Abstract: A digital speech encoder is constructed to include a short term analyzer for forming a set of prediction parameters a(i), corresponding to an input speech signal, and an encoder for producing an excitation signal. The encoder includes a plurality of serially coupled coding blocks, wherein each coding block includes an analysis filter, a sample selection block, and a synthesizer filter. The analysis filter outputs speech signal sample values to the sample selection block, which selects and outputs K.sub.i sample values representing a selected partial excitation signal. The synthesis filter synthesizes a speech signal corresponding to the selected partial excitation signal output by the selection block and outputs a partial excitation synthesis result to an output of the coding block. At the output of each coding block is a subtractor arranged for subtracting a partial excitation synthesis result that is output from the coding block from the speech signal to obtain a difference signal.

Abstract: The invention relates to a noise attenuation system for voice signals. The invention is based on noise signal measurement during the tonal periods of the voice. The line spectrum structure of the spectrum of the tonal sounds is utilized in the noise measurement. In this way it is possible to measure the noise of different frequency bands with the aid of narrow-band filters.