Hospitals to test noise-cancelling metamaterial

A metamaterial capable of bending, shaping and focusing acoustic waves is to be trialled in hospitals and other locations where noise is problematic.

Dr Gianluca Memoli and portable sound blind (Image: Metasonixx)

The so-called Sonoblind panel technology will allow scientists to turn plastic sheets into noise-cancelling panels with the same noise-reduction effect of as two inches of plywood but weighing four to six times less.

A 2018 study published in the British Medical Journal reported that 40 per cent of hospital patients are bothered by noise at night with levels regularly exceeding international recommendations. Another study from March 2021 showed that noise levels as high as 88dB have been measured in intensive care units.

UK team sounds off with metamaterial bricks

World’s first sound projector targets willing individuals

Metasonixx, the company behind the Sonoblind panels, is a spin out from the Universities of Sussex and Bristol. The company, founded by Dr Gianluca Memoli, from the School of Engineering of Informatics of Sussex University, and by Prof. Bruce Drinkwater, of Bristol University, has just been awarded the Armourers & Brasiers Venture Prize, which comes with £25,000 investment.

“Our panels are much lighter than traditional solutions for noise abatement and, if required, can even let air and light through,” said Dr Memoli. “Some of the panels can be used as grilles to silence air conditioning units and extractor fans or as part of blinds, to keep the noise out while the window stays open.”

In 2017, Dr Memoli and Prof. Drinkwater reported the creation of a layer of metamaterials using 16 varieties of small 3D printed bricks that each manipulate sound in a different way. Incoming sound waves could be transformed into an acoustic field of any shape depending on how the layer of bricks is configured.

“We demonstrated that acoustic metamaterials could be composed using 16 pre-defined unit cells,” Dr Memoli told The Engineer. “One of these unit cells causes a phase delay of 180 deg….so if we were making a noise-cancelling headphone, working in a small area and at a single frequency, we would just need to use two-unit cells together: one that adds delay and the other that doesn’t.

“The point is that in 2017 our “bricks” were mon-frequency. Since then, we have learned to design better bricks, working over larger bandwidths….and discovered that some configurations cause noise-cancellation over larger areas. We patented these new ideas in 2019, but only in 2020 we realised these could be used for hospitals or indoors. On the way, we realised that making a metamaterial is a design problem…and this is why the optimisation that leads to the hospital panels also includes a bit of machine learning.”

Trials are about to start in UK hospitals in an attempt to reduce the constant noise on busy wards.  A 2020 study conducted at St. George’s hospital in London attributed unwanted noise mostly to medical equipment, such as ventilators, and their buzzing alarms.

Metasonixx is also set to work with MOVYON, the centre for research and innovation within the Autostrade per l’Italia Group. This project will use metamaterial panels externally to create quiet areas for drivers in quiet outdoor settings.