TROUBLESHOOTING
In-Conference Quick Check
Excessive
Microphone
Amplification
talker to the microphone. The microphone audio will most likely also be muddy and reverberant. The installer or user may try to solve these microphone audio quality problems by turning up the microphone amplification, thus adding to the room gain. This problem can be remedied by proper microphone selection (pickup pattern, directionality) and placement, coupled with proper microphone input calibration.
3.A third common cause of room gain problems is excessive coupling between loudspeaker audio and microphones. This can be addressed by reducing the microphone coupling, either by positioning microphones so that their pickup pat- terns are biased away from the loudspeaker audio (and direct reflections of loud- speaker audio), repositioning loudspeakers, or reducing the loudspeaker amplification.
In summary, any amplification applied between the reference input and the micro- phone inputs can add to room gain problems. To avoid problems, ensure that the Ref- erence input signal is not too low, and the microphone input signals are not too high. Run the
COMMON CAUSES OF EXCESSIVE | REMEDY |
ROOM GAIN |
|
|
|
Excessive remote (reference) input | Apply enough gain to the codec, phone |
amplification | or program audio inputs which will |
| make up the Reference input signal. |
|
|
Excessive microphone amplification | Select proper microphones for talker |
| distance according to pickup pattern |
| and directionality and properly cali- |
| brate mic inputs. |
|
|
Excessive coupling between loud- | Reduce mic coupling by repositioning |
speaker audio and microphones | mics or loudspeakers, or by reducing |
| loudspeaker amplification. |
|
|
Table 3: Summary of Excessive Room Gain.
If you experience residual echo problems during a conference, you can quickly check that the reference and microphone levels are calibrated and not causing room gain problems by using the Room Gain parameter (See “Verify Room Gain” on page 14).
If this excessive coupling activity level is evident on only one microphone input chan- nel, that microphone channel should either be redirected to reduce coupling to loud- speaker 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 recali- brated (this will be indicated by observing low activity levels on the SIGNAL LEVEL METER).
For the EF2241 to adapt effectively, saturation (overload or clipping) must not occur at the A/D converter supplying the microphone input. Saturation introduces nonlin- ear signal distortions into what the AEC expects is a linearly echoed version of the remote speech.
© Polycom, Inc. | 41 | VORTEX EF2241 Reference Manual |
