Understanding and Appreciating the HSCA Acoustical Evidence

[Michael Griffith]

Here are some of the other points of evidence that support the HSCA’s acoustical findings:

-- We know that the gunfire impulse patterns on the tape were caused by supersonic gunfire because in each pattern the shock wave (N-wave) arrives before the bullet’s sound wave arrives (2 HSCA 20-22). If the gunfire had been subsonic, there would be no N-wave (2 HSCA 21).

-- The gunshot impulses appear at the correct point in time on the 234 feet of the printed digitized waveforms from the 5.5-minute open-mike segment on the tape (2 HSCA 27-35). The motorcycle microphone became stuck at about 12:28, about two minutes before the assassination, so the suspect impulses, to even qualify as potential gunshots, should begin about 130 seconds into the segment, and they do.  

The gunshot waveforms constituted about 10 feet of the 234 feet of waveform printouts.

-- Moreover, the BBN scientists recognized that the impulses that were later determined to be gunfire were “very unlike” the other impulses up to that point on the waveform printouts:

          After examining the 234 feet of filtered waveforms we discovered there were no other impulsive events on the tape that had been masked by the motorcycle noise, with one exception. That impulsive series of events . . . was very unlike the series of impulsive events that we see before us here [referring to the printouts], at times around 130 seconds after the stuck button. (2 HSCA 31) 

In fact, those patterns were the only patterns of their kind on the tape (2 HSCA 30-36; 8 HSCA 75). 

-- The BBN scientists knew that if these impulse patterns represented gunfire, they must occur for at least 5-10 seconds, since the shooting sequence was at least 5 seconds long. Needless to say, they found that the gunfire impulse patterns occur in a period of 7.9 seconds (8.3 seconds when the tape recorder’s running speed is factored in) (2 HSCA 36-39; 8 HSCA 75). 

My, my, what a “coincidence.” 

-- The BBN scientists detected a drop in the engine noise, starting at around 132-133 on the tape, and that this was the same time that the timing-movement data from the impulse patterns indicated that the motorcycle would have been slowing down to make the sharp 120-degree turn from Houston Street onto Elm Street (8 HSCA 63, p. 23 in the BBN report). 

If that is a coincidence, it is one humdinger of a coincidence. 

-- The muzzle-blast waveforms of the field-test shots were similar to the muzzle-blast waveforms of the police tape’s gunshot impulses, even when a recording of the field-test shots was fed through a radio system similar to the Dallas police radio system (8 HSCA 77). 

Given the known precise nature of muzzle-blast waveforms, this is a remarkable finding. 

-- When the BBN scientists first identified four matches between impulse patterns on the tape and impulse patterns from the Dallas field test, they did not presume that the motorcycle was moving at the speed of the motorcade: 

         Dr. BARGER. We presumed nothing about the location of the motorcycle or its speed or even direction of motion. The matches were made without any presumption whatsoever about the position of the motorcycle, in fact, of course, without any knowledge that the motorcycle was even there. (2 HSCA 70) 

In other words, there was no hint of confirmation bias. In fact, Barger’s team was not even given the position of the motorcycle until after they had completed their detection experiment (2 HSCA 92). 

-- Amplitude analysis of the sounds on the police tape found that when those sounds were originally picked up by the microphone, they were loud enough to have been caused by gunfire before they were compressed by the radio system’s AGC circuitry (8 HSCA 78). 

-- Critics of the acoustics evidence have exaggerated the problem of false alarms, taking one or two statements by Barger markedly out of context. Barger and the other BBN scientists noted that even with a detection threshold of 0.6, there were fewer than 3.3 false alarms out of 432 echo patterns in a 1-second segment (8 HSCA 95-96, pp. 55-56 in the BBN report). 

Finally, this would be a good place to quote the BBN scientists’ explanation of the nature and significance of the timing-movement correlations between the police tape’s impulses and the test-firing impulses: 

          Even a brief glance at Fig. 22 shows that the microphone locations that correspond to correlations at the three times after the first impulse tend to progress uniformly forward along the motorcade route. This conclusion can be quantified statistically by the chi-square test. If the motorcycle were not moving through Dealey Plaza at the time of the assassination, the distance along the motorcade route would be a meaningless coordinate, and the microphone locations for the correlations that exceed the detection threshold would occur at random. When the chart in Fig. 22 is partitioned into a 2 x 2 table by separating time at 5 sec and distance at 250 ft, we find 1, 6, 8, and 0 correlations in the four sections reading from left to right, top to bottom. But the expected number of correlations to be found in these four sections, if the correlations occurred at random, are 4.2, 2.8, 4.8, 3.2. The value of chi-square for the observed and expected values is equal to 11.4. There is only 1 degree of freedom in this 2 x 2 table, and the probability that this large value of chi-square could occur at random is less than 1%. Therefore, there is little doubt that the distance coordinate is meaningful, and we conclude that the motorcycle was moving through Dealey Plaza and did, in fact, detect the sounds of gunfire. (8 HSCA 104, p. 64 in the BBN report) 

No wonder U.S. Naval War College historian Dr. David Kaiser says that these correlations must be explained before the acoustical evidence can be dismissed: 

          And [Don] Thomas was right to raise another point. The odds against Barger and his colleagues having identified a unique set of impulses on the channel 1 tape which just happened, by chance, to match the recordings of actual test shots in Dealey Plaza recorded along an array of microphones seem enormous. That probability in turn has to be multiplied against the chance that the time sequencing of the impulses would match quite closely with the timing of the three or four shots found by the separate panel that analyzed the panning error in the Zapruder film. Until someone can show that there was no basis for Barger’s original conclusions, the issue of whether channel 1 actually recorded a shot from the grassy knoll will, in my opinion, remain open. (The Road to Dallas, pp. 386-387) 

 

Edited July 1, 2023 by Michael Griffith

[Pat Speer]

5 hours ago, Michael Griffith said:

Well, this is another case where I just do not see what you say you see in photographic evidence, just as I do not see what you claim to see in the autopsy photos and x-rays and in Baden's demonstration regarding the clothing holes, to name a few examples. And in this case, we are not just talking about seeing this or that but about subjective judgments about how far X could have moved in Y time, about whether Photo A corresponds with Frame B in this or that footage, etc., etc.

