Abstract: An echo cancellation device for reducing a magnitude of an echo occurring in a voice signal propagating in a channel of a communication system. The echo cancellation device is capable to selectively acquire an active operative mode and an inactive operative mode in response to a condition indicative of a level of echo present in the voice signal. In the active operative mode the echo cancellation device performs echo cancellation on the voice signal. In the inactive operative mode the echo cancellation device allows the voice signal to propagate without performing any echo cancellation.

Abstract: In methods and apparatus for processing a speech signals comprising a plurality of successive signal intervals, each signal interval containing no speech sounds is classified as a noise interval, and LPC coefficients are calculated for each noise interval based on the samples of that noise interval and on the samples of a plurality of preceding signal intervals. When noise intervals encoded using LPC coefficients calculated as described above are reconstructed, the subjectively annoying "swishing" or "waterfall" effects encountered in conventional LPC speech processing systems are reduced or eliminated.