60
TANDBERG Videoconferencing System
Advanced use
Automatic Gain Control (AGC) Settings
Select ‘
On
’ to allow automatic adjustments (Automatic Gain Control) of audio levels. When ‘
On
’, the AGC
maintains the audio signal level at a fixed value by attenuating strong signals and amplifying weak signals. Very
weak signals, i.e. noise alone, will not be amplified.
Example:
In most conferences, the participants will speak at different levels, and be at different distances from the
microphones. As a result, some of the participants would be harder to hear than others. The AGC corrects this
problem by automatically increasing the microphone levels when “quiet” or “distant” people speak, and by
decreasing the microphone levels when “louder” people speak.
When applying a weak signal in the presence of strong background noise, the AGC might amplify the background
noise as well as the signal. Therefore, in noisy environments, it is advisable to turn the AGC off.
Tips for improving the echo canceller performance:
• Place all microphones as far as possible from the loudspeaker. Minimum loudspeaker-microphone distance
should be 1 meter.
• Place all microphones as close as possible to the persons speaking. By using several microphones, the ratio
distance loudspeaker-to-mic/mic-to-speaker can be increased. Increasing this ratio improves the echo canceller
performance. Avoid distances above two meters from any participant to his/her closest microphone. If
necessary, use several microphones. Also avoid placing microphones less than one meter from any person.
• Place all microphones as far as possible from noise sources.
• Reduce the volume setting. Ensure that the loudspeaker does not distort the audio.
T
O
ENSURE
CORRECT
BEHAVIOUR
OF
THE
AGC,
IT
IS
CRUCIAL
THAT
THE
LEVELS
ON
THE
INPUT
CONNECTORS
ARE
ADJUSTED
CORRECTLY
USING
THE
AUDIO
INPUT
LEVEL
SETTINGS
. T
HE
AGC
WILL
NOT
COMPENSATE
FOR
SEVERE
MISADJUSTMENT
OF
INPUT
LEVELS
.
NOTE
