The UK is a world leader in the design, manufacture, and support of high-value aeronautic structures such as wings and jet engines. The UK's technology strategy is to reduce aeronautic structure weight by 35% by 2035 compared to 2019. Lighter structures are prone to complex nonlinear phenomena which cannot be identified and characterised using current ground vibration tests (GVTs). Building on recent advances in control-based continuation and nonlinear modal analysis, this project will develop a general and systematic GVT method that can overcome this issue. The method will be demonstrated on two academic benchmark structures before being tested on a full-scale aircraft structure thanks to an international collaboration with ONERA. The project will not only unlock the rigorous characterization of modal properties of nonlinear structures but will also bridge the gap currently preventing the development and validation of nonlinear models.

It is well established that long-term exposure to aircraft and wind turbine noise is responsible for many physiological and psychological effects. According to the recent studies, noise not only creates a nuisance by affecting amenity, quality of life, productivity, and learning, but it also increases the risk of hospital admissions and mortality due to strokes, coronary heart disease, and cardiovascular disease. The World Health Organization estimated in 2011 that up to 1.6 million healthy life years are lost annually in the western European countries because of exposure to high levels of noise. The noise is also acknowledged by governments as a limit to both airline fleet growth, acceptability of Urban Air Mobility, operation and expansion of wind turbines, with direct consequences to the UK economy. With regards to aerodynamic noise, aerofoil noise is perhaps one of the most important sources of noise in many applications. While aerofoils are designed to achieve maximum aerodynamic performance by operating at high angles of attack, they become inevitably more susceptible to flow separation and stall due to changing inflow conditions (gusts, wind shear, wake interaction). Separation and stall can lead to a drastic reduction in aerodynamic performance and significantly increased aerodynamic noise. In applications involving rotating blades, the near-stall operation of blades, when subjected to highly dynamic inflows, gives rise to an even more complex phenomenon, known as dynamic stall. While the very recent research into the aerodynamics of dynamic stall has shown the complexity of the problem, the understanding of dynamic stall noise generation has remained stagnant due to long-standing challenges in experimental, numerical and analytical methods. This collaborative project, which includes contributions from strong industrial and academic advisory boards, aims to develop new understanding of dynamic stall flow and noise and develop techniques to control dynamic stall noise. The team will make use of the state-of-the-art experimental rigs, dedicated to aeroacoustics of dynamic stall and GPU-accelerated high-fidelity CFD tools to generate unprecedented amount of flow and noise data for pitching aerofoils over a wide range of operating conditions (flow velocity, pitching frequency/amplitude, etc.). The data will then be used to identify flow mechanisms that contribute to the different aerofoil noise sources at high angles of attack, including aerofoil unsteady loading and flow quadrupole sources, and detailed categorisation of dynamic stall regimes. A set of new frequency- and time-domain analytical tools will also be developed for the prediction of dynamic stall noise at different dynamic stall regimes, informed by high-fidelity experimental and numerical datasets. This project will bring about a step change in our understanding of noise from pitching aerofoils over a wide range of operations and pave the way to more accurate noise predictions and development of potential noise mitigation strategies.

Earth is a Noisy Planet. Human activity means that from megacities to oceans, most places are infected with noise and tranquility is disappearing. This was starkly illustrated during the Covid-19 pandemic lockdowns when transport and industry largely stopped, and we glimpsed what a better-sounding future might be. Noise is a health problem for one in five European citizens. At high levels it causes hearing loss. At moderate levels it creates chronic stress, annoyance, sleep disturbance and heart disease. Noise makes it harder to communicate, harming learning in schools and increasing withdrawal of older people from social situations. The 2023 House of Lord's Science and Technology Committee report called noise a "neglected pollutant" and recommended more research to reduce harms. Noise also increases mortality in marine and terrestrial wildlife. The CDT will go beyond noise control to research how to engineer positive sounds. From using sound to improve the accessibility of products, through to enhancing cultural events that boost well-being, there are many ways of creating a better aural future. The CDT focuses on the user need of businesses, society and government to create a more Sustainable Sound Future. In EPSRC's Tomorrow's Engineering Research Challenges, the sound of drones and environmental noise are highlighted as needing innovative solutions. This CDT will not only cover this challenge, but will also contribute to seven out of eight Tomorrow's Engineering Research Challenges, because noise and vibration cuts across many sectors such as transport, energy, environment, construction and manufacturing. Through the CDT, we will address recruitment issues faced by the UK's £4.6 billion acoustics industry. Our partners tell us they struggle to find doctoral-level graduates in acoustics. Cohort training will empower our CDT graduates with an unprecedented depth and breadth of knowledge. This is needed because of the complexity of the challenge, from re-engineering machines, systems and buildings, through to understanding how sound affects the health and well-being of humans and other animals. Current PhD training in acoustics is too piecemeal to tackle a problem that cuts across sectors, regulators and society. The CDT will create a unique cohort of future research leaders and innovators, with the ability to create a step-change in how sound is tackled working across disciplines. This CDT brings together four powerhouses in acoustics: the Universities of Salford, Bristol, Sheffield and Southampton; along with industrial partners, regulatory bodies, public and third sector. This provides CDT students with access to an extraordinary range of laboratories and breadth of expertise for their training. This includes domain and application knowledge across many disciplines; state-of-the-art simulation, measurement and auralisation capabilities; datasets and case studies, and routes to impact. The CDT builds on EPSRC's UK Acoustics Network that has over 1,700 members including 500+ early career researchers. Challenging interdisciplinary research projects and cohort-based training will develop the much-needed postgraduates. A mixture of week-long residentials, group project and online activities are planned. These will develop technical skills for acoustics (simulation, measurement, machine learning, psychoacoustics, etc. and key skills for research (project planning, entrepreneurship, public engagement, policy influencing, responsible innovation, etc.). Partner placements will play an important role in ensuring the cohort learns about context and how to create impact. The learning outcomes of the training have been co-created between academics and partners, to ensure CDT graduates have the skills, knowledge and understanding to create a more sustainable sound future for all.