@pk2019, no I did not realize that. The file I used is called “LEO montage - Cruiser + Why not on roof.mp4”. I downloaded it from a Mega link that someone posted on this forum. It only has one audio stream in it. Where do I get the original video that has all three streams?
Experiment worth doing…
- Calculate (approx) circumference of Crook’s upper arm based on this photo:
- Find someone with same circumference and color of arm.
- Dress in same t-shirt.
- Arrange in pose as in following picture:
- Take photo from afar, zoom in, and compare.
- Buy skinny-armed model a few beers. (Happy to chip in).
The experiment would falsify the arm position as the reason for the apparent difference.
You’re right, but bear in mind that (1) they also depend on the strength (amplitude) of the sound; and (2) modern cellphone mics are omnidirectional and pretty good; (3) there were differences as well in the very non-directional bass frequencies.
You’re not going to get much of a difference walking a few meters recording gun blasts, even around a corner. But whether it is enough of a difference is valid, so good point.
It certainly is an odd coincidence! Greg Nichols (engineer) vs. Greg Nicol (cop). Life is interesting.
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Are you being serious?? lol
I swear half of these weird theories would disappear if people just chose to look at the evidence available to them lol
Wow, @vt1 . Thanks for doing those calculations. Just to be clear, you use the estimated speed of the bullet to determine the angle of the sonic cone. From what I’ve read, the internal angle of this cone decreases as the bullet’s speed increases past Mach 1.
Let me make sure I understand all the variables in Eq. 12
b = distance from shooter to the closest point of approach to the audio recorder
Vm = muzzle velocity
h = distance from the recorder to the bullet’s path of travel
Vc = speed of sound
If we go to Matthew Pearson’s Dropbox you’ll see an “audio” looking icon in the lower right that lets you select tracks.
We’re not sure where the mics are. They might be front cabin (we’re probably hearing air conditioning) and rear cabin (to record what suspects say) and something else, not sure.
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Thanks, @brian60221. I downloaded the MP4 and can see that it has three tracks. The sounds at 5:27 when he is getting the rifle out from the rear compartment tell me that the tracks are:
- Second row
- Front seats
- Rear compartment
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As I have already stated several times, my analysis shows that if it is 55 or even 62gr, then the velocity is substantially higher for either 223 or 556 rounds. And then the snik-report difference would prove conclusively that the shots came from much closer (like 410 or 420ft). Which would mean TWO SHOOTERS.
The ONLY way that it could be ONE shooter is as I showed in my post with an average velocity of 2644 fps or less. That means 77gr round most likely.
WE NEED TO KNOW WHAT THE BULLETS WERE.
All the rest of this multi-mic nonsense is not useful.
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Yes @greg_n your understanding is correct. The sound traveling in the air can be interpreted like waves of pressure differential. If the bullet travels at higher speed than the sound speed these waves are superimposed creating the shock wave. The angle formed define the proportion of the bullet speed and sound speed, that travels perpendicular to the shock wave. The sine of the angle is equal to that proportion, the inverse of that is the mach number. Tracing back from the reciver the shock wave that arrived there must have come perpendicular to that wave therefore it came from point 1, the distance 12 is the distance travelled at sound speed. At the same time the bullet travells from point 1 to point 3 at the bullet speed forming the rigth triangle 123. The shock wave total time is the time for the bullet to arrive at point 1 plus the time for the sound from point 1 to point 2. The report time is the time for the sound to go from the muzzle to point 2.
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I plotted all the shot positions that have been proposed and found only Crooks position (and possible 2nd shooter in the building/ceiling below) aligned with the ear and puff of smoke at the top right rear bleacher.
I then looked at the alignment of two trajectories (from Crooks and from a second shooter ceiling position below Crooks) and compared them the famous photo of the bullet trail next to his head.
And found a perfect match. I see only two possible trajectories that work. Crooks and an above the ceiling position shooting out of a vent hole. The vents can be seen in photos.
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Greg, I’m unsure what you mean by “Second row”.
It might be like you say. Yet stream 1 and 3 are always 10 ms apart, with stream 2 in between. There are numerous examples, beginning with undercarriage noise and further on with the firstly only intended door opening and various clicking sounds as well.
Overall, I now see that delay as a systematic error within the video/audio documentation system of that patrol car. Please see also my post here.
I did some superpositions of images from RSBN.
Line blue - from Crooks
Line orange - from the vents.
I’m more inclined to think it came from Crooks.
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Your line of fire paralleling a vapor trace of the second projectile may do so only apparently, depending on how you correct for the perspective distortion. You may want to follow the discussion of my own approach here
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Why is the orange line parallel to the blue line? It should angle up and hit his hear.
It’s not parallel, it’s hitting the same point the south bleacher.
The quality of image is very poor here.
Doing your scenario it does not hit the rail.
In this post also concluded the same think from James Copenhaver footage.
If the line of sight from James Copenhaver footage is almost aligned with Trump ear and the Vent that means that a fire from the vent would pass at the height of the camera eyepiece. Therefore, if the bullet hit the rail it has come from an upper position.
I also explained that here to @roger-knight, where I did a model correcting Google Earth height using James Copenhaver footage.
In his opinion I cannot use the footage for the model, but I think that it still proves it did not come from the vent, but from an upper position.
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@cohler No, the multi-mic approach is very useful. While it does not answer all of the questions, it does tell us that Shots 1-8 all came from the same location, within a 1 meter radius.
Without time-synced recording sources, TDOA cannot provide the absolute location, but if you believe that any of the 8 shots came from the crooks position, then all 8 of them came from that same spot.
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I feel like listening to all the different audio sources that was pretty apparent, but at least we have data to back it up now since people’s ears don’t work.
Just to be clear, for this model to work I had to choose an initial condition to define the location of one of the shots. Without time-synched recording sources I had no other choice. So, I picked the crooks location and saw that the other 7 shots came from that same place. It doesn’t matter which of the 8 shots I choose to be the initial value, the results turn out the same.
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