More important, I would note that your article does not even mention, much less try to explain, the powerful evidentiary correlations that show that the tape contains gunfire recorded in Dealey Plaza:

The N-waves, the muzzle blasts, the muzzle-last echoes, and the fact that they occur at the right time and in the right order and interval; the windshield-distortion patterns, and the fact that they occur only when they could have occurred; the remarkable timing-movement correlations between the tape's gunshot impulses and the gunshot impulses from the Dallas test firing, which even the skeptical David Kaiser finds impressive and impossible to dismiss; and the fact that the tape's gunshot echo patterns match the echo-pattern fingerprint of Dealey Plaza. (Other evidence could also be cited.)

These correlations cannot be waved aside just because the incomplete photographic record does not enable us to identify the motorcycle with certainty. Simply put, critics of the acoustical evidence must answer this fundamental question: If the N-waves, muzzle blasts, muzzle-blast echoes, windshield distortions, and Dealey Plaza echo patterns on the tape were not recorded in Dealey Plaza during the assassination, how did they get on the tape?

Dismissing these correlations on the basis of an incomplete photographic record is not terribly far from being as untenable as saying that JFK could not have been shot in Dealey Plaza because no photo shows a gunman firing at JFK in the plaza, because the evidence strongly indicates that Oswald was eating lunch and getting a soda from 12:15-12:30, because no one saw a gunman firing from the grassy knoll or from any other spot in the plaza, and because the witnesses disagreed so markedly about the number and direction of the gunshot sounds that they may have merely been hearing motorcycle backfires.

Oh my. It's not subjective. We know within a few feet where Wiegman was when Thomas' first shot was fired. We also know that McLain is captured in the Bond photo, a second or so after passing Wiegman. If McLain was where the acoustics faithful place him at the time of the first shot--well ahead of Wiegman--it necessitates Wiegman's passing McLain within seconds of the shooting. Thomas as much as admits this on his map, in which he shows what he interprets to be the movements of McLain, and has him traveling less than 5 mph after the shots were fired.  

So...do you honestly believe Dave Wiegman, carrying a heavy TV camera, ran past H.B. McLain, who was riding on a motorcycle? And, if not, can you explain how Wiegman is busy filming the end of his film on the knoll as McLain rides by in the Bond photo? 

[Michael Griffith]

11 hours ago, Pat Speer said:

Oh my. It's not subjective. We know within a few feet where Wiegman was when Thomas' first shot was fired. We also know that McLain is captured in the Bond photo, a second or so after passing Wiegman. If McLain was where the acoustics faithful place him at the time of the first shot--well ahead of Wiegman--it necessitates Wiegman's passing McLain within seconds of the shooting. Thomas as much as admits this on his map, in which he shows what he interprets to be the movements of McLain, and has him traveling less than 5 mph after the shots were fired.  

So...do you honestly believe Dave Wiegman, carrying a heavy TV camera, ran past H.B. McLain, who was riding on a motorcycle? And, if not, can you explain how Wiegman is busy filming the end of his film on the knoll as McLain rides by in the Bond photo? 

One, you are misrepresenting Thomas's arguments, and ignoring many others. Much of the debate over McClain's position most certainly is subjective, and it is downright nonsensical to claim otherwise. You know there is no continuous photographic record of McClain's movements from the time he turned onto Houston Street and then onto Elm Street until the time he left the plaza. The fact that McClain lied so brazenly about his actions after he recanted his initial testimony should serve as bright red flag for skeptics of the acoustical evidence.

We should remember that before he knew what he was supposed to say, McClain freely acknowledged, under oath, that he was the officer the HSCA had identified in the photos of the motorcade on Main and Houston Streets and that he would have been in the approximate position of the open microphone indicated by the acoustical analysis. He said that. 

Two, AGAIN, if the police tape was not recorded in Dealey Plaza during the assassination, how do you explain all the correlations between the tape's gunshot impulse patterns and the field-test gunshot impulse patterns? How did those impulse patterns get on the tape?

You keep trying to prove that no one could have assembled the bicycle, and I keep trying to get you to explain why we have the assembled bicycle if no one could have assembled it. Rather than explain the existence of the assembled bicycle, you keep arguing that no one could have assembled it.

Does it not give you pause that the NRC panel, as determined as they were to refute the acoustical evidence, did not even attempt to explain the windshield-distortion correlations, that their only answer to the presence of the N-waves and muzzle blasts was to claim that Decker's "hold everything" crosstalk proved those sounds were recorded 1 minute after the assassination (wow, so why were there no reports of a shooting involving several rifle shots elsewhere in Dallas that day?), and that they admitted (obliquely and without comment) that their own calculations showed there was only a 7% chance that the timing-movement correlations were a coincidence?

Edited June 30, 2023 by Michael Griffith

[Allen Lowe]

2 hours ago, Michael Griffith said:

One, you are misrepresenting Thomas's arguments, and ignoring many others. Much of the debate over McClain's position most certainly is subjective, and it is downright nonsensical to claim otherwise. You know there is no continuous photographic record of McClain's movements from the time he turned onto Houston Street and then onto Elm Street until the time he left the plaza. The fact that McClain lied so brazenly about his actions after he recanted his initial testimony should serve as bright red flag for skeptics of the acoustical evidence.

Two, AGAIN, if the police tape was not recorded in Dealey Plaza during the assassination, how do you explain all the correlations between the tape's gunshot impulse patterns and the field-test gunshot impulse patterns? How did those impulse patterns get on the tape?

You keep trying to prove that no one could have assembled the bicycle, and I keep trying to get you to explain why we have the assembled bicycle if no one could have assembled it. Rather than explain the existence of the assembled bicycle, you keep arguing that no one could have assembled it.

Does it not give you pause that the NRC panel, as determined as they were to refute the acoustical evidence, did not even attempt to explain the windshield-distortion correlations and admitted (albeit obliquely and without comment) that their own calculations showed that there was only a 7% chance that the timing-movement correlations were a coincidence?

thanks for all this, Mike, it is very convincing.   I do ask, re your earlier comment, what you regard as evidence that Zapruder was edited? I don't disagree with you, I am agnostic on this (and it makes more sense than the kind of alteration that others have alleged), but can you explain? Thanks.

