Beefing up the sound barriers

'Noise' a source of pollution. Photo / Getty Images

Sound proofing standards for apartments have improved in leaps and bounds. Apartment buyers in the 1990s and 2000s often found they could almost hear their neighbour's conversations. When you live with neighbours on two sides, above and below, that can be a lot of noise.

Sound can travel through walls and floors or be generated from central waste water, plumbing, air-conditioning, lifts, common corridors, noisy business activities and more.

Poor acoustics in an apartment can have health and psychological effects, as well as impairing cognition, according to the New Zealand Green Building Council. (NZGBC).
Internal noise has been recognised as a health hazard by the World Health Organisation (WHO).

The good news in New Zealand is that sound proofing is better in newer builds.

Clause G6 of the New Zealand Building Code regulates sound insulation in new builds, says Dave Robson, manager building performance and engineering at the Ministry of Business, Innovation and Employment (MBIE).

It dictates the minimum airborne and impact sound insulation performance between abutting properties such as apartments and terraced houses.

"New Zealand uses STC (sound transmission class) and IIC (impact insulation class) rating," says Robson. "In both cases the Building Code includes a minimum of 55 on a scale of 1 to 100."

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The Building Code requires a minimum frequency weighted sound/noise reduction between adjoining spaces of 55 decibels.

In some cases district plans may also require higher standards. If, for example, you live in an especially noisy area, such as downtown Auckland, the district plan may also have external sound insulation requirements so you hear less from outside when your windows are closed.

Acoustic performance has a number of factors to consider, including building geometry, construction materials, workmanship and the amount and type of absorptive material such as wall linings and furnishings, says Robson.

MBIE figures show that New Zealand standards for airborne sound insulation are higher than almost all European countries: equal to that of Austria and Finland and only beaten by Scotland.

In terms of impact sound insulation between dwellings, New Zealand is in the middle of the pack compared to 35 European countries, beating many high hitters such as Switzerland, Iceland, Germany and Denmark. The leaders according to the data from MBIE are Croatia, Serbia and Spain.

Apartment buyers looking for peace and quiet ought to consider the level of insulation. MBIE recommends R1.8 thermal insulation.

Sound can also be reduced by the use of additional internal linings to the walls, ceiling or both. Likewise double-glazed windows with air gaps between the panes offer better sound insulation than laminated windows.

There are many tricks that architects can use to reduce noise, such as avoiding installing services on adjoining walls, applying perimeter seals to doors and windows to avoid sound leakage, and allowing sufficient thickness between adjoining walls and also floors and ceilings.

The building can also be laid out to position noisy services away from the quieter parts of dwellings, and mount appliances and design ductwork to reduce noise.

Both the household appliances supplied in the home and the fans and impellers in the building should be chosen for their quietness. Typically the more expensive the development, the better the sound proofing design and implementation.