Gun shot detectors
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March 4th, 2011 at 12:09 pm
I already have some of those. ‘Cept mine are called ‘ears’
March 4th, 2011 at 12:10 pm
Damn, Robb beat me to it.
March 4th, 2011 at 12:26 pm
It’s interesting that they say they can give a range as well as bearing. I can see doing that by measuring the time between the sound of the bullet passing (sonic boom) and the muzzle blast or by measuring the volume of the muzzle blast. But these don’t work unless you also have a baseline for that round and maybe you can teach it what different common rounds sound like, but it sure sounds like a SWAG.
March 4th, 2011 at 1:17 pm
Not a SWAG, simple (although microelectronically marvelous) triangulation. Several detectors on different folk triangulate the origin of the shot and the errors in absolute position of the wearer and the origin of the shot essentially cancel out with more and more detectors.
GPS with less than 1 meter accuracy is a useful thing.
March 4th, 2011 at 2:16 pm
I wonder if it can detect the bullets that go through it???
March 4th, 2011 at 4:17 pm
@Robb – Sure, the human ear and brain combo is a marvelous direction-finding apparatus; as long as the brain isn’t confused or overloaded by input, or the sound isn’t subject to multipath interference or other masking effects.
@Andrew, @Mikee: you don’t need multiple people if the system has stereo receviers. It works the same way your eyes let you estimate range. Without seeing his other shoulder, we can’t say one way or another. But I can note that the mikes are likely the cheapest component of the system.
Also, I finally see the need for the line-in jack on electronic ears. I mean, sure, it’s handy when *I* want to mow the lawn and listen to some tunes; but I wasn’t sure that was why the manufacturer put them there.
Actually, I rather like using my electronic ears as earphone for my MP3 player even if I don’t need hearing protection – I lose less aural situational awareness, IMHO, that way than if I use earbuds.
March 4th, 2011 at 6:33 pm
Robb: Ears require training.
Until the Marines returned to manually setting targets in traps, and thus giving recruits experence in the sounds made, fresh Marines in Iraq and Afghanistan were turning their rifles towards the sonic crack of the bullet going by.
And pointing 90 degrees off the real source of the shot.
March 4th, 2011 at 10:28 pm
With two mics there would be a cone of confusion – inability to know if sound equidistant to both was in front or behind. With four mics in a tetrahedron you pretty much eliminate ambiguity in direction, and one probably can get away with three mics if you assume that your zone of detection is a hemisphere, not a full sphere (i.e.: the detector is attached to someone standing on the earth, not suspended in free space above it).
Distance can be detected by estimating the curvature of the wave from the time of arrival at the three mics — as distance approaches “really far”, wavefront becomes “plain”. The closer the source, the rounder the wavefront of the pulse. Although would be much easier to gauge range by triangulation between many spaced personal detectors, I don’t relish the thought of all our guys wearing a little bluetooth that is constantly broadcasting “these are my GPS coordinates, what are yours” each time it hears a gunshot.
March 4th, 2011 at 11:22 pm
Depending on the trajectory, my t-shirts would make pretty good shot detectors. Depending on proximity, my underware would detect a shot too; although you wouldn’t be able to determine shot direction.
March 5th, 2011 at 12:54 am
Yeah, but that’s a one-time use of otherwise valuable underoos.