ASA 124th Meeting New Orleans 1992 October

4aSA13. The active control of point acoustic sources in a half-space.

Kenneth A. Cunefare

Steve Shepard

George W. Woodruff School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332-0405

Analytical analyses of active noise control applications generally neglect the presence of nearby reflective surfaces, such as a ground plane. This paper examines the impact of the presence of a nearby reflective plane on the active control of sound radiated by a number of point sources. It is shown that when the sources to be controlled are within one wavelength of the reflective plane, be it rigid or pressure release, that the plane can significantly impact the control versus control under free-field conditions and with the same source separations. The orientation of the noise sources and the control sources with respect to each other and to the plane also significantly influences the control. For sources more than one wavelength away from the reflective plane, the use of the simpler free-space analysis yields acceptable results as compared to using the more complex half-space analysis.