Edited June 30, 2023 by Allen Lowe

[Michael Griffith]

35 minutes ago, Allen Lowe said:

thanks for all this, Mike, it is very convincing.   I do ask, re your earlier comment, what you regard as evidence that Zapruder was edited? I don't disagree with you, I am agnostic on this (and it makes more sense than the kind of alteration that others have alleged), but can you explain? Thanks.

Thanks, Allen. Here is a link to my article "Evidence of Alteration in the Zapruder Film": 

Evidence of Alteration in the Zapruder Film (maryferrell.org)

For a more technical and extensive look at the evidence of alteration, I recommend that you read Doug Horne and Dr. David Mantik research on this subject. Here is one of Horne's articles:

The Two NPIC Zapruder Film Events: Signposts Pointing to the Film’s Alteration – Assassination of JFK

[W. Tracy Parnell]

For those wishing to dive deeper into the subject:

The HSCA Acoustics Issue ~ W. Tracy Parnell (wtracyparnell.blogspot.com)

[Michael Griffith]

6 hours ago, W. Tracy Parnell said:

For those wishing to dive deeper into the subject:

The HSCA Acoustics Issue ~ W. Tracy Parnell (wtracyparnell.blogspot.com)

I'm guessing you did not bother to read the previous posts in this thread before posting your reply. Just a guess.

Anyway, your article does not "diver deeper" into the HSCA acoustical analysis; rather, it recommends articles that ignore most of the evidence that supports the analysis and instead focus on trying to prove that the impulse patterns were not recorded in Dealey Plaza during the assassination. The fact that you claim that John McAdams "effectively explains the issues" suggest you have only read one side of the story, among other things.

If we really want to dive more deeply into the acoustical evidence, let us consider in more depth the intricate nature of the N-waves, muzzle blasts, and muzzle-blast echoes that occur within the identified gunshot impulse patterns on the police tape.

For a sound wave to be an N-wave, it must come before the muzzle blast, and it must do so in the very small and specific timeframe of 10-30 milliseconds, and then the muzzle blast will come after the N-wave, and then the muzzle blast will be followed by its own echo. The Weiss and Aschkenasy report explains how these groups of impulses appear in the graphical representation of one of the test-firing shots:

          The first waveform appearing in the graph, the large peak at the left-hand side, corresponds to the supersonic shockwave [N-wave] of the rifle bullet. The second large peak is the waveform of the muzzle blast. Following it, with generally diminishing heights, are the waveforms of the echoes of the muzzle blast. The delay time of each echo was determined by direct measurement of the distance from the leading edge of the muzzle blast waveform to that of the echo. (8 HSCA 24)

The grassy knoll impulse pattern contains waveforms that conform to these intricate characteristics. 

A loud human yell or a burst of static can cause an impulse pattern that will generally resemble the graphical representation of an N-wave on a spectrogram or oscillogram. However, that yell or static is not going to show the N-wave coming ahead of the muzzle blast and doing so at the correct interval, and it is not going to show the muzzle-blast echo coming after the muzzle blast. Professor Aschkenasy discussed this matter in his HSCA testimony. Weiss and Aschkenasy were displaying an oscillogram, and Congressman Edgar thought that a certain set of "squiggly lines" were caused by supersonic gunfire. Professor Aschkenasy explained the congressman's misunderstanding and explained that identifying an N-wave required a more detailed analysis:

          Mr. EDGAR. How do you know that the squiggly lines you are looking at are really supersonic?

          Mr. ASCHKENASY. They are not supersonic. Those are sound waves. Those are presentations of sound waves. The question, what you might want to ask, is about whether we can tell a bullet was there, namely, was it creating a supersonic shock wave? That is what you are questioning. And those are not supersonic sound waves. Those are sound waves as recorded by a microphone, and put into electrical form by the equipment that was used to transmit it and record it, and there is nothing supersonic in those squiggles that we have up there on that board.

          Mr. EDGAR. Would you answer the question I wanted to ask?

          Mr. ASCHKENASY. Well, because you have a bullet that travels faster than sound, it will get to someplace faster than the sound reaching that same point. We are talking about two components, the bullet and the muzzle blast. 

          The bullet flies, let's just pick a number, at 2,220 feet per second, so that it travels at twice the speed of sound for this particular example, when you fire the gun. And it flies, let's say for 200 feet. It will get at the target 200 feet away in a certain period of time. Just like a boat pushes the water ahead of it creating the V-shape wake behind the boat, that is similar to what you see in a shock wave from a bullet. And that shock wave is what is recorded by the microphone that is right next to the target. 

          Sometime later, finally the sound catches up to it and gets to the target, and the muzzle blast is recorded. That interval of time is fixed, by the fact that you have a certain muzzle velocity and you have a certain distance, they occur in a fixed time relationship. 

          We have also the first, it's covered by the photograph--could somebody remove that photograph, please. If I may point something out there.

          Mr. EDGAR. Yes.

          Mr. ASCHKENASY. I can point out here also these first impulses before the muzzle blast, those are the shock waves, and if you look carefully--I am sure you cannot look that carefully at that distance--but if you look at these graphs, because these microphones are located at different positions on the street, the relationship between the shock wave and the muzzle blast changes, and it changes in a predictable manner because the manner in which you expect them to change is related to where the observer, or the microphone is picking up both the shock waves and the muzzle blast.[/i]

          Now, you measure here about on the average of about 14 milliseconds, 14 thousandths of a second delay between the shock wave and the muzzle blast. We go now here to the police tape and the measurement that we found was around 24 milliseconds here. It is now reasonable to assume because of the measured time interval that the impulse may have attributes of a shock wave.

