Abstract:
Adaptive echo cancelers have been used successfully for over a decade to combat echoes that arise on a telephone network due to mismatches in impedance at various points in the circuit. Echoes arise in teleconferencing too, due to coupling between the loudspeaker and microphone in each room. This problem is similar to the network echo problem, although the impulse responses are longer and can change more rapidly. When echoes arise in a stereophonic system, however, the problem changes character due to an inherent nonuniqueness in estimating the echo paths. In this talk we will review the current status of the problem of stereo echo cancellation. After a brief introduction to the general problem of echo control, the nonuniqueness mentioned above will be discussed and then several approaches will be described to get around this nonuniqueness. At present echo path responses can be matched with an error of less than -20 dB, without any loss of the stereophonic effect.