Global active control of axial cooling fan noise: An overview of past and present research

During the past eight years, researchers at Brigham Young University have been engaged in a pragmatic effort to actively reduce the noise radiation from small axial cooling fan noise. The first of a series of studies on the subject demonstrated that a feedforward, multichannel controller with near-field error sensors was successful in globally reducing four harmonics of the blade passage frequency. Additional studies have revealed optimal locations for both error sensors and control sources and have further reduced the spatial footprint of the system actuators. Other issues, such as the impact of a reverberant enclosure on control and the use of feedback control to reduce the broadband noise have been looked at, but are the subject of ongoing investigations. a Email address: [email protected] b Email address: [email protected]