          If you expand the experiment tape and take an even better look at it, you find there is a little shock wave echo right in between the shock wave and the muzzle blast, and if you expand the police tape properly, you find similar patterns, implying to us that this impulse has the qualities, attributes of a shock wave. (5 HSCA 609-610)

You might ask yourself this question: Why do you suppose the NRC panel declined to offer any explanation for the similarities between the N-wave, muzzle-blast, and muzzle-blast-echo patterns seen in the field-test gunshot impulses and those found in the identified gunshot impulses on the dictabelt? 

Finally, I would note that at least the NRC panel did not make the mistake of making the ludicrous claim that N-waves are "scattered throughout" the police tape or that human speech can cause N-waves, as some WC apologists have suggested.

 

Edited June 30, 2023 by Michael Griffith

[Pat Speer]

6 hours ago, Michael Griffith said:

One, you are misrepresenting Thomas's arguments, and ignoring many others. Much of the debate over McClain's position most certainly is subjective, and it is downright nonsensical to claim otherwise. You know there is no continuous photographic record of McClain's movements from the time he turned onto Houston Street and then onto Elm Street until the time he left the plaza. The fact that McClain lied so brazenly about his actions after he recanted his initial testimony should serve as bright red flag for skeptics of the acoustical evidence.

We should remember that before he knew what he was supposed to say, McClain freely acknowledged, under oath, that he was the officer the HSCA had identified in the photos of the motorcade on Main and Houston Streets and that he would have been in the approximate position of the open microphone indicated by the acoustical analysis. He said that. 

Two, AGAIN, if the police tape was not recorded in Dealey Plaza during the assassination, how do you explain all the correlations between the tape's gunshot impulse patterns and the field-test gunshot impulse patterns? How did those impulse patterns get on the tape?

You keep trying to prove that no one could have assembled the bicycle, and I keep trying to get you to explain why we have the assembled bicycle if no one could have assembled it. Rather than explain the existence of the assembled bicycle, you keep arguing that no one could have assembled it.

Does it not give you pause that the NRC panel, as determined as they were to refute the acoustical evidence, did not even attempt to explain the windshield-distortion correlations, that their only answer to the presence of the N-waves and muzzle blasts was to claim that Decker's "hold everything" crosstalk proved those sounds were recorded 1 minute after the assassination (wow, so why were there no reports of a shooting involving several rifle shots elsewhere in Dallas that day?), and that they admitted (obliquely and without comment) that their own calculations showed there was only a 7% chance that the timing-movement correlations were a coincidence?

Come on, Michael. Thomas admits it's McLain in Bond. And he recognizes that for McLain to be in Bond, he could not have been traveling at the speed the HSCA acoustics experts assumed he was. So he stands by their conclusions of the motorcycle's speed during the shot sequence and proposes that he slowed down dramatically just after. By doing so, it makes Wiegman's presence on the knoll seem possible. But it's nonsense. Here, see for yourself. Here's his exhibit showing McLain's movements across the plaza. Note that the triangles represent his location at each second. Note that he has him turn the corner without slowing, and then slow down dramatically and putt-putt across the plaza after the shooting. Note also that this should have put him right in front of Wiegman in the early frames of his film, but that he is nowhere to be seen in that film. (Because he wasn't there.)

 

[Michael Griffith]

17 minutes ago, Pat Speer said:

Come on, Michael. Thomas admits it's McLain in Bond. And he recognizes that for McLain to be in Bond, he could not have been traveling at the speed the HSCA acoustics experts assumed he was. So he stands by their conclusions of the motorcycle's speed during the shot sequence and proposes that he slowed down dramatically just after. By doing so, it makes Wiegman's presence on the knoll seem possible. But it's nonsense. Here, see for yourself. Here's his exhibit showing McLain's movements across the plaza. Note that the triangles represent his location at each second. Note that he has him turn the corner without slowing, and then slow down dramatically and putt-putt across the plaza after the shooting. Note also that this should have put him right in front of Wiegman in the early frames of his film, but that he is nowhere to be seen in that film. (Because he wasn't there.)

"Come on"? You need to go back and re-read Thomas's research. Thomas argues that McClain could have been in position to record the sounds. And I notice that you skipped over the fact that before McClain knew what he was supposed to say, he freely admitted, under oath, that his bike would have been in position to record the sounds on the tape. 

But, hey, as I've said, for the sake of argument, let us assume that you are right about McClain's position. Fine. Now, tell me how windshield-distortion patterns, N-wave patterns, muzzle-blast patterns, muzzle-blast echo patterns, and echo patterns that match Dealey Plaza's echo fingerprint got on the tape. How did those impulse patterns get on the tape? 

Yes, I fully comprehend that you are saying that the person we thought could have assembled the bicycle could not have assembled it. Fine. So, tell me why or how we have an assembled bicycle in front of us. Did the bicycle assemble itself? Did a tornado blow apart a bicycle parts warehouse and cause some of the parts to assemble into a functioning bicycle?

Edited June 30, 2023 by Michael Griffith

[Pat Speer]

2 hours ago, Michael Griffith said:

"Come on"? You need to go back and re-read Thomas's research. Thomas argues that McClain could have been in position to record the sounds. And I notice that you skipped over the fact that before McClain knew what he was supposed to say, he freely admitted, under oath, that his bike would have been in position to record the sounds on the tape. 

But, hey, as I've said, for the sake of argument, let us assume that you are right about McClain's position. Fine. Now, tell me how windshield-distortion patterns, N-wave patterns, muzzle-blast patterns, muzzle-blast echo patterns, and echo patterns that match Dealey Plaza's echo fingerprint got on the tape. How did those impulse patterns get on the tape? 

Yes, I fully comprehend that you are saying that the person we thought could have assembled the bicycle could not have assembled it. Fine. So, tell me why or how we have an assembled bicycle in front of us. Did the bicycle assemble itself? Did a tornado blow apart a bicycle parts warehouse and cause some of the parts to assemble into a functioning bicycle?

Of course, I've read Thomas' articles. Have you read (and understood) my article, where I went through all his musings about McLain's location, and showed that they were nonsense? I mean, I've met Thomas. I like him just fine. And I love Tink. But they are just wrong about this. As far as the specifics of how impulses are recorded etc, I was surprisingly impressed with Mantik's presentation at one of Gary's conferences. I don't remember the specifics but I remember that he found several instances where square pegs were cut to fit into round holes. As I recall, the impulses on the tape did not fit the shot sequence, so they made what they claimed was a reasonable adjustment, etc. In short, David Mantik--someone with whom I frequently disagree--made what was to me a compelling argument that the impulses on the tape were not related to the shooting and that the acoustics evidence was polluted by confirmation bias. Ironic as heck, I know. 

