Active control of scattered acoustic fields: Cancellation, reproduction and cloaking

The active control of sound fields has been widely applied in both active noise control and sound field reproduction, however, relatively few studies have focused on active acoustic cloaking. In order to build upon the knowledge and understanding in the areas of active noise control and sound field reproduction, this paper investigates the corresponding physical limitations and compares them to the active cloaking problem when the three strategies are employed in the presence of an acoustic scatterer. The three sound field control strategies have been formulated within a consistent framework, and this has enabled insight into the physical control mechanisms. Two different three-dimensional scattering problems have then been simulated and used to investigate the performance limitations of the three strategies. The influence of the number and proximity of control sources to the scattering object have been investigated, and it has been shown that the requirements for active cloaking differ from those for active noise control and sound field reproduction. Specifically, it has been shown that there is a clear distinction between controlling the internal and external sound fields in the three cases.