Echo eliminator

Abstract

A echo elimination device comprises adaptive filter, used to simulate echo signal in work window; delay estimator with long-term energy, used to estimate time delay of echo path and transmit work signal of adaptive filter in effective coverage to adaptive filter according to time delay simultaneous; echo elimination device is used to echo signal; nonlinear processor decides whether to set zero or pass entirely for output signal of echo elimination device. It can decrease amount of calculation of adaptive filter by the method. Compared with delay T1 by traditional delay estimation method, the invention can decide more accurately the delay T2 of echo path, more approach to real delay T3, and then avoid utility imperfection of effective zone of filter parameter, solve echo elimination imperfection by traditional method and the divergence problem in real system.

Description

technical field [0001] The present invention relates to an echo canceller using a novel device and algorithm for estimating echo paths, in particular to a device and method for estimating echo delays using long-term energy, which is used to eliminate the Leakage speech signal produced by mixing part of the receiving speech signal into the sending speech signal. Background technique [0002] In the public switched telephone network, the echo phenomenon is caused by the impedance mismatch of the four-wire two-wire converter called a hybrid circuit. The combination of this echo and network delay is responsible for the degradation of voice quality. In order to eliminate this echo phenomenon, an echo canceller is generally equipped to prevent the degradation of voice quality. [0003] Existing echo cancellers use an adaptive filter known as a normalized least mean square (NLMS) to estimate and remove echoes returning from the hybrid circuit. However, with the development of vo...

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Problems solved by technology

[0004] The downside of conventional echo cancellation is that the filter requires a lot of computation

However, according to the echo path in the ITU-T standard, the echo path delay time is not equal to the position of the maximum value of the absolute value of the filter coefficient, but is about 5 milliseconds before the maximum value. If the position of the maximum value of the absolute value is The delay time will make the estimated echo path inaccurate, so that the echo cancellation in the actual system is not complete, and even cause the echo canceller to diverge

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