On the positioning of control sources in active noise control of three-dimensional interior space

Abstract

Locations of secondary sources in three-dimensional active noise control influence greatly on final control result. To find efficient secondary source sites for given primary source layout, an acoustic analysis of a three-dimensional interior space is done for low frequency ranges with low modal density. By using the boundary element method, magnitude and phase of optimum velocities of boundaries are evaluated for underdetermined system with an example of a rectangular box. Because the potential energy at mutiple field points depends on boundary velocity field, "good" sites for control sources can be determined by investigating the distribution of resultant velocity vectors. Results show a general tendency that the dipole positioning is most effective and the source should be placed at antinodes of related modes for maximum noise reduction, and this agrees with previous ones. With this method, positions of control sources for maximum noise attenuation can be determined for a variety of primary source configurations and for irregular boundary shapes.