Environmental Noise

Mitigation Measures

The following shows some mitigating measures for some types of environmental noise.
Subsequent sections will provide details and examples of some of the above mitigating measures. Follow the text or alternatively click the icon next to a mitigating measure to access to details on it.

(Click on the above headings to link to corresponding sections below)

Land Use Planning
One important planning tool to minimize the impact of environmental noise is to ensure compatibility of different uses adjacent to each other. Outline Zoning Plans (OZPs) are drawn under the Town Planning Ordinance to govern land uses for different purposes.

For any amendment of existing OZPs or drafting of new OZPs, implications on the environment including any possible noise impact will be addressed.

The aerial photo below illustrates how land use planning provides separate zones for the industrial undertakings at the Tai Po Industrial Estate and the residential buildings in the nearby housing estates to avoid incompatibility in land use. A buffer area for non noise sensitive use between the two zones can further help to reduce noise impact to the residents arising from the industrial operation.

Image of buffer area reducing noise impact from Tai Po Industrial Estate to the Tai Po residents

Alternative Siting / Alignment
One most effective way to deal with noise is to plan away the problems by selecting alternative site or alignment that avoids serious problems.

If a certain locality is found to be unsuitable for the development of a certain noise sensitive use or a certain noise source due to adverse environmental noise impact on existing sensitive development, then an alternative location or site may have to be explored. Similarly, noise impact from road traffic can be minimized through suitable choice of alternative alignment. The following plan shows the various proposals of the Tseung Kwan O Western Coast Road. Please click on the demo button to read the details.


The original design, shown in red, employs elevated roads running along the coastal areas. This scheme might expose noise sensitive uses to excessive traffic noise and noise barriers or enclosures might be required to improve the situation.

A number of alternative proposals have been put forward and they are being evaluated at the time this Package is being prepared. All these alternative proposals employ tunnels which, among other consideration, can help to design out traffic noise impact on the nearby noise sensitive uses.


Screening by Noise Tolerant Buildings
This is an illustration of how a noise tolerant building such as a multi-storey carpark building is used to protect residential buildings from road traffic noise. Placing a noise tolerant building in between the road traffic and the residential building causes the noise in the "shadow zone" to be reduced. This brings about a reduction in the traffic noise affecting the residents. Please click on the demo button to read the details. Then click on the stop button to stop the sound/demo.


This concept has been employed in the design of the Hong Keung Court, Lok Fu to protect its residents from traffic noise from the Fung Mo Street, as generally illustrated by the following plan and photographs:

Building Disposition
The impact of environmental noise can also be reduced by the proper disposition of noise sensitive buildings within a development.

The following plan shows residential blocks in blue and the Sai Sha Road as the major noise source in yellow. As shown, the residential buildings are sited away or set back from the Sai Sha Road as far as possible. (The development also employs noise barrier to reduce the impact of traffic noise. The issue of noise barrier will be discussed later. Follow the text or click here to jump to the part on barrier .)


Decking Over
This illustration shows how the use of decking over reduces impact of road traffic noise on a number of residential buildings. Please click on the demo button to read the details. Then click on the stop button to stop the sound/demo.

One such example in Hong Kong is the Sceneway Garden at Lam Tin, as shown by the following plan and photographs:

Podium
Putting residential buildings on top of a podium can provide shielding against traffic noise from roads in their vicinity, as illustrated by this animation. Please click on the demo button to read the details. Then click on the stop button to stop the sound/demo.

The development at Island Place, North Point uses this measure to reduce the impact of traffic noise from the busy King's Road on the residents.

Noise Barrier/Enclosure
Noise Barrier

A noise barrier or acoustic shield reduces noise by interrupting the propagation of sound waves. With proper design and selection of material for the noise barrier or acoustic shield, noise reaching a noise sensitive receiver would be primarily through diffraction over the top of the barrier and around its ends.

The acoustical "shadow zone" created behind the barrier is where noise levels are substantially lowered.

To function well, the barrier must prevent the line-of-sight between the noise source and the receiver.

Effective noise barriers can reduce noise levels by as much as 20 dB(A).

The following are some common types of noise barriers used in Hong Kong.
Please click on the demo button to read the details. Then click on the stop button to stop the sound/demo.

