The acoustic environment can have as much impact on humans as temperature and light. In cities, unwanted noise often penetrates personal spaces, and noise on loud trains, buses and tubes can cause significant discomfort to travellers. Noise pollution in general is becoming a major problem in Europe: the number of people exposed to levels of environmental noise above noise indicator levels set by the EU Environmental Noise Directive exceeded 53 million in 2018. The ability to reduce sound transmission from one environment to another is therefore crucial. Current soundproofing technologies are based on specific material properties or microstructures, such as dampening foam. Usually they must be made from high-density materials and can be very expensive. Acoustic metamaterials are materials designed to control, direct and manipulate sound waves, and are a promising candidate for use in sound control technologies. Rather than depending on specific materials, their success comes down to the specific characteristics of structure shape. “Metamaterials include all those materials that, thanks to an appropriate design and functionalisation of the topology, achieve specific physical characteristics and performances greater than those of raw materials available in nature. These properties do not depend, therefore, on the microscopic and molecular nature of the constituent materials but only on the final geometry and topology,” explains Giovanni Capellari, co-founder of Phononic Vibes. The EU-funded PHOMETAPAN project, hosted by Phononic Vibes, developed a new technology based on acoustic metamaterials. The system absorbs and isolates unwanted sound vibrations to control the level of sound which passes through. At just 5 cm wide, PHOMETAPAN’s innovative new panels can reduce noise by up to 2 orders of magnitude compared to competitor soundproofing products.
The technology is based on a subset of metamaterials called phononic metapanels. The panels rely on the physics of mechanical structures known as phononic crystals, artificial structures based on repetition of a unit cell, designed to maximise sound insulation. The new structure can isolate and interrupt noise, and is made of recycled plastics, allowing the system to be more sustainable than the existing soundproofing panels. “The PHOMETAPAN project aims at industrialising the complicated topology of the unitary cell and assessing the potential for commercial exploitation of the system,” adds Capellari, PHOMETAPAN project coordinator. The team has successfully tested the products within a laboratory setting. Some products have already been designed to work in industrial applications, yet the technology could easily be used within homes, reducing unwanted sound from washing machines, dishwashers and other noisy appliances. Construction companies and real estate operators could therefore also benefit.
Establishing Europe as a leader in sound control
The PHOMETAPAN project aims to put Europe at the forefront of sound technology, promoting the use of metamaterials across a range of different sectors, markets and industries. A coach, appointed during the project, helped the team increase their knowledge about market analysis, product development and business development, while the EU grant money helped them to test out the technical and commercial feasibility of the metapanel. “Without the support of EU initiatives, new businesses based on academic research such as this one would be impossible,” says Capellari.
PHOMETAPAN, acoustic, noise, sound, design, metamaterials, phononic, crystals, structure