Filtered-error feedback broadband noise control in a crew rest compartment

Abstract

Active systems for noise cancellation are typically used to reduce low frequency noise (below 500 Hz). In this study a method to reduce the delay in the control loop of feedback noise control systems is discussed. There are certain applications in which we may choose to control a specific frequency range, hence a selection of the control-band must be performed. This selection is commonly done with analog filters introducing delay in the signal path. However, in feedback systems the reference signal is calculated from the error signal which makes their performance more sensitive to these delays. In this contribution the filtered-error feedback filtered-reference LMS algorithm (FE-FBFxLMS) is analyzed. Consequently, control-band selection is performed in an auxiliary loop removing the additional delay required in the signal path. This method of band selection also allows a reduction of the delay due to the anti-aliasing filters by using faster low-order filters in terms of group delay. With this delay reduction, higher noise attenuation is expected at the cost of a slower convergence rate. This method is applied to control broadband noise in a single channel feedback system in simulation and experiment. © 2013 Acoustical Society of America.