In conventional dereverberation schemes, it had been difficult to determine with precision a linear reverberation removal filter for removing non-fluctuating reverberation components when fluctuating reverberation components are present. The present invention provides an integrated algorithm for a dereverberation scheme using a linear filter and a dereverberation scheme using a nonlinear filter, and the algorithm has a function for measuring the amount of fluctuation in a transfer function per time for the nonlinear filter of the subsequent stage and controls the intensity of the nonlinear filter per time on the basis of that function. This allows for a configuration such that intensive nonlinear processing is applied only when the fluctuation of the transfer function is large; therefore, distortion in the speech component can be kept to a minimum. Further, the amount of fluctuation in the transfer function per time according to the abovementioned function is fed back to the estimation of the linear filter of the preceding stage, and the weighting for linear filter estimation values in the time periods where the transfer function fluctuates is lowered, thereby making it possible to mitigate the influence of a decrease in the precision of transfer function estimation.
展开▼
