@roger-knight, I spent a few hours using Audacity to examine the two videos we’ve been discussing:
- Source 3 / Ross! / TMZ
- Source 4 / Piper Grimley
I used a combination of viewing the spectrogram and using headphones with a 0.18x playback speed to listen carefully for gunshot echos and then mark them on the timeline.
TMZ Video
You identified an echo for shot 2 @ 0.083 second delay. Listening to this sound at slow speed, I’m not convinced that it’s a gunshot echo because it has a different sound from all of the other echos. Also, I don’t hear or see a similar echo for shots 1 and 3. Why not? However, what I do hear and see are echos at 0.122 and 0.167 for shots 1 and 3. I think we don’t see the same echos for shot 2 because they are drowned out by the lady’s scream.
TMZ Shots 1-3, with Slow Motion
Looking at shots 4-8, echos at 0.169 are strong and easily visible on the spectrogram except for the two cases (shots 6 & 7) where the timing between shots was too short for them to be seen. I also hear echos at 0.124 but I don’t see them on the spectrogram. Perhaps with different spectrogram settings they might become visible?
TMZ Shots 4-8, with Slow Motion
Summary: TMZ consistently has a strong echo at about 0.169 for all shots and a weaker echo at 0.124.
Source 4 Video
You pointed out Chris’s video where he says that Source 4 has an echo at about 0.080 for shots 1-3 and at 0.170 for shots 4-8. After my examination, I concur with @cmartenson that the only noticeable echo for shots 1-3 is at about 0.080.
Source 4 Shots 1-3, with Slow Motion
Looking at shots 4-8, I see consistent echos at about 0.163 which line up close enough with the 0.170 that Chris mentions for shots 4-8 and the 0.169 that I observed with all shots in the TMZ video. However, what Chris failed to mention in his video is that in addition to the echos at 0.170, we can also hear echos at 0.080 for shots 4-8 as well as see them in the spectrogram. So, it’s disingenuous to say “shots 1-3 have an echo at 0.080 and shots 4-8 are different because their echo is at 0.170”.
Source 4 Shots 4-8, with Slow Motion
Summary: Source 4 has an echo at 0.080 for all eight shots. It also has an echo at 0.163 for shots 4-8.
Why does Source 4 not have an echo at 0.163 for shots 1-3? I go back to my previous observation. For shots 1-3, Source 4’s smartphone was pointed away from AGR6 and the fenceline. For shots 4-8, it was swung around 180 degrees and pointed toward AGR6 and the fenceline. The most logical explanation is that when Source 4 was pointed away from the shooter there was sufficient attenuation (due to microphone direction and the person’s body being in the way) that the echos at 0.163 could not be heard. It should also be noted that between shots 3 and 4 Source 4 moved closer to TMZ, increasing his elevation and improving line-of-sight/sound to the shooter.
Sources of the Echos
In theory, we should be able to identify what is causing the echos to occur at specific times. It’s just a matter of figuring out which objects the gunshot sounds are bouncing off of and do the math for speed of sound, right? Well, have any of the Citizen Investigators published any work along those lines? I’m thinking probably not. Why? Because the geometries of this scenario make for an extremely complicated puzzle to solve. For example, even though the TMZ recorder was on high ground and far enough back to see Crooks lying on the roof, he still could not quite see the muzzle, right? Source 4 was lower and closer, so he definitely could not see the muzzle. If we don’t have direct line-of-sight to the muzzle then we also don’t have direct line-of-sound. So, what path did the sound take to get to the recorders? After pondering all of the possibilities for a while, it occurred to me that sound travels a lot faster through a dense material like steel than it travels through air. The rifle muzzle was close to the building’s roof, so the muzzle blast and sonic shock wave would have hit that steel pretty hard. Could such a sound wave be strong enough to propagate through the steel of the roof to the side wall, causing the side wall to act like a “speaker” and push a sound wave through the air to the recorders? The math for all of that was too complicated for me, so I asked Grok to crunch the numbers. Check out what he had to say:
Sound propagation through steel and air
Should I have been surprised when Grok’s answer was 0.079 seconds, only 1 millisecond off from the 0.080 echo observed in all of the Source 4 gunshots? I understand this approach may seem a bit far-fetched, but it’s the best explanation I have for the consistent echo at that time delta. It does beg the following question, though. Why don’t we see this same 0.080 echo on the TMZ recording? While I’m not sure, my best guess is that it is due to differences in the recording components or filtering algorithms of the two smartphones. When you compare the slow motion audio of shots 4-8, the gunshots in the two recordings definitely sound different.
With the mystery of the 0.080 echo solved, I decided to move on to the 0.170 echo we hear on both the TMZ and Source 4 recordings. I spent a lot of time considering different building walls, the fenceline trees, etc. but I didn’t get any numbers that were close to 0.170. So, I give up. Does anyone have an explanation for this echo timing? If so, I sure would like to know.
Overall Conclusion
Echo analysis of the Source 3 and Source 4 audio is consistent with shots 1-8 being fired by the lone shooter.