That's not the worst of it. Consider the full implications here. Imagine a worst case scenario where gunshot detection is used as a pretext to put microphones all over city streets, every block say. Now imagine that those recordings are stored forever and properly time / location tagged, not a technologically difficult problem.

Then imagine what is possible with such data. First off, you could use triangulation and advanced filtering between multiple microphones to be able to pinpoint the source of each sound and separate it out from the background. You could, as you say, identify individuals by their voices. You could track their wherabouts. You could monitor who they are talking to and when. You could learn so much about their lives by monitoring all of their conversations in "public". In the worst case scenario of the government turning into a police state this is a frightening level of surveillance.

Apart from the fact that the devices are apparently designed not to be capable of recording conversations, and can clearly be improved to make it even more difficult to record conversations, "not deploying gunshot detection" isn't the only privacy control that cities can employ; cities can just make it illegal to collect raw audio.

The article mentions that the devices did manage to record conversations in at least one case. If so, they are clearly capable of recording conversations, just not optimized for it.

Also, how do you distinguish gunshots from background noise and triangulate the location of shots without first collecting raw audio from multiple devices and analyzing it?

Indeed, there's clearly some disinformation going on in the article:

"James G. Beldock, a vice president at ShotSpotter, said that the system was not intended to record anything except gunshots and that cases like New Bedford’s were extremely rare. “There are people who perceive that these sensors are triggered by conversations, but that is just patently not true,” he said. “They don’t turn on unless they hear a gunshot.” "

So apparently "the sensors", "They don’t turn on unless they hear a gunshot.". How, exactly, do they "hear a gunshot" if they're not (yet) turned on?

I suspect the truth is there's some software configuration that inhibits _recording_ of the sensor data until a gunshot-like event occurs (though if _I_ were designing this system there'd be at least a 30second or so buffer, so I could archive the sounds that if heard _before_ a gunshot as well as afterwards). But I'd hesitate trust that "configuration" to be particularly secure - much like the TSA "pornoscanners" - which in spite of claims of it being impossible, seem to be able to record images for the amusement of the operators and their friends…

They could be designed to run some local preprocessing and only record/forward audio when a gunshot seems significantly probable. (Not that I'd bet they actually do. We need public pressure to get them made that way.)

If I recall correctly, privacy laws are based more on reasonable expectation of privacy rather than where the recording device is located. I can't climb a telegraph pole and photograph someone inside through a second floor window, for example.

I don't know how this would affect the legality of surveillance though.