A silencer is to be used in combination with a range hood system to suppress noise made by a fan. In a silencing circuit, a disturbance detector detects mixing of disturbance sound to a correction signal and an error signal. When the disturbance detector detects the mixing of the disturbance sound, an updating stopper causes a coefficient updater to stop a processing of updating a filter coefficient of a silencer filter, relating to, as an object, at least a frequency band other than a frequency band of the noise.