Something that lets me select a frequency above which all sounds would be filtered in real time? I don’t know if a software can separate the high pitched sounds from the rest of the sounds. If it was possible that would be perfect. If not just removing all sounds when any sound goes above the threshold.
It is not entirely clear what exactly you want, filter is just a common term in the audio scene… what to filter … remove frequencies or to reconstruct original sound. This is a difference.
If your goal is to lets say, filter frequency under 200 Hz to filter keyboard noise, equalizer APO would do, it is better than OBS Studio plugins because it uses a driver which works at lower latency without disorientation.
What do you mean “police uses”? Why is that relevant?