Active Audio SA100P, Manual

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11.2 Check connected processors
11.2 Check connected processors
Already inited processors don’t show up automatically in SAdrive. To discover those processors, follow the steps
below:
Connect to COM port.
1 2
Discover from harware setup.
12 Advanced functions
12.1 Automatic gain control: AGC
Automatic Gain Control is available if the UT26 processor is equipped with the MIC option (section 5.1 ).
AGC allows automatic adjustment of the diffusion level according to the sound level captured by the microphone
when no message is played. Using this function, the sound level perceived by listeners is adjusted for optimal
comfort: moderate level when the ambiant noise is low, higher level when the ambiant noise is high in order to
provide good intelligibility.
The amplitude of the ambiant noise captured by the microphone is smoothed with a time constant adjustable by
the user. This resulting smoothed value is used as a basis for gain calculation: below a threshold adjustable by the
user, the AGC gain is set to
0
dB ; above this threshold , the AGC gain increases proportionally to the ambiant noise
up to
+12
dB
.
For example:
• If the ambiant noise is
75
dB
SP L
and the AGC enters in action ( Threshold ) at
65
dB
SP L
, then the AGC gain
will be
10
dB (i.e.
75
dB
−
65
dB ).
• If the ambiant noise is
80
dB
SP L
, and the AGC enters in action (Threshold) at
65
dB
SP L
, then the AGC gain
will be
12
dB (i.e.
80
dB
−
65
dB
= 15
dB but AGC gain is
12
dB max) .
The AGC algorithm is summarized on figure 21 .
AGC gain (dB)
Ambiant noise
(dB spl)
Threshold Thr 12dB
0
12
Figure 21: Automatic gain control functional graph
Last update: December 23, 2010
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