Active noise cancellation system having an adaptive filter and a correction filter

摘要

In an active noise cancellation system having an adaptive filter (16b) that outputs a control signal, first and second speakers (20f, 20r) that emit a canceling signal generated based on the control signal, a microphone (22) that detects an error signal (e), a correction filter (16c) that corrects the base signal by a correction value to generate a reference signal (r) and an adaptive algorithm (16d) that successively updates the adaptive filter coefficient based on the error signal and reference signal such that the error signal is minimized, the correction value of the correction filter is set to a sum obtained by adding the transfer characteristic from the first speaker to the microphone, and a product obtained by multiplying the transfer characteristic from the second speaker to the microphone by the prescribed value, thereby enabling to reduce the number of microphones and avoid the increase in parts, the amount of work to provide complicated wiring to the microphones, and the computational load involved in updating the adaptive filter coefficient, while enabling to maintain an area in which noise can be reduced to the same level as that obtained before reducing the number of microphones.