There is a system displayed on the ZhuHai air show this year using highly sensitive microphone to detect where the enemy sniper shots or mortar fires form, im not sure how exactly these types of equipment works but i could take an educated guess that the characteristics of sound of certain enemy's weapon maybe the key element or at Least it could make the work a bit easier considering how chaotic the real battlefield would sound like.
I doubt it’s going to work that way as all sorts of environmental factors can affect the sound profile in the real world.
Doing a sound library would also require you to have a comprehensive recording of all sound signatures of all weapons types, then you need to factor in different ammo types and suppressors etc, which feels like a recipe for disaster.
I would think that if they were to use sound libraries, they would instead feed in the sound profiles of all PLA infantry weapons so the system automatically exclude those from the analysis.
But I think such systems will work best for forces like peacekeepers, who might get shot at occasionally rather than troops operating in the middle of pitched battles, as I imagine the system will probably be overwhelmed or produce so many tracks as to be largely useless during intensive firefights.