Abstract: A multi-actuator system for active sound and vibration cancellation utilizes an LMS type algorithm having an adaptive filter. However, the error signal rather than the input is filtered through an adjoint filter of the error channel to drive an adaptive filter which in turn drives, for example, a loudspeaker to provide destructive interference for noise cancellation. The adjoint filter is realized by converting a standard filter's flow direction, such as a finite impulse response filter, swapping branching points with summing junctions and unit delays with unit advances. For multiple-input-output systems, computational complexity is significantly reduced.