Quiet confidence: custom-attuning acoustics on the Sydney Metro

Pyrotek Sydney Metro custom-attuned noise vibration mitigation

On 26 May, the first stage of Australia‘s largest public transport project was opened; the Sydney Metro Northwest. The immense project demanded unique specifications for noise minimisation and required an innovative solution. Combining locally-supplied resources and global knowledge, Pyrotek custom-built a new material with the requisite properties.

Running from Rouse Hill to Epping, Sydney Metro Northwest includes a 4km elevated skytrain, a 270m cable-stayed bridge, and twin 15km tunnels — the longest constructed in Australia.

To ensure passenger comfort and safety, the tracks and walls of these tunnels had to be lined with an absorbing material to reduce reverberation created by wheel–rail impact. The materials had to meet three specifications:

Noise level: when operating in the tunnels, noise within passenger areas of carriages had to be a maximum of 78 dB(A)

Non-combustibility: to ensure a fire safe environment, it was crucial the material would not emit smoke or toxic fumes in the case of an emergency

‘Trafficability’: with the area around the tracks made a designated pathway, materials needed to be ‘trafficable’, i.e. durable enough to be walked on during an emergency or routine maintenance

Developing a custom solution

Pyrotek secured the contract to develop the required material for track absorption and tunnel walls, working alongside Northwest Rapid Transit (NRT), which was awarded the operations, trains and systems contract.

Finding a material for the tunnel walls was straightforward. Having been applied in tunnel projects worldwide, Reapor had a track record of reliable noise mitigation. Manufactured from recycled glass, the material is completely non-combustible.

Developing a track absorber for the area on the tunnel floor, however, posed a unique challenge. Even with more than 40 years’ experience developing noise control solutions, Pyrotek had never encountered a need for ‘trafficable’ material. Materials applied in the past lacked the composition and vitreous strength required for the Sydney Metro tunnels.

In response, Pyrotek’s technical team engineered a new material with the correct properties, performing tests in the company’s reverberation room alongside independent facilities.

Engineers were able to ‘attune’ the material to target the specific frequencies associated with the noise challenges experienced, facilitating optimal acoustic absorption. The material was customised to Sydney Metro to reduce noise from moving trains.

The resulting product, Viterolite 900, is a durable concrete-like material with high impact resistance, a broad range of frequency absorption and 100 per cent non-combustibility. Viterolite and Reapor panels also reduce the radiation of sound at tunnel openings, lessening community impact.

In aiming for compliance with acoustic and design specifications, the materials actually exceeded expectations, reducing tunnel noise levels to under 78dB(A). Results are expected to further improve as the rail tracks flatten.

Pyrotek Sydney Metro custom-attuned noise vibration mitigation

Manufacturing in a time limit

A new plant and equipment were designed to locally produce the large volume of custom-sized panels required. Pyrotek upscaled manufacture capacity to cast over 100 tonnes of material each day.

As the Australian manufacturing branch of the global company, Pyrotek was able to combine the convenience of local materials supply and innovation (easier transactions, better responsiveness) with global knowledge resources, logistics and capital strength.

Simon Tibbet, NRT Area Manager, said being local and flexible made Pyrotek invaluable to logistics and installation.

“Their ability to meet the delivery program for the panels was critical to NRT completing this project on time,” Mr Tibbet said. “The final outcome far exceeded our expectations.”

By developing the capacity to test and custom-attune its products’ acoustics, Pyrotek surpassed the benchmark for passenger comfort and safety criteria in noise mitigation.

This partner content is brought to you by Pyrotek. Working in Australia and internationally to develop innovative noise mitigation solutions, Pyrotek has been specified by the world’s leading acoustic consultants. For more information, visit pyroteknc.com

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