The propagation of Kaboom

[Jack Nessan]

This diagram depicts the area of the ground in Dealey Plaza that might be directly affected by the shockwave of a bullet which hits JFK in the head around the Z313 timeframe. It is significantly larger than the affected area of the second shot scenario posted earlier in this thread. And even more witnesses would be directly affected.





The calculated affected area is roughly 108,788 square feet. This is well over 3-times the affected area of the largest of the two areas affected in the two first shot scenarios posted earlier in this thread. The same reasoning as stated in the second shot scenario applies to this scenario as to why I believe this to be a significant possible reason for the first shot to reportedly sound different than the last two shots.

The first shot sounding different can be explained by the position of LHO's rifle. In your modeling you are not taking into account the fact the buildings along Houston Street and next to the TSBD act to reflect sound waves. Dealey Plaza was referred to as an echo chamber. Which is all explained in the HSCA Report.

For what it's worth. Attempting to understand the difference in perception of the shots, I shot a carcano from the living room of an unoccupied farmhouse while a friend stood outside to listen to the difference. Most notable was the large concussion from the shot, with the barrel retracted inside the room, and the fact it blew dust everywhere. Neither of which were experienced with the barrel extended outside the window, which makes perfect sense. Williams, Jarman, and Norman never referred to the first shot as sounding like a firecracker and Williams had dust on his hair. I have never taken the time to figure out where exactly that the phenomenon of a shot sounding like a firecracker started along the street. Garland Slack on Houston referred to the two shots followed by the sound of them striking JFK.

Garland Slack:

11/22

"I was standing there when the President's car passed and just after they rounded the corner from Houston onto Elm Street, I heard a report and I knew at once it was a high-powered rifle shot. I am a [cross-out] big game hunter and am familiar with the sound of hi [sic] powered rifles and I knew when I heard the retort [sic] that the shot had hit something. Within a [cross-out] few seconds I heard another retort [sic] and knew it also had hit something and all I could see was the highly colored hat that Mrs. Kennedy had on."

 12/1:

"He said as the parade passed
the crowds pushed him and he was unable to see the car bearing the
President as it, proceeded west in front of the book store building .
However he said he had been a hunter and had been closely associated
with firearms for many years and he heard two shots in rapid
succession and realized from the sound that they most have been fired
from the interior of a building . He said he did not realize which
building because actually the sound as he first heard it seemed to
come from the direction of the overpass but its particular characteristics
made him feel it had to come from a building instead of from an
open area . "

[Charles Collins]

The first shot sounding different can be explained by the position of LHO's rifle. In your modeling you are not taking into account the fact the buildings along Houston Street and next to the TSBD act to reflect sound waves. Dealey Plaza was referred to as an echo chamber. Which is all explained in the HSCA Report.

For what it's worth. Attempting to understand the difference in perception of the shots, I shot a carcano from the living room of an unoccupied farmhouse while a friend stood outside to listen to the difference. Most notable was the large concussion from the shot, with the barrel retracted inside the room, and the fact it blew dust everywhere. Neither of which were experienced with the barrel extended outside the window, which makes perfect sense. Williams, Jarman, and Norman never referred to the first shot as sounding like a firecracker and Williams had dust on his hair. I have never taken the time to figure out where exactly that the phenomenon of a shot sounding like a firecracker started along the street. Garland Slack on Houston referred to the two shots followed by the sound of them striking JFK.

Garland Slack:

11/22

"I was standing there when the President's car passed and just after they rounded the corner from Houston onto Elm Street, I heard a report and I knew at once it was a high-powered rifle shot. I am a [cross-out] big game hunter and am familiar with the sound of hi [sic] powered rifles and I knew when I heard the retort [sic] that the shot had hit something. Within a [cross-out] few seconds I heard another retort [sic] and knew it also had hit something and all I could see was the highly colored hat that Mrs. Kennedy had on."

 12/1:

"He said as the parade passed
the crowds pushed him and he was unable to see the car bearing the
President as it, proceeded west in front of the book store building .
However he said he had been a hunter and had been closely associated
with firearms for many years and he heard two shots in rapid
succession and realized from the sound that they most have been fired
from the interior of a building . He said he did not realize which
building because actually the sound as he first heard it seemed to
come from the direction of the overpass but its particular characteristics
made him feel it had to come from a building instead of from an
open area . "

Thanks, those are good points. I have considered them. And I stated that these diagrams are a simplified visual aid to try to explain just the shockwave aspect. I did say that I think that the shockwave propagation might have been a major factor. And I do realize that the shockwave doesn’t account for the entire differences or even is applicable to some of the witness accounts.

I would be interested in actually measuring some sound pressure levels and record the sound, preferably at various locations in Dealey Plaza with the rifle in various positions relative to the window. But something like your experience at the abandoned farmhouse would be interesting also. Did y’all make any measurements, or just have the subjective opinions? Do you still have access to the Carcano and ammunition for it? Did the HSCA acoustics investigation report anything like this? I remember reading something about the sound possibly being muffled to some unspecified extent if the rifle was inside the building. But nothing specific.

As far as the reflections of the shockwave goes, I intentionally stated that the outlined area is where the witnesses should be directly affected by the shockwave. Echoes are not part of the direct path of the shockwave from the path of the bullet to the witnesses. Just one of several reasons why they were not a part of this simplified explanation. But frankly, most of the reflective surfaces appear to me to be at angles that wouldn’t reflect the shockwave directly back towards most of the witnesses anyway. However, that doesn’t mean that I don’t believe that the echoes were a factor.