Unlike conventional gate plug-ins, smart:gate is not controlled by the overall level of the input signal, but by the activity of a selected target source.
After selecting a profile, the green Activity Function (which serves as the control signal for the gating) only shows the activity of signal components belonging to the selected target source. This means that if no source has been detected, the Activity Function will remain at zero.
The Level Bias parameter allows to fine tune the shape of the Activity Function:
With a high level bias, the activity function follows the level of the target signal. So, the gate works level based - it opens or closes depending on the exact level of the target signal.
With a low level bias, the Activity Function displays high values as soon as a low level of the target signal has been detected. So the gate works more or less level-independent – it opens or closes as soon as a target signal is detected (no matter how quiet it is).