An acoustic metamaterial is a material in which its acoustic properties are derived not from the characteristics of its constituent atoms, but from the shape and geometry - the way that it is built, not from what it is built. Such metamaterials can be constructed in such a way as to create material properties that are impossible in traditional materials, such as negative density and negative bulk modulus - properties counterintuitive to the way in which we expect materials to behave. Acoustic propagation in these materials is unusual, and metamaterials can be used to cloak objects from sound, to show extremely efficient noise suppression, and otherwise manipulate sound in strange ways. One issue to tackle, to make these materials more relevant to real-world applications, is one of scale. Miniaturisation of these structures is desirable to improve efficacy and efficiency, and make metamaterials perhaps wearable, i.e. such that the materials are on the scale of human endeavours. The problems are that typically acoustic systems work at ever higher frequencies as they are miniaturised, moving away from audio frequencies, and also that creating small structures to enable wearable materials in, for example, headphones, is challenging and expensive. Advanced manufacturing methods are progressing such that it is possible now to build complex geometrical objects using 3D-printing methods with features in the microscale, not least due to recent developments in our laboratories and others worldwide. This opens up the possibility of rapidly prototyping small acoustic systems - miniature musical instruments - that can be stacked together to create acoustic metamaterials, while still working at audio frequencies. In this project, we seek to establish new acoustic systems built with microscale features that operate at audio frequencies pulling together advances in 3D printing and acoustic system design to create materials that have exceptional acoustic performance while being lightweight and small scale. The landscape of potential material design, enabled by our work on novel polymers and 3d printing technology, is such that we can aim to develop systems for personal audio that could constitute the science of audio of acoustic systems for the next generation of technologies in wearable consumer products.

This Digital Economy (DE) Network Plus will deliver a vibrant community that will position the UK as the internationally leading research hub for Digitally Enhanced Advanced Services. Rather than focus on the product or service that is delivered DEAS focuses on how the product or service is used. This is a major change in how firms earn money and is being enabled by transformative digital technologies that allows for example, payment per use or availability or outcome. The impact of these changes is in firm productivity. The traditional focus of productivity (outputs/inputs) is on internal efficiency. However, digital technologies can also transform the value of the output (payment for use, availability or outcome). Haldane (Chief Economist of the Bank of England) in his recent report on productivity puzzle (essentially stagnant growth since the financial crash) argues that despite the advent of the digital age and their adoption by some leading companies there is a very long tail of poorly productive firms across all sectors. He calls for the development of, for example, online tools that will speed the process of technological diffusion to the long tail. The development of the underpinning digital technologies for the purposes of developing DEAS is the key research challenge adopted by this Network+.