[Michael Griffith]

3 hours ago, Pat Speer said:

Of course, I've read Thomas' articles. Have you read (and understood) my article, where I went through all his musings about McLain's location, and showed that they were nonsense? I mean, I've met Thomas. I like him just fine. And I love Tink. But they are just wrong about this. As far as the specifics of how impulses are recorded etc, I was surprisingly impressed with Mantik's presentation at one of Gary's conferences. I don't remember the specifics but I remember that he found several instances where square pegs were cut to fit into round holes. As I recall, the impulses on the tape did not fit the shot sequence, so they made what they claimed was a reasonable adjustment, etc. In short, David Mantik--someone with whom I frequently disagree--made what was to me a compelling argument that the impulses on the tape were not related to the shooting and that the acoustics evidence was polluted by confirmation bias. Ironic as heck, I know. 

I already addressed the fact that Mantik argues that the tape impulses do not fit the shot sequence. That is a weak argument, and a rather surprising one, since Mantik knows that the Zapruder film has been altered and thus should know that any success or failure to match the shot impulses with the shot sequence proves little or nothing either way. This is not to mention the fact that the police tape cannot be said to contain all the shots that were fired in the plaza, given the limitations of the police radio system and the fact that the HSCA field test only fired from two locations.

Have you read Mantik's critiques of the acoustical evidence? He does not attempt to explain the windshield-distortion correlations. He does not explain the N-waves, muzzle blasts, and muzzle-blast echoes and their occurrence in the right order and interval. He relies on the badly flawed research of the Sonalysts analysts and Michael O'Dell.

Go talk to RFK assassination researchers about O'Dell's bogus acoustical research in that case regarding the audio of the RFK shooting. Do you know what O'Dell's explanation for the grassy-knoll impulse patterns is? Human speech. That is a bogus argument that was debunked by the HSCA scientists. Even the NRC panel knew better than to float such an unscientific argument.

Mantik is simply out of his field on the acoustical evidence, and unfortunately it shows in his critiques of the acoustics. When I asked him about the correlations that I have discussed in this thread, he said they were remarkable coincidences, which is what he says in his critique of the acoustical evidence in his review of Thompson's Last Second in Dallas.

I am not happy to have to point out these things. I respect Dr. Mantik as much as anybody else does in the research community. He and I have discussed the JFK case off and on since the 1990s. His work on the autopsy materials, especially on the skull x-rays, has been historic and game changing. But he is out of his field on and wrong about the acoustical evidence.

Edited June 30, 2023 by Michael Griffith

[Michael Griffith]

Here are more facts that must be explained by anyone who rejects the HSCA acoustical evidence, and that help us understand and appreciate the nature of that evidence:

-- Acoustical experts Dr. Mark Weiss and Ernest Aschkenasy explained why the muzzle-blast echoes were the most effective and reliable criterion for determining if the third impulse pattern on the police tape was caused by a shot from the grassy knoll. As they noted, muzzle blasts and their echoes come in a certain order and interval, and the echoes can be traced back to the structures off which they are reflected and refracted (8 HSCA 6-9, 16-25).

-- Weiss and Aschkenasy also explained that the pattern of sounds a listener—in this case, a microphone--will hear will be complex and unique for any given pair of gun and microphone locations. This pattern of sounds constitutes an acoustical “fingerprint.” Moreover, if the listener, i.e., the microphone, is in motion when the muzzle blast and the resulting echo sounds reach it, the times at which it will hear the muzzle blast and its echoes will be related uniquely to the microphone’s location when it hears each sound, since echo-delay times can be measured precisely by producing a graph of their waveforms, known as an oscillogram or an oscillograph:

          To answer the basic question, "Was the third group of recorded sounds generated by a gunshot from the grassy knoll?" with a high level of certainty, these sounds needed to be examined for some characteristic that they would have had if they had been generated by such a gunshot, and would not be likely to have had if they had not been. Of the several characteristics that can be used, the most effective and most reliable one is the sequence of delay times of the muzzle-blast echoes. 

          The firing of a gun generates a very loud, very brief explosive blast at the muzzle of the gun. This sound, which typically lasts about five one-thousandths of a second (0.005 seconds, or 5 milliseconds), spreads out in all directions from the gun. If the muzzle blast strikes a wall of a structure, it will be reflected from the surface and will move away from it in a new direction. If the muzzle blast strikes the corner of a structure, it will be diffracted, that is, it will spread out from the corner in many directions. These reflected and diffracted sounds are the echoes of the muzzle blast. Like the muzzle blast, which they closely resemble, the individual echoes are very short in duration. The strengths of the echoes tend to diminish with time, the earliest ones being very loud and the later ones growing progressively weaker as they arrive from increasingly distant locations.

          The time taken for the muzzle blast to be heard at some location depends solely on how fast the sound travels and how far the listener is from the gun. For example, at 65°F the speed of sound is 1123 ft/sec. A listener 112.3 feet away from a gun would hear its muzzle blast 0.1 second after the gun was fired. The time taken for the muzzle blast echoes to be heard also depends on the speed of sound and on the total distance each echo must travel, which is the total of the distance from the gun to the echo-producing object and then to the listener. Since the distance traveled by the muzzle blast to a listener must be less than the distance traveled by one of its echoes, the bang of the muzzle blast is always heard first. Then the echoes that are produced by the muzzle blast bouncing off the corners and surfaces of structures are heard. 

          If we now assume that the sound source (the gun) and the listener are located in a typical urban environment, with a number of randomly spaced echo-producing structures, it is possible to see that the pattern of sounds a listener will hear will be complex and unique for any given pair of gun and listener locations. 

          For example, assuming a fixed location of a listener, the echoes that he hears and the times at which he hears them will be related uniquely to the location of the gun, since for each different location of the gun, even though the distances from the listener to the various echo-producing objects are the same, the distances from these objects to each gun location are different. 

