ShotSpotter cannot be "unlocked" to record conversations by accident. These sensors are placed far away from where people might be talking and this is intentional. Conversations are just one more source of noise to be filtered out.
This is no different from modifying the nude scanner at the airport to display a generic human form rather than the actual outline of your body. The machine still has the capacity to display what your private parts look like.
You could hear the firing pin hitting the cartridge (harder to hear than engine running) then you should hear the gasses exiting barrel somewhere around 0,001 second later. Then calculate doppler... Sounds kinda hard.