Robust global control of fan noise in an acoustic duct using magnetic bearings

An approach is presented to reduce fan related noise in an acoustic duct. By installing magnetic bearings on the noise producing machinery, it is possible to colocate the anti-noise source with the disturbance noise source. This approach allows for global noise reduction through out the duct system. Using H_∞ control theory, an active noise controller is designed that attains broadband as well as tonal noise reduction at all points along the duct. H_∞ control designs are particularly robust to uncertainties in the plant model. Finally, simulation results demonstrate the global nature of this novel active noise control approach