A review of the effect of reflective surfaces on power output of sound sources and on actively created quiet zones

© S. Hirzel Verlag EAA. It is known that active noise control systems behave differently in free space and half space. However analysis of active noise control applications has generally neglected the presence of a reflective surface. The objective of this paper is to review the effect of a reflective plane on an active noise control system. This effect is subject to the characteristics and configurations of the noise sources, control sources, sensors and the reflective plane itself. These configurations include the directivity pattern of sources, distance of sources from the plane, orientation angle of sources to the plane, number of control sources, and frequency of the primary noise. It is shown how the power output and the size of the quiet zone depend on these factors. The research papers dealing with reflective planes are reviewed and discussed. Recent trends of active noise control systems in free field conditions with respect to the control performance are also highlighted. Some applications of active noise control technology are given and recent progress in the field outlined. Finally, research directions in this particular area are suggested.