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Gunshot Tracking Cameras to be Deployed in LA
apok04 writes "Get out your tinfoil hats (and ski masks). A USC engineer uses his expertise with nerve cells to create a surveillance system that can recognize the sound of a nearby gunshot - and identify the shooter. In a unique pilot program, L.A. and Chicago will deploy test units in high-crime areas. The creator emphasizes that the system cannot recognize voices or words, but his previous research into speech recognition systems suggests otherwise."
The profile for a voice is much different from that of a gunshot, and creating a multi-purpose system to do this would make both perform much worse.
Also speech recognition knowledge is very different from speaker recognition (one cares about what the person says regardless of how they say it, the other cares about how they say it regardless of what it is). The mathematical models for both are very different.
Also the microphones are likely specialized in the wrong frequency/volume range to be useful for speaker authentication.
1917 ish. Somebody in the Canadian Expeditionary Force to WWI figured out how to accurately direct counter artillery fire using two human ears, a telephone and some trigonometry. The Germans never did figure out why they couldn't fire more than a round or two before they got nailed.
Here's an evaluation. Median location error is about 25 feet. That at least gets it down to two or three houses.
I met the designer of this system some years ago. The original prototype worked using microphones and hard-wired phone connections for each microphone. The signal from each microphone was transmitted using an analog FM carrier system over the phone line designed to trade frequency response for dynamic range. The system had terrible audio frequency response but huge dynamic range, so that pulse events like gunshots come through cleanly without overload. When you have enough dynamic range, gunfire is easy to recognize, because the leading edge of the pulse is so sharp. Few other sounds have that form.
The microphones are up on telephone poles and atop buildings, and they're omnidirectional. So they mostly pick up loud bangs, wind, and aircraft noise. The original pole units were entirely analog, phone line powered, and very dumb. The original central processing system was a PC with some data acquisition cards running LabView. Since then, it's become fancier, with better integration with mapping programs and transmission of gunfire locations to PDA-type devices. But it's not really very complicated.
In English, we do not posess a grammatical gender to refer to the unknown: we have male, female, and neither, but not a possibly-either. The convention in English for nearly two millennia, and in her precursor languages (English is grammatically feminine, incidentally, much like a ship), has always been to use the masculine when referring to the unknown or the general. That is, the masculine gender serves double duty: it (amusingly, the masculine grammatical gender is itself grammatically neutral) refers to both males and other grammatically-male individuals, but also to those whose grammatical gender is unknown or general. This isn't sexist so much as a limitation of the language. Incidentally, the very word 'man' is actually a gender-unknown holdover from Old English; the word for a male man (a phrase which seems redundant now) was 'were' (like werewolf, and pronounced similarly); because 'man' could refer to either a man or a woman, words like 'wifman' (means wife-man), which became 'woman,' or 'leman' (a mistress: means love-man) could be formed.
Moreover, in this specific case the distribution of male vs. female shooting perpetrators can hardly be said to justify the use of the feminine. Quite the opposite, really.