NOISE REDUCTION APPARATUS

摘要

A noise reduction apparatus (10) for an enclosure (12) is disclosed, comprising error sensors (22a, 22b) to generate an error signal (46), reference sensors (22a, 22b, 22c), a controller (24) having a reference signal conditioning circuit (24c) to produce a reference signal (32) from the reference sensors (22a, 22b, 22c), the controller (24) being responsive to the reference signal (32) to produce a control signal (44); transducers (26a, 26b) responsive to the control signal (44) to reduce noise in the enclosure (12) near the error sensors (22a, 22b). The controller (12) comprises a first controller (38) responsive to the reference signal (32) to produce the control signal (44) for the transducers (26a, 26b), a plant model (48) responsive to the reference signal (32) to produce a signal input to a second controller (50), signal generating circuit (52) for producing a further error signal (56) from the output of the second controller (50), the output of the first controller (38) and the error signal (46), and an adaptive LMS system (40) responsive to the further error signal (56) to adjust the parameters of the first and second controllers (38, 50) simultaneously. The controller (24) allows fast convergence rates compared with filtered-X controllers. A shaping filter (42) is provided to allow a user to adjust the attenuation characteristics of the controller (42) to suit his or her preference.