Förfarande och anordning för konstruktion av digitala filter

摘要

A digital filter design apparatus for noise suppression by spectral subtraction includes a first spectrum estimator for determining a high frequency resolution noisy speech power spectral density estimate from a noisy speech signal block. A second spectrum estimator determines a high frequency resolution background noise power spectral density estimate from a background noise signal block. Averaging units form a piece-wise constant noisy speech power spectral density estimate and a piece-wise constant background noise power spectral density estimate. These averaging units are controlled by devices for adapting the length of individual segments to the shape of the high frequency-resolution noisy speech power spectral density estimate and for using the same segmentation in both piecewise constant estimates. A piece-wise constant digital filter transfer function is determined using spectral subtraction-based on the piece-wise constant noisy speech power spectral density estimate and the piece-wise constant background noise power spectral density estimate.