          Consequently, the times at which the echoes are heard will be different for each location of the gun. Similarly, assuming a fixed location of the gun, any change in the location of the listener will change the distances between him and the echo-producing structures, and thus the timing of the pattern of sounds he hears. If the listener is in motion as the muzzle blast and the various echo sounds reach him, the times at which he hears the muzzle blast and its echoes will be related uniquely to his location when he hears each sound. 

         The "listener" that we have discussed, of course, could be either a human ear or a microphone. If a microphone receives the sounds and they are subsequently recorded, the recording becomes a picture of the event, not unlike a "fingerprint," that permanently characterizes the original gun and microphone locations. 

          Echo-delay times in such recordings can be measured easily and precisely by producing a graph of their waveforms on an oscillogram, or oscillograph. Such a graph is shown in figure 1. The narrow peaks represent individual sounds of brief duration (that is, impulse-sounds). The heights of the peaks correspond to the loudness of the impulse sounds; the spacing between peaks corresponds to the time that elapses between them. The largest of the impulse peaks is the muzzle blast. The peaks that follow it are its individual echoes. The distance between the peak that is identified as the muzzle blast and each peak that represents an echo is a measure of the delay time of the echo.... 

          It [the oscillograph] provides a picture of the complex, random spacings of the echo-delay times. When the temperature of the air and the locations of the echo-producing objects are known, the graph is uniquely related to a particular pair of gun and microphone locations. This complex picture can be compared to other such graphs. If the random pattern of echo-delay times (the spacings between peaks) matches in any two such graphs, it may be concluded that the sounds and listener locations that produced both graphs were the same. (8 HSCA 6-9) 

-- At 133 seconds after the start of the stuck-microphone transmission, the level of the noise drops by about 6 decibels (about one-fourth of its previous level). The gunshot impulse patterns begin about 5 seconds after the decrease in the level of the continuous noise and last for about 8 seconds (8 HSCA 11) 

Think about the odds that the duration of the gunshot impulse patterns would be correct if they were just randomly generated noises (leaving aside the problems with assuming that random noises can create the precise acoustical patterns of N-waves, muzzle blasts, and muzzle-blast echoes). If their duration were 4 seconds, or 3 seconds, or 12 seconds, or 14 seconds, etc., they would not have passed the second BBN screening test, and we would not be here talking about them. 

-- The match between the grassy knoll impulses on the tape and the grassy knoll impulses from the field test is even more impressive when we consider the reason the field test fired from a point behind the stockade fence on the grassy knoll. Not only was this location the spot indicated by eyewitness and earwitness testimony, but this location provided the shooter with a better view of Elm Street and with more cover than any other spot on the knoll. No other location on the knoll would have provided this degree of visibility and cover: 

          During the acoustic reconstruction experiment that was conducted by BBN in Dealey Plaza on August 20, 1978, shots were fired from behind the wooden stockade fence on the grassy knoll. This location was consistent with available eyewitness and earwitness testimony. It was a reasonable one since it afforded good visibility of Elm Street while providing good cover for the shooter of a gun. At any other location on the grassy knoll either the visibility or the cover would have been substantially poorer. (8 HSCA 10) 

And remember that the initial BBN analysis, which was done before the acoustical data from the field test were available, placed the third impulse pattern in the vicinity of the grassy knoll. By reducing the spacing between the microphones from the BBN distance of 18 feet to 1 foot, Weiss and Aschkenasy were able to identify a small area on the knoll as the source of the shot. They were also able to vastly reduce the detection threshold window, lowering it from the BBN threshold of 6 milliseconds down to 1 millisecond. Now, to be sure, 6 milliseconds is a narrow detection window, but 1 millisecond is 500% narrower. 

-- Weiss and Aschkenasy explained that calculating how long it took for each muzzle-blast echo to travel from the gun to the microphone, and thus to calculate the echo-delay times, was based on fundamental principles of acoustics: 

          Using fundamental principles of acoustics, it was possible to compute the time it would take for the sound of a muzzle blast to travel from a gun at any assumed point on the grassy knoll to a microphone at any assumed point on Elm Street. Knowing where the echo-producing objects were in Dealey Plaza, it was also possible to compute the time it would take for echoes of the muzzle blast to travel from the gun to the microphone. Subtracting the muzzle-blast travel time from the echo travel times yielded the required sequence of echo-delay times. (8 HSCA 18-19) 

-- The intermittent wind blowing in Dealey Plaza during the assassination would have had no meaningful effect on the delay times of the echoes: 

          For a gunshot fired from the grassy knoll and heard on Elm Street, the travel of most echoes is in approximately the same direction as the directly received muzzle blast. Consequently, the effect of wind on the delay times of these echoes is comparatively small, becoming significant only for windspeeds greater than 40 miles per hour. The weather bureau recorded winds in Dallas on November 22, 1963, as ranging only between 13 knots and 17 knots, which is roughly equal to 15 to 20 miles per hour. (8 HSCA 21)

Edited July 2, 2023 by Michael Griffith

[Tom Gram]

22 hours ago, Pat Speer said:

Come on, Michael. Thomas admits it's McLain in Bond. And he recognizes that for McLain to be in Bond, he could not have been traveling at the speed the HSCA acoustics experts assumed he was. So he stands by their conclusions of the motorcycle's speed during the shot sequence and proposes that he slowed down dramatically just after. By doing so, it makes Wiegman's presence on the knoll seem possible. But it's nonsense. Here, see for yourself. Here's his exhibit showing McLain's movements across the plaza. Note that the triangles represent his location at each second. Note that he has him turn the corner without slowing, and then slow down dramatically and putt-putt across the plaza after the shooting. Note also that this should have put him right in front of Wiegman in the early frames of his film, but that he is nowhere to be seen in that film. (Because he wasn't there.)

 

I guess it’s not totally unreasonable to think that McClain might have slammed on the brakes after seeing JFK’s head blown off, everyone freaking out, and a fellow officer stop, jump off his bike and rush towards the GK vs. just ripping at full speed through the plaza. I don’t think there’s any evidence that actually happened, but it’s not a completely outlandish idea, at least. 

