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A new noise barrier installed on a busy stretch of the A12 in Bromley-by-Bow, east London is an acoustic shield and a public artwork.
Installation of the barrier marks the first UK external use of a “silk metal” system, which also incorporates a striking sculptural design that draws inspiration from nearby waterways.
The design and construction team was led by architect Beep Studio, in collaboration with consultancy Expedition Engineering, manufacturer Cake Industries, acoustic consultant Echo Barrier, and engineering firm Power & Line.
The innovative acoustic baffle has been designed to enhance the public space for people walking and cycling in the area.
Noise levels on the A12, which is used by 15M vehicles every year, have been found to consistently exceed 78 decibels by the University of East London (UEL). This puts the road in the most severe category for noise pollution.
While most acoustic treatments reduce noise by using soft or textured surfaces to absorb vibrations, the silk metal system is intended to work differently.
An aluminium sheet perforated with tiny holes less than 1mm in diameter forms the front face of a closed box. As sound waves hit the sheet it starts to vibrate, forcing air trapped in the box through the perforations. The resulting friction slows the passage of air, which in turn reduces the vibration of the sheet, muting the echoing and reverberating sound.
The barrier is formed from over 60 of these sealed cassettes, all of which absorb noise generated by the road through friction, ultimately dissipating this sound energy as heat.
Each cassette in the assembly is linked together into larger groups, which in turn are mounted to an articulated concrete footing. These footings require no permanent fix to the highway and can be removed through a simple crane lift.
Transport for London director of network management Glynn Barton said: “Our road network plays a vital role in keeping people and goods moving across the capital, but we know that noise from motor vehicles can have a major impact on people moving through the area.
“Our investment in this innovative new noise barrier will make the area a quieter and much more pleasant environment for people walking and cycling along the A12 in Bromley-by-Bow.”
The 30m long barrier reaches a peak height of 3m in front the Jefferson Plaza housing development, where the acoustic effect has the greatest impact.
Noise levels, pollution levels and public perceptions of the installation will be monitored by the UEL. Should the project prove successful, a larger product roll out is possible, subject to further testing.
Barrier design
The barrier includes 63 uniquely folded aluminium cassettes, fabricated to form the backbone of the barrier. A parametrically defined computer model was created to automatically generate the bespoke cutting patterns needed for each cassette.
The simple structural solution designed by Cake Industries enabled the flowing geometry to be generated from laser cut pieces, and careful consideration of adjustability and tolerance allowed these cassettes to be bolted onto concrete footings sitting on the pavement.
The cassettes form a mould that was clad in “silk metal”. An extensive series of prototyping and testing was used to prove the concept, before the design was signed off for manufacture. The fabrication design and assembly was considered carefully to maximise quality and repeatability, and is now set up for future iterations of the scheme.
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