ℋ∞ active noise control of fan noise in an acoustic duct

In this paper, the problem of reducing fan related noise in an acoustic duct is considered. By installing magnetic bearings on the noise producing machinery, it is possible to collocate 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. The controller design is based on a state space model identified from an infinite dimensional physical model. Simulation results demonstrate the global nature of this novel active noise control approach