar). For example:

• Can anyone replace their floor covering with whatever they want, including going to bare floorboards without notification?
• Are speakers allowed to be connected to common walls or the building structure?
• Will these rules limit your activities too? Think about whether you are comfortable with those controls.

Design to reduce noise, whether building new or renovating

If you're building a new home, you have an opportunity to get it designed in a way that works well acoustically, keeping external and internal noise to a minimum. If you're renovating, you may be able to make some changes that will reduce noise as well.

As a general rule, the more mass, the better the sound insulation. Mass can be increased by using a thicker version of the same material or using a more dense material.

External noise

Think about your likely noise sources and design to reduce their effect. Different noise frequencies need different approaches. If you have low frequency noise sources or unusually loud sources, call an expert (acoustician).

Fencing

Fencing can block some noise, but you need to block any view of the noise source in order for the fence to be effective. If you can still see the noise source, the fencing won't work. For the fence to work it also needs to be solid. That means the fence needs to be made from a reasonably dense material that is greater than 25mm thick, and have minimal gaps.

Roofs and walls

Pitched roofs generally only need fibre-based insulation. If you have unusually loud sources you may need extra internal lining or sarking.

Skillion roofs need extra internal linings or suspended ceilings if you want good sound insulation.

If your house has sarking in the walls, roof or ceilings try to keep it – it improves your home's sound insulation.

Windows

Windows and openings are typically the weak point of a house’s sound insulation, so deal with these first. Generally for windows, the thicker the glazing and the bigger the air gap between panes, the better the window's sound insulation. Double-glazing is slightly better than single glazing for sound insulation. However, double-glazing is not always better for low frequency noise such as planes and some traffic. Also, check that the seals around the windows are intact and seal effectively. If you have low frequency noise sources, call an expert for advice (acoustician).

Insulation

Fibre-based insulation is your sound insulation friend. Put it in the cavities of walls, roof and floors (for example, external walls around quiet areas, bedrooms, etc, or spaces that are generating noise, eg bathrooms, cavities that have plumbing, etc). Before you insulate, check how to do it properly and safely by reading the Standard Installing bulk thermal insulation in residential buildings.

NZS 4246:2016 – Installing bulk thermal insulation in residential buildings on the Standards New Zealand website has more information.

Orientation and location

Orientation and location of living spaces is important – try not to put quiet areas next to sources of loud external noise. This can be harder to change as part of a renovation, but is something to consider.

Mechanical services should be located away from quiet areas (for example, fans, heat pump units, kitchen extracts, plumbing, etc). Also think about your neighbours when deciding locations for any outside units.

Internal noise

As well as insulating you from external noises, fibre-based insulation can be used between quiet and noisy spaces. For example, between bedrooms and bathrooms, lounges and kitchens (try to insulate near the noisy source rather than in the quiet space, noise is more easily controlled at the source than at the receiver).

Multi-storey houses

In two-storey housing or multi-units think about the upstairs flooring:

• Don't have hard surfaces above spaces you want to be quiet
• Use a sound/impact absorbent underlay under your floor surface
• Noise from creaky floor boards might be reduced by:
  • making them stiffer – rescrew and/or add more screws
  • putting fibre-based insulation in the ceiling void below the boards
  • installing a suspended ceiling system in the first storey.

Quality sound/impact absorbent underlay can significantly improve the impact sound insulation between floors, but this can increase the cost. When buying underlay you need to consider what is going on top of it and always follow the manufacturer's instructions around adhesives (cheaper or inferior adhesives can cause problems and compromise the underlay's effectiveness).

Plumbing

Vibration-isolate plumbing pipes, so you won't hear the sound of water running throughout the house. That means:

• using rubber isolation mounts, rather than rigidly fixed pipes
• making sure pipes don't sit hard up against the building's structure so they don't transmit noise/vibration into the building structure
• avoiding 90 degree pipe bends (water will hit the corner noisily rather than run smoothly along curves).

Methods to reduce noise

1. Acoustic fibre-based insulation.
2. Maintain clearance between pipes and structure to minimise vibration.
3. Use rubber strips to minimise the vibration transmitted. The rubber should have a minimum surface mass of 4kg/m² and prevent the clips touching the pipe work.

Location of spaces and appliances

If you are changing spaces around or extending the house, think about room locations – noisy areas should not go next to/above/below quiet areas unless you are going to specially design for extra sound insulation.

As with external considerations, think about where your mechanical services are located (for example, fans, heat pumps, kitchen extracts and plumbing).

Isolate stereo speakers, unless you want to hear your music in every part of your home. That means:

• don't fix your speakers to the building's structure – use rubber isolation mounts
• don't have speakers hard up against internal linings