Polycom C16 - Manual (Page 115)

Customizing SoundStructure Designs
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nals so that the average signal level is close to the SoundStructure nominal
signal level of 0 dBu. The AGC processing can be used on any input signal.
AGC is typically used on microphone input signals to compensate for local
talkers that are different distances from their microphones or telephone input
signals to compensate for varying telephone levels. The AGC system has been
designed to adapt the gain only when valid speech is present.
The AGC can be turned on or off with the AGC enable button. When the AGC
is enabled, the current AGC gain (or attenuation) can be viewed from the AGC
meter and the text box next to the AGC meter.
The range of the AGC can be adjusted by expanding the AGC control and
adjusting the maximum and minimum gains. By default the maximum and
minimum gain are set to 6 and -6 respectively on microphone and telephony
signals.
The maximum AGC value specifies the maximum amount of gain the AGC can
apply to increase the input signal level as the AGC tries to reach the Sound-
Structure nominal signal level.
The minimum AGC value specifies the maximum amount of attenuation the
AGC can apply to attenuate the input signal as the AGC tries to reach the
SoundStructure nominal signal level.
If the input is a stereo virtual channel, the AGC gain for both underlying left
and right physical channels will use the same gain, ensuring that the stereo
image is preserved.
To operate the AGC with a target level different from 0 dBu, set the AGC min-
imum and maximum range to the desired range and then adjust the input
fader to the desired target level above or below the 0 dBu nominal signal level
of the SoundStructure devices. This allows the AGC to adapt to the 0 dBu
nominal level and then the fader settings will offset the 0 dBu level to the set-
ting on the fader.
Dynamics Processing
Dynamics processors, also known as non-linear processors, are used to reduce
the dynamic range, or amplitude, of input or output signals and are often used
on sound reinforcement systems to prevent clipping audio amplifiers.
Dynamics processors are similar to automatic gain controllers, but are typi-
cally faster acting and can be used with program audio and other fast changing