Convergence of acoustic echo cancellers for hands-free telephones operating under feedback conditions

Acoustic echo cancellers for conference circuits with hands-free telephones are capable of identifying a time-invariant room without problems, if no disturbances appear and no feedback exists over a second room. In practice, these conditions are rarely fulfilled. The conditions are given under which acoustic echo cancellers within a closed-loop conference circuit attain the same convergence behavior as in the open-loop case without additional difficulties