The best counter sniper system is another sniper. However, a number of sensor systems can be and are providing useful tools in dectecting, locating, and bringing effective fires on snipers.
Some of these technologies seemed hairbrained at first. Some of them proved to be just that. But, others have met the test of both time and combat. The jury is still out on this device. The Army's Rapid Equipping Force conducts in theater operational assessments on technologies like these. Some of them end up in the scrap heap, but others get adopted and deserve to be. I'm sure you haven't seen the data on this, but if you did you might change your mind. Acoustic sensors have come a long way in the last four years.
“I’m sure you haven’t seen the data on this, but if you did you might change your mind”
And you would be wrong. I have seen the acustics data of such devices. Signals processing is a thing I am an expert. I know the issues and these devices have issues. Alert, well trained troops far beat having yet another device they are told to rely on but will fail them.
The counter sniper devices that do work are the MMW systems. Those devices work because they detect the round from nearly the barrel to the target. They can not only trace where the round came from but its type as well.