Character for the definition of signals for controlling the journals eco voice

摘要

Long-lasting periodic signals cannot be cancelled in a speech echo canceller and this leads to instability after a time when such signals have been received. An arrangement is therefore required to detect periodic signals, such as sine-wave signals, but also frequency combinations, which can prevent modification or increase in the coefficient set in the adaptive transversal filter of the speech echo canceller. The detection circuit according to the invention contains an auxiliary echo canceller (10), the output (16) of which is compared with the signal on the receiving path (4) and thereby with the input of the detection circuit. A delay component (42) is connected in front of the adaptive transversal filter (15), whereby the filter (15) is no longer able to cancel non-periodic signals. As a result of this, only periodic signals produce a small-value output signal (16) of the auxiliary echo canceller (10) and the comparator (25) emits a blocking signal. IMAGE