Setting up the Automatic Gain Control for sound cards of Olha line

Automatic Gain Control (AGC) is designed to make the audio signal volume constant. AGC mechanism should be set only with the use of sound cards of Olha line : Olha-9P, Olha-10LP, Olha-12U, Olha-14.

It is recommended to use AGC when input audio signal power is unsteady or when the power of the sound signals, coming from different sources and forming the joint audio signal, differs significantly. AGC levels out the power levels of audio signal components from different sources.

Axxon PSIM™ software has an AGC adjust option. AGC has two adjustable parameters: a target power level, to which AGC brings different audio signals, and the adjustment time of bringing the signal to the target power level. The second parameter has certain restrictions: the less time it takes to bring the signal to a certain power level, the lower the quality of AGC operation, which may result in greater power level jumps in the processed signal. However, a longer adjustment time lengthens the areas where the power of the processed audio signal builds up and decreases. So, processing may bring sizable distortions into the audio signal. Hence, AGC settings depend substantially on the conditions of audio signal formation, and when these conditions have been changed, new AGC settings should be set.

AGC is independently applied to any audio signal from any microphone of the video surveillance and audio monitoring system.

By default, AGC is disabled. The AGC option is enabled for each microphone independently.

To set up the AGC follow the steps:

1. Go to the settings panel of Microphone system object.
   
2. Set the Enable checkmark in the AGC group (1).
3. As a result, sliders in the AGC group Dinamic range and Time constant are activated (2,3).
4. Set the Dynamic range slider to the position, corresponding to the desired level of video signal’s output power. The current power value, measured in decibels, is shown in the field on the right of the slider (2).
5. Set the Time constant slider to the position that corresponds to the time of bringing the signal to the defined power level. The value of the time constant in seconds, set by the slider, is displayed on the right of it (3).
6. Click the Apply button to save all the changes (4).
7. It is recommended to check AGC correctness after the settings were made. To do so, use one of the audio playback devices of the Axxon PSIM ™ software, for example, Audio player object. Audio player should be preset for audio signals playback.
8. If audio signal power is too high, move the Dynamic range slider some points to the left. If audio signal power is too low, move the Dynamic range slider some points to the right.
9. If increasing and decreasing of audio signal power is perceptible, move the Time constant slider some points to the left. If significant jumps in audio signal power are perceptible, move the Time constant slider some points to the right.
10. When necessary, repeat 7-10 steps. If AGCis set up correctly, finish AGC setting up procedure.

AGC setting up is completed.