User manual POLYCOM EF1210

[. . . ] ECHOFREETM EF1210 MULTI-CHANNEL ACOUSTIC ECHO AND NOISE CANCELLER USER MANUAL Copyright 1999 ASPI Digital. Printed in the United States of America. Because of technical progress, specifications are subject to change without notice. EchoFree is a trademark and ASPI is a registered trademark of ASPI Digital. ASPI Digital - The Sound of DSP 1720 Peachtree Street NW, Suite 220 Atlanta, GA 30309-2439 (404) 892-3200 www. echofree. com Technical Support: (404) 892-3200 help@aspi. com EF1210UM-0100-99 EF1210 USER MANUAL Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Product Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] To avoid problems, ensure that the Reference input signal (as reflected on the REMOTE SIGNAL LEVEL METER) is not too low, and the microphone input signal (as reflected on the INPUT SIGNAL LEVEL METER) is not too high. Run the built-in EF1210 Acoustic Gain test to verify that you do not have acoustic gain problems (See "Check Acoustic Gain" on page 31. ). 1. In-Conference Quick Check If you experience residual echo problems during a conference, you can quickly check that the reference and microphone levels are calibrated and not causing acoustic gain problems by observing the signal level meters as follows. While the remote end is speaking and everyone on the local end is quiet, observe the activity on the REMOTE SIGNAL LEVEL METER. Remote speech should illuminate the first yellow (0 dB) LED regularly, and the second (+3 dB) LED occasionally. Step through the microphone input channels by repeatedly pressing the INPUT SELECT front panel button while the remote end is speaking (the local end must be silent during this check), and observe the activity on the INPUT SIGNAL LEVEL METER for each microphone channel in response to the remote talker. If any microphone channel exhibits greater signal level activity than that shown on the REMOTE SIGNAL LEVEL ASPI Digital - The Sound of DSP Technical Support: 404. 892. 3200 45 EF1210 USER MANUAL METER, this indicates a possible problem with the acoustic gain on that microphone channel. If this excessive coupling activity level is evident on only one microphone input channel, that microphone channel should either be redirected to reduce coupling to loudspeaker audio, or recalibrated as it will need to be turned down. If the excessive coupling activity is observed on all (or most) microphone channels, then this indicates either that the room audio is too loud or the reference signal may need to be recalibrated (this will be indicated by observing low activity levels on the REMOTE SIGNAL LEVEL METER). Note. Before you readjust the Remote input levels, check to make sure you are looking at the correct remote input level (AEC A or AEC B) on the REMOTE LEVEL INDICATOR. Check to make sure that the microphone that you are looking at is in the zone that you think it is in and that you are looking at the correct channel on the INPUT LEVEL INDICATOR. Excessive Microphone Amplification For the EF1210 to adapt effectively, saturation (overload or clipping) must not occur at the A-D converter supplying the microphone input. Saturation introduces nonlinear signal distortions into what the AEC expects is a linearly echoed version of the remote speech. Nonlinear distortion causes a degradation or divergence of the AEC's internal model of the room acoustics. In this situation, the EF1210 cannot effectively cancel room echoes and a substantial amount of echo may be heard by the remote party. Excessive microphone amplification also increases acoustic gain (See "Acoustic Gain Failure" on page 45. ). You can check for excessive microphone amplification by observing the front panel INPUT LEVEL INDICATOR during a normal conference. The first yellow LED should illuminate frequently. If the second yellow LED is illuminated constantly during normal speech or if the red LED illuminates or even flickers, reduce the microphone input level. Note. Before you readjust the microphone input levels, check to make sure you are looking at the correct channel on the INPUT LEVEL INDICATOR. Check also to make sure that you are looking at the correct corresponding reference input level on the REMOTE LEVEL INDICATOR. If you adjust the MIC/LINE INPUT level, you will affect the acoustic gain. Check to make sure that the acoustic gain limit is not exceeded. See "Check Acoustic Gain" on page 31. Note. Insufficient Microphone Amplification Grossly insufficient microphone gain degrades EF1210 performance and weakens the out-bound speech power level. This has the effect of reducing the signal-to-noise ratio of the microphone signal, which is analogous to raising the background noise level in the room. [. . . ] This will take you to the Phone Book page of EFPanel for the EF200. This button connects or disconnects the audio paths going to and from the remote end. It has the same effect as pushing the REMOTE BUTTON on the front panel of the EF200. ASPI Digital - The Sound of DSP Technical Support: 404. 892. 3200 A-17 EF1210 USER MANUAL PHONE BOOK Figure 30. EF200 Phone Book on EFPanel Control Software DIAL. [. . . ]