Patent ID: 6683960
Filing Date: 2004-01-27
Classification: G10K,H03H

Abstract:
An active noise control apparatus for updating a coefficient of a noise control filter which synthesizes a secondary noise having a same amplitude as and an opposite phase to a noise to be suppressed:the noise control filter comprising a first and a second noise control filter respectively having a first and a second arbitrary coefficient, the apparatus further comprising: a first and a second overall system filter which form an overall system filter for simulating a characteristic of an overall system leading to an error detecting microphone from a noise detecting microphone that detects a noise component required for synthesizing the secondary noise, and which has a first and a second coefficient respectively obtained for the second and the first coefficient, a differential overall system filter for outputting a response difference of the first and the second overall system filter, and an estimating noise transfer system filter, having a variable coefficient, connected to the differential overall system filter in cascade, a white noise generated by a white noise generation circuit being applied to respective cascade combinations of the first overall system filter and the second noise control filter, and the second overall system filter and the first noise control filter, and to the differential overall system filter; the coefficient of the estimating noise transfer system filter being updated in order that a difference between the output of the differential overall system filter and a differential output between the first and the second noise control filter becomes a minimum, and the coefficient of the estimating noise transfer system filter obtained at a time when the difference becomes the minimum being provided as the coefficients of the noise control filters.