Applications of math: current events
10-11-2017, 01:35 PM
Post: #1
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
Applications of math: current events
If nothing else, we have a real story problem, with real consequences. Can the application of math reveal the path of evidence, that leads to the real facts?

-Dale-
10-11-2017, 02:02 PM
Post: #2
 webmasterpdx Senior Member Posts: 541 Joined: Sep 2015
RE: Applications of math: current events
Interesting problem. There are issues with this analysis though, such as echos, were all the rounds the same type, external noise, etc, etc..
10-11-2017, 02:22 PM
Post: #3
 SlideRule Senior Member Posts: 1,254 Joined: Dec 2013
RE: Applications of math: current events
REAL facts? I recommend at least a casual perusal of references such as ...

[attachment=5238]
or
[attachment=5239]

BEST!
SlideRule
10-14-2017, 01:12 AM
Post: #4
 Claudio L. Senior Member Posts: 1,709 Joined: Dec 2013
RE: Applications of math: current events
(10-11-2017 01:35 PM)DrD Wrote:  If nothing else, we have a real story problem, with real consequences. Can the application of math reveal the path of evidence, that leads to the real facts?

-Dale-

Yeah, not once he mentions the location of the recording device in his little analysis. The simple calculation from lag time to distance traveled by the bullet is only valid if the recording device was at the point where the bullet hit the pavement or very close. If the recording device was not there it's all wrong.
Imagine the recording device half way between the shooter and the point of impact. The sound of the muffler travels only half the distance, while the sound of the impact also travels half the distance (back). As an extreme, if the recording device is close to the shooter, you'd hear the sound of the muffler before the sound of the bullet hitting the pavement, so this guy's conclusion would be that a second shooter is shooting standing on the pavement, shooting down into the pavement so the bullets bounce and fly back into the barrel of the other guy's gun.
10-14-2017, 10:49 AM
Post: #5
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
RE: Applications of math: current events
I understand your thinking. There is usually no shortage of conspiracy theories at times like these. Right or wrong, he does say that there were several recordings, captured on different cellphones, that formed the basis for his audio analysis.

This subject underscores what Norman Schwartzkopf, (desert storm), was talking about using the term, "fog of war," when trying to get facts and fiction sorted out.

The idea presented, using audio analysis as a tool for locating the position of a shooter, set my mind to wondering if a weapon mounted device could be created for military/police personnel to use to help locate enemy shooters on the battlefield.
10-14-2017, 01:58 PM
Post: #6
 webmasterpdx Senior Member Posts: 541 Joined: Sep 2015
RE: Applications of math: current events
They probably already have such devices....
10-14-2017, 04:28 PM
Post: #7
 pier4r Senior Member Posts: 2,067 Joined: Nov 2014
RE: Applications of math: current events
(10-14-2017 10:49 AM)DrD Wrote:  The idea presented, using audio analysis as a tool for locating the position of a shooter, set my mind to wondering if a weapon mounted device could be created for military/police personnel to use to help locate enemy shooters on the battlefield.

https://en.wikipedia.org/wiki/Artillery_sound_ranging

Wikis are great, Contribute :)
10-14-2017, 05:00 PM (This post was last modified: 10-14-2017 05:18 PM by StephenG1CMZ.)
Post: #8
 StephenG1CMZ Senior Member Posts: 870 Joined: May 2015
RE: Applications of math: current events
I seem to recall reading of similar applications being investigated for use in city centre shooting, with the aim of detecting and locating gunfire.

https://en.m.wikipedia.org/wiki/Gunfire_locator

But one cannot really experiment with such algorithms on the HP Prime, which hasn't a microphone...though perhaps in conjunction with a Datastreamer?

[I've expertise in implementing software for guidance to target, and displays...]

Stephen Lewkowicz (G1CMZ)
ANDROID HP Prime App broken offline on some mobiles
10-14-2017, 05:04 PM
Post: #9
 John P Member Posts: 193 Joined: Dec 2013
RE: Applications of math: current events
(10-14-2017 01:12 AM)Claudio L. Wrote:
(10-11-2017 01:35 PM)DrD Wrote:  If nothing else, we have a real story problem, with real consequences. Can the application of math reveal the path of evidence, that leads to the real facts?

-Dale-

Yeah, not once he mentions the location of the recording device in his little analysis. The simple calculation from lag time to distance traveled by the bullet is only valid if the recording device was at the point where the bullet hit the pavement or very close. If the recording device was not there it's all wrong.
Imagine the recording device half way between the shooter and the point of impact. The sound of the muffler travels only half the distance, while the sound of the impact also travels half the distance (back). As an extreme, if the recording device is close to the shooter, you'd hear the sound of the muffler before the sound of the bullet hitting the pavement, so this guy's conclusion would be that a second shooter is shooting standing on the pavement, shooting down into the pavement so the bullets bounce and fly back into the barrel of the other guy's gun.

I watched the video on YouTube. Yes, he did not mention where the mic was placed, but his presentation implies, sort of, that the mic was close to where the bullets were hitting the pavement. The mic must have been close to that place because many people in that are were filming the situation and recording the sounds. If the filming and the recording was done from far away the mic would not picked up the sounds of bullets hitting the pavement. Yes, it would be better if the guy on the video who presented his discovery indicated where the mic was located, but I do not think that that was a major fault on his part. He can correct it very easily. The YouTube presentation was interesting and intriguing.
10-14-2017, 05:31 PM (This post was last modified: 10-14-2017 07:30 PM by DrD.)
Post: #10
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
RE: Applications of math: current events
With many cell phones acting as microphones, the "basic setup" mentioned in the wiki, that pier4r provided, is pretty well covered. I think a mathematical analysis, including doppler corrections could compensate for not having ideally located microphones. Sound software such as sound forge, would be useful to get the timing just right, as well as remove artifacts that might be interference. I guess there was a helicopter in the area at the time, so the rotor blades might add a layer of confusion there, as well.
10-14-2017, 07:15 PM
Post: #11
 Claudio L. Senior Member Posts: 1,709 Joined: Dec 2013
RE: Applications of math: current events
(10-14-2017 05:31 PM)DrD Wrote:  With many cell phones acting as microphones, the "basic setup" mentioned in the wik,i that pier4r provided, is pretty well covered. I think a mathematical analysis, including doppler corrections could compensate for not having ideally located microphones. Sound software such as sound forge, would be useful to get the timing just right, as well as remove artifacts that might be interference. I guess there was a helicopter in the area at the time, so the rotor blades might add a layer of confusion there, as well.

Yes, if you could get the exact location of each recording device, and if you could time-sync the recordings. In the real case, many of the phones were moving, as people were running away, which makes it much harder to pinpoint where they are at any given time. Also, the time of the recording would have to be synchronized somehow between devices, perhaps looking at a frame of the video with the same event happening, but it would be really hard to get 2 or 3 valid recordings to use (with well-defined location, not moving and where you can time-sync the signals).
You also need to know where the bullets were hitting. Different recordings might be picking up bullets going to one or the other side of the arena. We are talking potentially 91m (100 yds) distance between the bullet-hitting point from one end to the other of the place.
Once you get that good data (if it exists), then you can start doing numbers and making conclusions using procedures like the ones Pier linked. Without complete and consistent data it's nearly impossible to draw any (meaningful) conclusions. Certainly not by doing simple arithmetic like this guy did.
10-14-2017, 07:29 PM
Post: #12
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
RE: Applications of math: current events
Pinpointing the microphones can be done by measuring the delta time between them and the source, taking into account the various time delays. It may be practical to average the latency of the sound differentials, and sort of average out those offsets.
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