Application of MVDR beamforming to reject turbulence noise in a duct

In active noise control (ANC) on air duct/fan systems it is desirable to achieve noise cancellation using the shortest possible duct length. A barrier to this goal is the presence of air turbulence at the duct input due to the fan driving the system. Turbulent pressure fluctuations contaminate measurement of the acoustic noise in the duct, resulting in degraded noise cancellation performance. We investigate the use of adaptive array processing techniques to suppress the effects of turbulence. Based upon the spatial correlation and temporal spectral characteristics of turbulence, we propose a hybrid generalized sidelobe canceller (GSC) which is constrained to adapt only in the frequency range where both acoustic noise and turbulent noise contribute correlated components to the multivariate input covariance. The effectiveness of this method is demonstrated using actual experimental data