Importance

Loading Importance Indicators...

Abstract

A supplemental echo suppressor controls the attenuators in a transmit path and receive path to selectively set the attenuations based on the signal received from the far-end and the signal transmitted from the near-end. The attenuation levels are set to allow full-duplex communication. If both ends supply speech signals simultaneously, the attenuation is reduced, increasing the clarity of signals at both ends. Attenuation levels are also set when both ends are idle. If, however, the far-end user is talking and the near-end user is silent, and the echo at the near-end is low, then the attenuation is set high. Signal parameters are generated and monitored to control echo suppression. Suppression attenuation decisions are determined on the basis of normalized power estimates that are normalized to a background power estimate that is indicative of background noise. The power and noise parameters are used to determine engagement and disengagement of the suppressors. A slow noise signal is used as a control parameter for controlling suppression. The slow noise is a secondary, lower variance background power estimate that is derived from a background power estimate. The background power estimate, in turn, is derived from a power estimate of an input signal. An Echo Return-Loss Enhancement (ERLE) expectation value is used as a control parameter to discriminate between speech signals and echo signals which, in turn, is used to make suppression gain decisions.

Loading the Abstract Image...

First Claim