[Pat Speer]

4 hours ago, Tom Gram said:

I guess it’s not totally unreasonable to think that McClain might have slammed on the brakes after seeing JFK’s head blown off, everyone freaking out, and a fellow officer stop, jump off his bike and rush towards the GK vs. just ripping at full speed through the plaza. I don’t think there’s any evidence that actually happened, but it’s not a completely outlandish idea, at least. 

The acoustics evidence is purported to reflect that he neither accelerated nor slammed on his brakes for more than 30 seconds after the shooting. The original experts said he maintained a constant speed throughout the shooting and then afterwards, like he was oblivious. This would have put him under the triple overpass at the time he was photographed in the Bond photo. So Thomas tried to correct their error, and claimed instead that he stopped accelerating two seconds before the first shot, maintained a speed of 11 mph as he turned onto Elm, and then slowed to a constant crawl--idling speed--for the next 30 seconds. The problem is that 1) McLain said he did not do this, 2) no one saw him do this, 3) he is not visible in the Wiegman film when Wiegman briefly turns his camera to where Thomas says he was, and 4) the "idling" speed suggested by Thomas is far slower than the actual idling speed for a Harley. 

We've seen this before. Someone puts together a theory that's supposed to answer the big questions. It is then pointed out that this theory has major holes. So someone else comes along and tweaks it a bit. Only this "tweak" is no better and only shows how questionable this theory was from day one. I am speaking of course of the single-bullet theory. But there's also NAA, which CTs claimed would answer the big questions, until Vincent Guinn testified before the HSCA that it supported the SBT. People then began to question his conclusions, and realized he was largely blowing smoke. Well, this then led to a number of articles by Rahn and Sturdivan in which they tried to resurrect Guinn's findings (much as Thomas has now tried to resurrect the findings of the HSCA acoustics experts). In any event, the scientific community eventually dismissed NAA for bullet lead as being unreliable, and sent it into the cornfield along with a lot other questionable science, like bite-mark analysis, and. to a lesser extent, handwriting analysis. 

Now, with the acoustics evidence, we have a tape which 1) has impulses, not shots, 2) has these impulses at a time which appears to have been after the event in question, 3) has these impulses in a pattern that has been corrected to make it fit a presumed scenario, 4) has impulses that are purported to match up perfectly with how shots would be recorded on a motorcycle microphone starting at a certain point while traveling at a specific speed, which fails to align with the known location of any motorcycle.  Now, to add insult to injury, it turns out that the rider of the motorcycle presumed to have been where the recording started insisted 1) he wasn't where he was supposed to have been, 2)  his microphone was not on the channel on which the impulses were recording, and 3) he knew of sounds that should have been recorded should the mic in question have been his mic, that were not, in fact, recorded. And, oh yeah, there's also the photographic evidence--ALL of which present the motorcycle far behind the location where it would need to have been to pick up the impulses as ID'ed by the acoustics experts. 

Now, our familiarity with the SBT tells us that the doctors said they found no passage from the back wound into the body, and that Specter "corrected" this by claiming that the trajectory of the bullet creating this wound led between two bruised strap muscles, and this suggested that it did indeed pass. Specter then stood by this bs for the rest of his life. Never mind that the strap muscles are on the front of the neck, etc. Well, I see a close parallel in the acoustics evidence. The acoustics faithful hit a wall, similar to the doctors' stating they found no entrance to the body. Only their wall was that they failed to find a motorcycle where they thought there ought to be one. So, much as Specter pretended there were some bruises on some back muscles, and continued to pretend this for the rest of his life, the acoustics faithful continue to pretend McLain rode the motorcycle whose microphone picked up the impulses. It's total crap. 

It amazes me, moreover, how the same people claiming the HSCA's pathology panel had a bias, and blew smoke, and the HSCA's trajectory expert had a bias, and blew smoke, and the HSCA's NAA expert had a bias, and blew smoke, refuse to accept the possibility the acoustics experts were also blowing smoke, only in a different direction. 

Edited July 1, 2023 by Pat Speer

[Michael Griffith]

9 hours ago, Pat Speer said:

The acoustics evidence is purported to reflect that he neither accelerated nor slammed on his brakes for more than 30 seconds after the shooting. The original experts said he maintained a constant speed throughout the shooting and then afterwards, like he was oblivious. This would have put him under the triple overpass at the time he was photographed in the Bond photo. So Thomas tried to correct their error, and claimed instead that he stopped accelerating two seconds before the first shot, maintained a speed of 11 mph as he turned onto Elm, and then slowed to a constant crawl--idling speed--for the next 30 seconds. The problem is that 1) McLain said he did not do this, 2) no one saw him do this, 3) he is not visible in the Wiegman film when Wiegman briefly turns his camera to where Thomas says he was, and 4) the "idling" speed suggested by Thomas is far slower than the actual idling speed for a Harley. 

We've seen this before. Someone puts together a theory that's supposed to answer the big questions. It is then pointed out that this theory has major holes. So someone else comes along and tweaks it a bit. Only this "tweak" is no better and only shows how questionable this theory was from day one. I am speaking of course of the single-bullet theory. But there's also NAA, which CTs claimed would answer the big questions, until Vincent Guinn testified before the HSCA that it supported the SBT. People then began to question his conclusions, and realized he was largely blowing smoke. Well, this then led to a number of articles by Rahn and Sturdivan in which they tried to resurrect Guinn's findings (much as Thomas has now tried to resurrect the findings of the HSCA acoustics experts). In any event, the scientific community eventually dismissed NAA for bullet lead as being unreliable, and sent it into the cornfield along with a lot other questionable science, like bite-mark analysis, and. to a lesser extent, handwriting analysis. 

