A variable length lattice filter for adaptive noise cancellation

The variable length filter for adaptive noise cancellation (ANC) of non-stationary signals is introduced. It is shown that this filter can always act positively even when the cross-correlation between the input channels is close to zero. Results of engine noise cancellation in the ear passengers compartment using a variable length SG lattice filter are given. For these non-stationary signals, the variable length filter yields a better noise reduction than the conventional LMS (widrow) and lattice filters.