ACTIVE NOISE REDUCING DEVICE

摘要

An active noise reducing device canceling vibration and noise based on the output of an adaptive notch filter (4), wherein when the amount of a variation between the present value and the past value within a specified time of engine pulses inputted into the adaptive notch filter (4) is equal to or higher than a specified value, an engine pulse monitoring means (25) cuts off a switch (26) to stop the output of the adaptive notch filter (4). Before the update speed of a coefficient of adaptive notch filter cannot follow up an engine speed when the engine speed is suddenly changed and the adaptive notch filter (4) is diverged, the output of the adaptive notch filter (4) is stopped to prevent abnormal noise from occurring. Thus, even if the engine pulses are suddenly changed, the abnormal noise outputted from the adaptive notch filter (4) does not reach a user.