ACTIVELY CREATED QUIET ZONES BY MULTIPLE CONTROL SOURCES IN FREE-SPACE

Local attenuation of sound pressure, which creates a zone of quiet, se ems to be the only option if primary and secondary sources are well se parated. Two major indexes of local control, the size of the quiet zon e and the total sound power output, are mainly determined by the arran gement of primary sources, secondary sources, and error sensors. It ha s been found that the size of the quiet zone created by the control sy stem with multiple secondary sources and error sensors is not simply t he summation of quiet zones created by each individual control source. The interactions of the control sources, which are determined by the configuration of the system, play a very important role in the system performance. In this paper, a typical control arrangement with multipl e secondary sources and multiple error sensors equally spaced in two p arallel lines is examined. Results from computer simulation and experi ments in an anechoic chamber show that there exists a range of optimal spacing for the secondary sources and error sensors. The control syst em will create the largest quiet zone and suffer the least increase of total sound pourer output in the optimal configuration. (C) 1997 Acou stical Society of America.