Lessons learned for implementing near-field active control systems to achieve global control of fan noise

Abstract

Work has been ongoing for a number of years to develop compact active noise control systems that can effectively achieve global attenuation of radiated fan noise associated with information technology (IT) equipment. Both axial and centrifugal fans are used in IT applications, and both types of fans have been studied. An approach has been developed that can guide the user to properly implement near-field sources and sensors to achieve significant global attenuation of the fan noise. These concepts have been investigated experimentally in numerous configurations to verify the effectiveness of the approach. Both narrowband and broadband noise components have been targeted, and limitations on the attenuation that can be achieved have been established. The sensitivity of various configurations has also been studied, and it has been found that some implementations may be able to achieve greater attenuation, but are also much more sensitive to placement errors of the sources and sensors. This paper will overview the research to date and provide an overview of lessons that have been learned for effective implementation of near-field control techniques in order to achieve global attenuation.