It’s not uncommon that sites close to major highways and rail lines have been identified or rezoned for public housing, in an all-out land hunt to provide subsidized homes for the 300,000 applicants currently on the waiting list.
Acoustic windows are among the various measures adopted by the Hong Kong Housing Authority to mitigate the impact of traffic noise at its developments.
Owing to scarce land resources in Hong Kong, the availability of sites for public housing development is limited in urban areas and some of the public housing developments in these areas are inevitably affected by road traffic noise.
“In this regard, the HA has to consider various noise mitigation measures during the planning and design stage, including appropriate disposition of building blocks and installation of noise barriers, architectural fins and acoustic windows,” a Housing Authority spokesman said.
The authority spent two years, in collaboration with local research institutes, to develop a specially designed acoustic window for sound insulation in residential buildings. These windows have been installed in units at King Tai Court, close to Prince Edward Road East, a major east-west thoroughfare in San Po Kong, as a trial scheme.
Such an acoustic window is a modified double-glazed window that comprises two layers: an openable window at the outer layer and a sliding window at the inner layer.
Unlike conventional double-glazed windows, the two-window-layer design allows an opening for ventilation. Noise absorbent material is installed between the window layers to enhance noise reduction. The distance, size and positioning of the opening are carefully designed with reference to noise refraction and reflection behavior to ensure that the acoustic window can reduce noise while also maintaining ventilation as well as natural lighting at the same time.
The acoustic window can reduce noise even when the window is not completely closed, as proven in tests conducted by the authority in mock-up roadside flats, achieving noise attenuation of up to about eight decibels while allowing air circulation.
“These acoustic windows can effectively mitigate the traffic noise impact on public housing units. We will consider adopting acoustic windows in other public housing developments affected by traffic noise,” the spokesman said.
Furthermore, the authority has been adopting case-based, individually designed floor plans for blocks in close proximity to major roads to reduce the impact of noise pollution.
For instance, communal and service facilities such as lifts, staircases and garbage chambers on each floor are clustered on the side facing the nearby East Rail Line in blocks at the newly finished Po Heung Estate in Tai Po and Fung Wo Estate in Sha Tin, while all homes are arranged on the other side to ensure minimum noise exposure for tenants.
Load bearing walls, usually thicker than other non-structural walls, as well as elevator and ventilating shafts are also built on the sides facing the source of noise to serve as a buffer. Sound-absorbing bricks, façade, doors and other decoration and coating materials are used for units that may still be affected by noise.
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