Active nonreciprocal structural control on a flexible plate

Reciprocity is an acoustic property that describes the symmetry of sound transmission between two points. However, this property is undesirable in certain applications, and this has led to significant interest in the development of nonreciprocal acoustic devices that achieve one-way sound transmission. These devices typically achieve nonreciprocal sound transmission by introducing nonlinearities or directional biasing. Previously proposed nonreciprocal acoustic devices generally have limitations; for example, they may not be fully adaptable, they can introduce signal distortions such as additional harmonics, or they can only exhibit nonreciprocal behaviour over a narrow bandwidth. To overcome these challenges, previous work has demonstrated how an wave-based active control system can be used to drive an array of acoustic sources to achieve reversible and broadband non-reciprocal behaviour. This paper aims to extend this concept to a linear wave-based active structural-acoustic control system that uses an array of structural actuators to control the individual wave components to achieve broadband nonreciprocal transmission through a flexible plate in a three-dimensional environment. The performance of the wave-based active controller has been investigated at a range of incident angles and the limits of this controller have been identified.