Noise cancelling device capable of achieving a reduced convergence time and a reduced residual error after convergence

摘要

In a noise cancelling device including a first subtractor (5) for producing a first difference signal as a noise cancelled signal by subtracting a first pseudo signal from an input signal having a main signal and a first noise signal superposed on the main signal and a first adaptive filter (4) for processing a second noise signal correlated with the first noise signal into the first pseudo signal in accordance with filter coefficients thereof, a second subtractor (7) subtracts a second pseudo signal from the first pseudo signal to produce a second difference signal. A second adaptive filter (6) processes the second noise signal into the second pseudo signal in accordance with filter coefficients thereof. First and second power averaging circuits (8 and 9) produce first and second averages (P1 and P2) of power of the second difference signal and the first pseudo signal, respectively. A step size calculating circuit (10) calculates, from the first and the second averages, a step size for use in renewal of the filter coefficients of each adaptive filter in deciding a rate of convergence of each adaptive filter at a time. The first adaptive filter renews the filter coefficients thereof into renewed filter coefficients in accordance with the second noise signal, the first difference signal, and the step size. The second adaptive filter renews the filter coefficients thereof into renewed filter coefficients in accordance with the second noise signal, the second difference signal, and the step size. <IMAGE>