Setting up the automatic gain control for sound cards of Olha series

The automatic gain control (AGC) of the audio signal is used to bring the volume of the audio signal to a constant level. You can configure the AGC mechanism only when you use sound cards of Olha series: Olha-9P, Olha-10LP, Olha-12U, Olha-14.

 You can use the AGC mechanism in conditions of uneven power of the incoming audio signal or when the power of audio signals coming from different sources and forming the aggregate audio signal differs significantly. The AGC mechanism levels out the power levels of audio signal components from different audio sources.

Axxon PSIM provides a possibility to configure the AGC mechanism according to the operating conditions. The AGC mechanism has two adjustable parameters: the power level, to which the AGC brings both more and less powerful audio signals, and the time to bring the audio signal to the specified power level. The second parameter of the AGC mechanism has the following limitations: the shorter the time to bring the audio signal to the required power level, the lower the quality of AGC operation and the greater the power level fluctuations in the processed signal. At the same time, increasing the time of bringing the audio signal to the required power level lengthens the areas where the power of the processed audio signal builds up and decreases. Thus, processing can bring sizable distortions into the audio signal. Due to these circumstances, the values of AGC mechanism parameters depend to a great extent on the conditions of audio signal formation, and you must configure the AGC again if they change significantly.

The AGC mechanism is applied to each audio signal coming from any microphone of the video surveillance and audio monitoring system.

By default, the AGC mechanism is disabled. You must configure the AGC for each microphone independently.

To configure the AGC, do the following:

1. Go to the settings panel of the Microphone system object.
   
2. In the AGC group, set the Enable checkbox.
   As a result, the Dynamic range and Time constant sliders become active.
3. Move the Dynamic range slider to the position corresponding to the required level of output power of the video signal. The current value of the output power level in decibels is displayed to the right of the slider.
4. Move the Time constant slider to the position corresponding to the time of bringing the signal to the required power level. The value of the time constant in seconds is displayed to the right of the slider.
5. Click the Apply button to save the changes.
6. After you set the parameters of the AGC mechanism, we recommend checking the correctness of the settings. To do this, use one of the audio playback tools provided in Axxon PSIM, for example, the Audio player object. Beforehand, you must configure the Audio player to play audio signals.
   1. If the power of the audio signal is higher than the required power, move the Dynamic range slider a few divisions to the left. If the power of the audio signal is lower than the required power, move the Dynamic range slider a few divisions to the right.
   2. If you notice a rising or falling power level in the audio signal, move the Time constant slider a few divisions to the left. In case there is a significant power level difference for different periods of the audio signal being played back, move the Time constant slider a few divisions to the right.
7. If necessary, repeat steps 6a-6b. If the AGC mechanism is set correctly, complete the setting procedure.

Setting up the automatic gain control is complete.