Study of causality constraint on feedforward active noise controlsystems

摘要

Feedforward active noise control (ANC) systems function asnadaptive system identification, thus able to control both broadband andnnarrowband noises. When the acoustic/electric delays in the noisencancelling subsystem exceed the acoustic delay of the primary path, thencausality constraint will be violated. We present a performance analysisnof the feedforward ANC system for ducts (one-dimensional acoustic field)nunder the noncausal condition. The bandwidth of the noise controllablenby the ANC system decreases as the degree of noncausality increases.nNoise with narrower bandwidth can be more effectively cancelled out bynthe ANC system with a given degree of noncausality. Analysis also showsnthat the convergence speed for the adaptive weight vector is independentnof the degree of noncausality