| 摘要 |
<p>In communication networks with transmission devices using analog circuitry, because of unadapted 4-wire/2-wire junctions, some of the speech of a local speaker comes back to the local speaker as line echo. This line echo is neutralized by echo compensators. However, updating of the filter coefficients of the echo compensators cannot be allowed to occur unless line echoes are received: when speech of the far-end speaker is received, recalculation of the filter coefficients must be precluded. Various possibilities for detecting the speech of a local speaker are well known. According to the invention, detection of the speech of a far-end speaker is fed back to an attenuation measurement of the transmission path, received speech simulates a reduction in attenuation. From the difference between the longtime average (Aa(k+l)) and the short-time average (A(k+1)) of the attenuation, it is learned very quickly, by comparison with a threshold (THRe), whether speech is present or not. The method is also applicable in order to discontinue automatic voice output on the local end by means of duplex voice communication.</p> |
