Designing for Quiet

AS DWELLING density increases, building occupants often become more aware of noise, that is, any unwanted sound the occupant cannot control.

For building designers, key areas that need consideration in the design of dwellings are:

  • inter-tenancy noise – from adjacent dwellings and neighbours

  • environmental noise – street or building-generated noise, such as traffic, exuberant people, night clubs and bars, night street works or construction

  • building services noise – air conditioning, heat pumps, drainage, plumbing, lifts.

Noise can impact health

Excessive noise levels can significantly affect the amenity of a dwelling and the health and wellbeing of its occupants. Some suffer from misophonia, also known as selective sound sensitivity syndrome, where a common noise causes anxiety or anger.

Other factors that influence how we perceive noise are:

  • frequency – low-frequency noise (10–200 Hz) is more intrusive and harder to mitigate

  • volume

  • time – how long the noise persists

  • inability to influence generation of the noise

  • distance – how far away the noise source is

  • tolerance – tolerance of noise may decrease as housing density increases

  • age – we become more aware and possibly less tolerant of noise as we get older, particularly low-frequency noise

  • desire for reasonable acoustic privacy, particularly with the closer proximity of neighbours

    Main types of sound transmission

    There are generally two types of sound transmission to consider:

    • Airborne transmission – noise originating in air, such as voices, music and vehicle traffic.

    • Impact transmission – noise originating directly on the structure by blows or vibration.

    A third type, known as flanking transmission, is any sound transmitted to the receiver but not directly through the separating element. These indirect or flanking paths between source and receiver are harder to predict and can often significantly affect acoustic performance.

    For example, consider the sound carried via a duct or common ceiling space between two adjacent rooms, adjacent windows in adjoining tenancies or transmitted via a common floor slab. Even if the wall directly between the rooms transmits no sound, some noise will still be heard in the receiving room via these flanking paths.

    Airborne and impact transmission is usually made up of sound travelling via direct and flanking paths.

Reducing internal noise impact

To reduce noise transmission within the dwelling, the designer can:

  • place buffer rooms between noise sources and quiet spaces

  • add acoustic insulation and greater mass to internal walls (for example, specify them as acoustic-rated walls)

  • separate or shield windows in adjacent tenancies

  • specify sound-absorbing surface finishes to reduce reverberation within spaces

  • physically separate solid components to minimise the conduction of vibrations

  • use a heavy fabric for window drapes

  • install seals on all doors and any unsealed windows

  • use solid-core doors

  • avoid the need for air conditioning at quiet times

  • locate plumbing and wastepipes away from quiet rooms or ensure that they are adequately soundproofed, and insulate any ducting

  • use built-in wardrobes as sound buffers between bedrooms

  • use soft and absorbent furnishings.

Reducing external noise impact

There are several options to minimise the impact of external noise. However, there are also drawbacks associated with most of them.

Windows can be designed to minimise noise transmission, but all benefit is lost when the windows are opened. Using thicker glass or insulating glass units designed to reduce heat loss also reduces sound transmission.

To maximise noise mitigation through the external envelope, the designer can:

  • use walls that incorporate mass, such as concrete or concrete masonry construction (doubling the mass of a wall increases the STC rating by 5–6 dB)

  • specify smaller windows in walls that face noise sources

  • add noise control insulation, separate or stagger stud construction or use a proprietary acoustic-rated wall construction system in lightweight framing (adding insulation within a wall or floor/ceiling cavity will improve the STC rating by 4–6 dB).

Reducing noise transmission by 10 dB is roughly equivalent to halving the perceived loudness of the sound coming through the wall, over a range of low frequencies.

For stand-alone dwellings and low-level buildings, consider:

  • constructing heavy fences between the building and sources of noise

  • earth bunding if there is sufficient space

  • locating spaces that require quiet away from the street.

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