Active control of a highly directional primary source by compact novel secondary sources

Abstract

The active noise control in free space for a global attenuation is always very challenging, especially for extended and complex radiators. This work focuses on a finite simple line source possessing strong directivity of multi-lobe radiation pattern as the primary source, which is frequently encountered in traffic noise control problems modelling a busy road or the train noise. Conventional secondary sources of compact size radiate the sound wave omnidirectionally, resulting in tangible pressure level increase in off-axis areas. This paper introduces a novel constructed control source, which has reasonably directional sound radiation capability even with a very compact size in low-frequency. Comparing to common directive sources, such as axially oscillating baffled pistons, the novel sources can significantly improve the active control result in a global way.