Abstract
Acoustic cloaking has received significant interest due to the appealing ability to render an object acoustically invisible. In a similar concept to acoustic cloaking, acoustic illusions provide the capability to misrepresent the acoustic field of an object. Combining acoustic cloaking and illusions with numerical discretization methods allow objects of greater complexity to be considered. This work presents active acoustic cloaking and illusions of three-dimensional rigid objects. The boundary element method is utilized to efficiently predict the exterior acoustic domain. A multi-input/multi-output control system comprising monopole control sources, error sensors, and a controller based on a feedforward linear-quadratic regulator algorithm is employed. Active acoustic cloaking of a simple object corresponding to a sphere is demonstrated for both non-decaying and decaying incident fields. For the same control configuration but minimizing a cost function based on different error signals, acoustic illusions are generated to mimic the presence of a sphere within a free field. Illusional fields are also generated for a cube and a bird to misrepresent their size or orientation.
Highlights
Manipulation of electromagnetic and acoustic waves has significantly advanced in the last decade, giving rise to the generation of acoustic cloaks and illusions
Where psc;e represents the scattered pressure due to an incident acoustic field at each error sensor as given by Eq (12), Z is an L Â M matrix of the transfer functions associated with the acoustic pressures generated by M control sources at L error sensors, and qcloak is a vector of the complex control source strengths to be optimized
Where pillusion;e represents the scattered pressure associated with the illusion object at each error sensor, and qillusion;1 is a vector of the control source strengths to actively generate the acoustic illusion
Summary
Manipulation of electromagnetic and acoustic waves has significantly advanced in the last decade, giving rise to the generation of acoustic cloaks and illusions. Similar passive methods have been employed to generate illusions that misrepresent the acoustic field of an object.. The aforementioned studies on acoustic cloaking and illusions were applied to objects of simple geometry, namely, cylinders and spheres. FEM has been used in conjunction with conventional active noise control to cloak a three-dimensional (3D) rigid sphere.. In contrast to the numerous studies to passively design cloaks using discretization methods, only one numerical study that utilizes the BEM has been integrated with an active control method, in which a dielectric sphere was optically cloaked using discrete monopole and dipole control sources.. An approach combining active noise control and the BEM is proposed to manipulate the acoustic fields associated with 3D rigid objects of simple and complex geometry.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
