A school in Massachusetts tested a gunshot detection system by Shooter Detection Systems. Here is the article.

The system works by installing smoke alarm sized devices in rooms and hallways. It picks up the report of a gunshot and muzzle flash then relays that information to track and help locate the active shooter.  One thing they do not mention is if it can pick up gun shots fired through a suppressor. Or in the case of my KRISS Vector with its long 16″ barrel, there is no muzzle flash. What does the system do then?