Active control of a finite line source using multiple directional sources

Abstract

The active control of a finite line source in free space is studied using different types of secondary control sources to create a particular quiet zone. The simulations based on analytical formulation indicate that the active control improves significantly with the usage of directional secondary sources, such as axially oscillating baffled circular pistons. The comparison between directional sources of different directivity patterns shows that the directivity property has a determinant effect on the control results. A multi-part directional source, then, is introduced as the novel secondary control sources with its simplest two-part type. It consists of an inner-piston and an outer-concentric-annulus both oscillating axially with optimized amplitudes and relative phase. This novel secondary source helps to achieve excellent control results within a realistic physical size. The control performance regarding the novel sources with more outer annuluses are also studied.