New noise control technology in a London transformer station
In the heart of London, the transformers of a power distribution station could be heard by local residents. Merford installed an acoustic screen with the NoiseTrap® technology developed by Sonobex. A revolutionary metamaterial technology where sound is passively cancelled in the panel and natural ventilation is also possible. Network operator UK Power Networks was the first to successfully use this technology for the substation in the Bayswater district, London.
UK Power Networks
Transformers produce low-frequency noise that can sometimes be heard by local residents. These tones are normally difficult to reduce and require heavy acoustic measures to shield the sound, which is why natural ventilation is usually not possible. Sonobex, part of Merford since 2017, has developed a technology that attenuates low frequencies and also allows natural ventilation. The patented* technology was put into practice for the first time at a substation in London.
The four transformers that caused inconvenience in London are housed in concrete compartments with an opening for natural ventilation on one side. The project involved the installation of acoustic barriers to close the compartments and stop the noise from escaping. It was necessary that the solution not only offered acoustic mitigation, but also provided sufficient ventilation for the cooling of the equipment.
Analysis and design
A detailed computer model was developed to study the acoustic environment, in addition to a fluid flow analysis of the heat convection. The computer models were used to optimise the design of the barrier for both characteristics.
The solution, an acoustic panel with large open slots, was designed by Sonobex and manufactured by Merford. The acoustic screens are made up of modular panels, some of which are designed as doors to provide access to the equipment for maintenance purposes. It was installed by PES (UK) Ltd. who has over 30 years of technical experience in worldwide installations and project management. After the completion of the installation, noise surveys confirmed that the solution is performing as predicted and that the noise levels are now below World Health Organization Guidelines.
John Nagle, senior project manager at UK Power Networks, said: "It was very exciting to work on a project that has delivered a solution that has not been used anywhere else in the world. Our stations are often close to the location of our customers, so they can supply electricity to households and businesses, but very occasionally the equipment can be heard by local residents. We want to be a good neighbour and keep the disruption to a minimum. The screens offer a new option for us to use, in the rare cases where some operating noise can be heard outside of our sites".
UK Power Networks will now see if the screens are suitable for other sites where equipment can be heard. Other parties have also expressed interest in this solution to reduce noise from transformers.
* Patents: US 8789652, US 9607600, EP 2394266.
Patent Pending: US 15 / 509,360, EP 14707832.3, EP 15718253.6, EP 16189799.6