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Design Guide for the Polycom SoundStructure C16, C12, C8, and SR12
7 - 12
For example, a common tabletop microphone has a sensitivity of -27.5
dBV/Pa. which translates to an input gain of 48dB.
Room Gain
Room gain meters are used to measure the relative level of the remote audio
that is present at the input to the AEC with the level of the echo that is present
at the microphone. For more information on room gain and how it is mea-
sured, see Appendix B.
The room gain meter is shown on the AEC portion of the input channel on the
channels page as shown in the following figure. The meter segments show the
room gain ranges in 3dB increments from -10 to +20dB. The first segment of
the meter is lit if the room gain is greater than -10dB and less than or equal to
-7, and so on through the meter segments. The last meter segment will illumi-
nate if the room gain is greater than 17dB.
Sensitivity (dBV/Pa) Microphone gain (dB) Sensitivity (mV/Pa)
-50.0 70.0 3.2
-48.0 68.0 4.0
-46.0 66.0 5.0
-44.0 64.0 6.3
-42.0 62.0 7.9
-40.0 60.0 10.0
-38.0 58.0 12.6
-36.0 56.0 15.8
-34.0 54.0 20.0
-32.0 52.0 25.1
-30.0 50.0 31.6
-28.0 48.0 39.8
-26.0 46.0 50.1
-24.0 44.0 63.1
-22.0 42.0 79.4
-20.0 40.0 100.0
-10 -7 -4 -1 2 5 8 11 14 17