Echo return loss required for acoustic echo canceller based on subjective assessment

In wideband audio teleconference systems, speech quality may be degradated due to acoustic echo in the conference room. Echo control devices such as an echo canceller can be used to improve the speech quality. This paper describes echo return loss required for acoustic echo cancellers based on subjective assessment. In particular for talker echo, subjective evaluation was pursued using a simulated wideband audio teleconference system constructed in our laboratory. Test conditions were combinations of transmission delay and insertion loss against echo path. The thresholds of detectable and/or objectionable echoes based on subjective evaluation are clarified.