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 for producing afirst difference signal as a noise cancelled signal by subtracting a firstpseudosignal from an input signal having a main signal and a first noise signalsuperposedon the main signal and a first adaptive filter for processing a second noisesignalcorrelated with the first noise signal into the first pseudo signal inaccordance withfilter coefficients thereof, a second subtractor subtracts a second pseudosignalfrom the first pseudo signal to produce a second difference signal. A secondadaptive filter processes the second noise signal into the second pseudosignal inaccordance with filter coefficients thereof. First and second power averagingcircuits produce first and second power averages of the second differencesignaland the first pseudo signal, respectively. A step size calculating circuitcalculates,from the first and the second power averages, a step size used for renewingthefilter coefficients of each adaptive filter in deciding a rate of convergenceof eachadaptive filter. The first adaptive filter renews the filter coefficientsthereof intorenewed filter coefficients in accordance with the second noise signal, thefirstdifference signal, and the step size. The second adaptive filter renews thefiltercoefficients thereof into renewed filter coefficients in accordance with thesecondnoise signal, the second difference signal, and the step size.