Now, with the acoustics evidence, we have a tape which 1) has impulses, not shots, 2) has these impulses at a time which appears to have been after the event in question, 3) has these impulses in a pattern that has been corrected to make it fit a presumed scenario, 4) has impulses that are purported to match up perfectly with how shots would be recorded on a motorcycle microphone starting at a certain point while traveling at a specific speed, which fails to align with the known location of any motorcycle.  Now, to add insult to injury, it turns out that the rider of the motorcycle presumed to have been where the recording started insisted 1) he wasn't where he was supposed to have been, 2)  his microphone was not on the channel on which the impulses were recording, and 3) he knew of sounds that should have been recorded should the mic in question have been his mic, that were not, in fact, recorded. And, oh yeah, there's also the photographic evidence--ALL of which present the motorcycle far behind the location where it would need to have been to pick up the impulses as ID'ed by the acoustics experts. 

Now, our familiarity with the SBT tells us that the doctors said they found no passage from the back wound into the body, and that Specter "corrected" this by claiming that the trajectory of the bullet creating this wound led between two bruised strap muscles, and this suggested that it did indeed pass. Specter then stood by this bs for the rest of his life. Never mind that the strap muscles are on the front of the neck, etc. Well, I see a close parallel in the acoustics evidence. The acoustics faithful hit a wall, similar to the doctors' stating they found no entrance to the body. Only their wall was that they failed to find a motorcycle where they thought there ought to be one. So, much as Specter pretended there were some bruises on some back muscles, and continued to pretend this for the rest of his life, the acoustics faithful continue to pretend McLain rode the motorcycle whose microphone picked up the impulses. It's total crap. 

It amazes me, moreover, how the same people claiming the HSCA's pathology panel had a bias, and blew smoke, and the HSCA's trajectory expert had a bias, and blew smoke, and the HSCA's NAA expert had a bias, and blew smoke, refuse to accept the possibility the acoustics experts were also blowing smoke, only in a different direction. 

Your comment suggests you have not read the HSCA acoustical materials. There is a huge difference between the HSCA acoustical experts and the other HSCA experts whom you cite. The BBN acoustical scientists were initially skeptical that the police tape contained gunfire. Ditto for Weiss and Aschkenasy. In fact, when Weiss and Aschkenasy first heard the tape, they said they thought someone had to be kidding. The BBN scientists only began to change their minds when they digitized the 5.5-minute open-mic sequence, printed the oscillograph (soundwave graph), and began to analyze the graph. When they analyzed the soundwave graph, they recognized patterns that had N-wave characteristics and knew right away that this finding demanded that they do further testing. 

If you would read the BBN report, the Weiss and Aschkenasy report, and Barger, Weiss, and Aschkenasy's testimony, you would learn that they ran screening tests that were designed to disqualify suspect impulse patterns as much as they were designed to do the opposite. 

If anything, the HSCA acoustics experts can be accused of being too cautious and of understating their case. A prime example of this is the ultra-conservative way that Weiss and Aschkenasy arrived at their 5% probability of chance figure. They made the needlessly conservative assumption that impulses could occur only in the two intervals in which echoes were observed in the field-test grassy knoll shot. This assumption needlessly ignored the fact that if the impulses were not gunfire, they would have been able to occur between those two intervals, adding 190 milliseconds to the timespan for impulses to occur and vastly reducing the probability of chance to far below 5%. 

Weiss and Aschkenasy acknowledged this in their report. The NRC panel, and every critic since then, ignored this key qualification of the 5% figure. 

Weiss and Aschkenasy explained that their “5% or less” calculation assumed that impulses could only occur from 0 to 85 milliseconds and from 275 to 370 milliseconds, because these were the intervals in which echoes occurred in the field-test grassy knoll shot.

The grassy knoll test shot produced a distinctive pattern in which the echoes arrived in two clusters. The first cluster arrived in the first 85 milliseconds and consisted of echoes from structures facing Elm Street. The first cluster was followed by a gap of 190 milliseconds, corresponding to the open space at the intersection. The second echo cluster arrived in the last 95 milliseconds (275 to 370) and originated with the structures on Houston Street. This is why Weiss and Aschkenasy assumed in their analysis that impulses could only occur during the timespan of these two timeframes, and these timeframes added up to 180 milliseconds. 

But, if the dictabelt impulses were not caused by gunfire, if they were generated by random noise, then the timespan during which impulses could have occurred more than doubles: it goes from 180 milliseconds to 370 milliseconds. Why? Because there is a 190-millisecond interval between the two intervals of 0-85 and 275-370 milliseconds. Obviously, if you more than double the timespan for impulses to occur, this vastly reduces the probability that random noise caused the dictabelt grassy knoll shot.

Here is how Weiss and Aschkenasy explained this in their report:

          The high degree of correlation between the impulse [the dictabelt grassy knoll shot] and echo sequences [of the grassy knoll test shot] does not preclude the possibility that the impulses were not the sounds of a gunshot. It is conceivable that a sequence of impulse sounds, derived from non-gunshot sources, was generated with time spacings that, by chance, corresponded within one one-thousandth of a second to those of echoes of a gunshot fired from the grassy knoll. However, the probability of such a chance occurrence is about 5 percent. This calculation represents a highly conservative point of view, since it assumes that impulses can occur only in the two intervals in which echoes were observed to occur, these being the echo-delay range from 0 to 85 milliseconds and the range from 275 to 370 milliseconds.

          However, if the impulses in the DPD recording were not the echoes of a gunshot, they could also have occurred in the 190-millisecond timespan that separated these two intervals. Taking this timespan into account, the probability becomes considerably less than 5 percent that the match between the recorded impulses and the predicted echoes occurred by chance. (8 HSCA 32)

Are you ever going to get around to dealing with the correlations between the police tape's impulse patterns and the field-test impulse patterns? AGAIN, okay, if McClain's motorcycle did not record the sounds on the tape, and if the sounds did not occur in Dealey Plaza and even occurred after the assassination, how did those impulse patterns get on the tape? The tape contains N-waves, muzzle blasts, muzzle-blast echoes, windshield-distortion patterns, and only when the microphone was in position to record them. How did these patterns get on the tape? 

If no one could have assembled the bicycle, tell my how the bicycle got assembled. You can repeat over and over and over again that you do not think anyone could have assembled the bicycle. The problem is that we have an assembled bicycle. Just tell me how you think the bicycle got assembled. 

Edited July 2, 2023 by Michael Griffith