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Comment by rmason | Hacker News Reader

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rmason·

They need to deploy a shot spotter that cities use to quickly locate gunfire and dispatch police.

https://www.forbes.com/sites/alexknapp/2013/06/28/shotspotte...

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With laughable accuracy: http://fox61.com/2013/05/22/fox-ct-investigation-is-costly-g...

Part of the problem is multipath due to reflections caused by buildings, hills, trees, etc. Anytime you listen to thunder or fireworks the rumble persists due to reflections off of such things. It's incredibly difficult to algorithmically remove multipath from terrestrial sources.

Correct. At 30 Hz directionality is a pipe dream.

It's relatively trivial to find direction of the 30 Hz sound source, given 1 million budget - you just need to place microphones 11 meters apart and raise them above buildings until you get direct line of sight to the main source.

A million bucks wouldn't get a square city block of what you describe.

A square block? 5-10 microphones is plenty. Your goal is to find a direction from the place you deploy, not to blanket the city. Then you can redeploy somewhere else to get another direction, etc.

That's an example of how poor directonality is at 30 Hz.

I'm always disappointed to see that people think the description on that system's tin is its actual purpose. It does that, yes. What else?

That's some scary stuff right there. Who controls what it's used for? How transparent are the data? Yikes!

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