Audible sound is an inevitable physical phenomenon which can be “the best or the worst of things”. In its best form, it is essential for human communication and entertainment. In its worst form, it appears as a social and health threat through noise in urban and domestic environments, arising from sources such as vehicles, ventilation systems, construction sites or aircraft engines. Both European and international organisations promote noise as a major health issue of modern society and insist on regulating noiseits regulation. Although modern noise reduction solutions exist, and even using artificial periodic composites and profiting from the evolution of modern fabrication techniques, an important problem regarding sound absorption remains unresolved and unexplored.
High amplitude nonlinear waves cannot be absorbed using the existing conventional techniques and devices. These high amplitude waves pose an even larger problem than noise,; when they appear in applications such as power plants or gas transport systems they might cause significant environmental, reliability, and safety problems stemming from vibration and structural fatigue.
InFrom an original perspective, the NASA project, will utilise recent results from non-Hermitian physics to tame and absorb high amplitude, nonlinear sound waves. The project strives not only to uncover the most prominent sources of nonlinearity in acoustic isolation solutions, but in an unconventional manner to use active nonreciprocal devices and modern concepts such as topological phenomena to efficiently absorb nonlinear acoustic waves. Nonlinearity, known to lead intoto complex physics, chaos, and randomness, and in conjunction with non-Hermiticity, raises fundamental questions, and their synergy may revolutionize our ability to control waves. Within NASA, I aim to develop novel design principles and tools which will foster the development of efficient, customisable, and reliable technologies for noise reduction, especially in heavy industry and aviation.