(a) Vertical Barrier

(b)
Cantilever Barrier

The following table shows some examples of barriers erected in Hong Kong. Click on the mimic diagrams to see more details :

Project Characteristics Mimic Photographs
Vertical Roadside Barrier
for Route 5 - Shatin Approach near Mei Lam Estate
  • Simplest form of noise screening structure
  • Effective in protecting low-level sensitive receivers
  • Can be installed on one side or both sides of carriageway
 
Vertical Roadside Barrier for Route 5 - Shatin Approach near Mei Lam Estate
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Cantilevered Barrier
for West Kowloon Expressway - near Lai King
  • Effective in protecting low to mid-floor sensitive receivers
  • Can be installed on one side or both sides of carriageway
Cantilevered Barrier for West Kowloon Expressway - near Lai King
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Central Barrier
for West Kowloon Expressway - near Mei Foo Sun Chuen and Nam Cheong Estate
  • Vertical barrier installed located in the central reserve of dual carriageway
  • Effective for protecting low to mid floor sensitive receivers from wide dual carriageways
Central Barrier for West Kowloon Expressway - near Mei Foo Sun Chuen and Nam Cheong Estate
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Noise Enclosure

To function well, a noise barrier must prevent the line-of-sight between the noise source and the receiver. This is not always possible, especially with high-rise noise sensitive uses. In this circumstance, noise enclosures are required to provide appropriate protection against environmental noise for the noise sensitive uses.

In general, an enclosure can reduce noise by more than 20 dB(A).

Similar to noise barriers, noise enclosure should be designed to serve both acoustic and aesthetic purposes.

The following are some common types of noise barriers used in Hong Kong.
Please click on the demo button to read the details. Then click on the stop button to stop the sound/demo.

(a)
Semi-Enclosure

(b)
Full Enclosure

The following table shows some examples of enclosures erected in Hong Kong. Click on the mimic diagrams to see more details :

Project Characteristics Mimic Photographs
Semi-enclosure
for Tate's Cairn Tunnel Approach at Choi Hung Estate and Richland Gardens
  • Effective in protecting high-rise sensitive receiver at one side of the carriageway
Semi-enclosure for Tate's Cairn Tunnel Approach at Choi  Hung Estate and Richland Gardens
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Semi-enclosure for Tate's Cairn Tunnel Approach at Choi  Hung Estate and Richland Gardens
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Full Enclosure
for Wong Chu Road
  • Effective in protecting high-rise sensitive receivers located on both sides of carriageway
Full Enclosure for Wong Chu Road
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Architectural Features/Balcony
Certain architectural features such as fins and balcony can help reduce impact of road traffic noise on residential buildings.


Image of using architectural fins to reduce road traffic noise impact

Image of using balcony to reduce road traffic noise impact

Building Orientation and Innovative Layout
The following illustration explains the idea of using building orientation and innovative layout to reduce the impact of traffic noise :

Image of using innovative layout to reduce road traffic noise impact

In such a design, the building is oriented so that less noise sensitive uses such as kitchen, bathroom and store rooms are located to one side of the flat while noise sensitive uses such as living rooms and bed rooms are located on the other side. The building is so oriented that the side of flat containing less noise sensitive uses is facing the major noise source such as a busy trunk road. This building arrangement can sometimes help to render sensitive development at an otherwise "environmentally unacceptable site" acceptable.

Open-Textured Road Surfacing
There are two main sources of noise from vehicles: the engine and road/tyre interaction.

When traveling on level roads and at high-speed traffic, road/tyre interaction noise dominates. On inclined road or level at low-speed traffic, engine noise becomes dominant.

Most roads are paved with surface that has microscopic grooves which cause the noise to resonate, thereby increasing the noise. But a different material on the road will reduce the noise arising from road/tyre interaction.

Friction course, a special type of bituminous highway surfacing, was originally designed to improve skid resistance by virtue of its open texture. The open-textured bituminous highway surfacing consists of tiny holes making up 20% of the volume and can reduce traffic noise induced by the interaction between road surface and vehicles tyres of high-speed traffic by up to 5dB(A). Please click on the demo button to see the details.


Photo of open texture materials

Acoustic Insulation of Receiver
The provision of window insulation and air-conditioning is the "last resort" in an attempt to abate the residual impact from noise sources not controlled under the NCO, such as aircraft, road traffic and helicopter.

The acoustic insulation will practically deprive the receivers of outdoor activities and an "open-window" life style. While acoustic insulation is commonly found in some western countries, the warm and humid climate in Hong Kong makes it more expensive for noise sensitive uses due to the need to provide air-conditioning for a "closed-window" environment.

The suitable window types for noise insulation are shown in the following table. The table indicates the suitable window type that should be used when the estimated noise level will exceed the relevant standard by ß value.


Table of window types summary

A typical example of this measure is the School Insulation Programme. For details of this programme, please click here.

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Noise Mitigation



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