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Author Topic: The HSCA Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination  (Read 7537 times)

Offline Joe Elliott

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Question 1:

In the BBN Exhibit F-367 Table, a portion of which I show here:

TestBeginning Time ofZap.RifleTarget
IDFirst impulse onFrameLocationLocation
Tape Segments (sec)(Thomas)
B137.70176TSBDLocation-z 155
D137.70176TSBDLocation-z 313
E137.70176KNOLLLocation- Tague

Why does it show the impulse pattern at 137.70 as matching the patterns expected by shots from both the TSBD and the Grassy Knoll?


It seems to me, that at least 2 of these matches are by luck. They are flukes. And this is the explanation for 2 of the matches, why not all 3?



How about if you just explain one of the correlations in the acoustical evidence: the windshield-distortion correlations? The HSCA scientists realized that soundwaves passing through a motorcycle windshield would experience distortion. So they ran tests to determine the characteristics of windshield distortion. And, lo and behold, they found that the dictabelt shots that match test shots from the Book Depository all contained windshield distortions but that the dictabelt shot that match test shots from the grassy knoll contain no such distortions. My, my, my!

The common pattern you show, is when you cannot answer my questions, you introduce another argument from left field. So instead of dealing with the contradictions in the BBN’s own data, you bring up “windshield-distortion”.

The shots from the TSBD contain windshield-distortions but those from the grassy knoll do not?

How can anyone say that when the BBN data, for the shots at z176, z205 and z313, match the pattern predicted for both a shot from the TSBD and the grassy knoll?

Question 2:

Did the impulse patterns correspond to z176, z205 and z213 shots, show “windshield-distortions”?




This petty, juvenile, and erroneous comment shows why you are not credible,

You are constantly insulting me with every post you direct to me. I don’t do that to you. You write like a 5-year-old who is constantly having a temper tantrum. I am just asking for clarifications for why the BBN data, the Exhibit F-367 Table, appears to contradict itself so much. And you are not explaining why, either to me or the other readers.

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Offline Michael T. Griffith

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The common pattern you show, is when you cannot answer my questions, you introduce another argument from left field.

No, you ask me ridiculous, diversionary, irrelevant questions, and I attempt to get you to address the real issues, the same issues that the NRC panel and O'Dell and Bowles have never gotten around to addressing: the remarkable, intricate correlations between the dictabelt gunshot impulse patterns and the test-firing impulse patterns.

I have commented on your confusion about F-367 in several replies, including one very long reply where I quoted extensively from Dr. Barger's testimony where he explained F-367. But you keep ignoring what he said and keep demanding that your imagined "contradictions" be "explained."

So instead of dealing with the contradictions in the BBN’s own data,

The "contradictions" are in your mind, or else you know better but are hoping you'll fool others.

you bring up “windshield-distortion”.

Uh, yeah, because windshield distortion is a known factor in acoustical analysis, because we know from science that when soundwaves pass through a windshield, the windshield causes certain distortions in the wave and in the echo pattern. You'd know that if you had bothered to do your homework.

The shots from the TSBD contain windshield-distortions but those from the grassy knoll do not? How can anyone say that when the BBN data, for the shots at z176, z205 and z313, match the pattern predicted for both a shot from the TSBD and the grassy knoll?

How could the HSCA experts say that the TSBD shots contain windshield distortion? Because they ran tests on this to determine the patterns that would be caused by windshield distortion. From the WA report:

Quote
A different but also significant effect on the relative strengths of the recorded echoes would have been caused by the motorcycle windshield. On the DPD motorcycles, the microphone was usually mounted on a bar directly behind the windshield. Sounds arriving from the front of the motorcycle would have diffracted around the windshield and in doing so would have lost strength. As determined by experiment, the windshield of a 1960's Harley Davidson motorcycle attenuated [weakened] gunshot sounds received from in front of the motorcycle by 3 decibels to 6 decibels. The amount of attenuation [weakening, decreasing] depended on how close the microphone was to the windshield. Obviously, sounds received from the sides and rear of the motorcycle would not be affected by the windshield. (8 HSCA 30-31)

Then, when the HSCA scientists did the refined analysis, they found that the TSBD shots all contain windshield distortion but that the grassy knoll shot goes not. Dr. G. Paul Chambers, a renowned physicist who has worked with NASA, the Naval Surface Warfare Center, and the Naval Research Laboratory:

Quote
Weiss and Aschkenasy . . . also took into account muting and distortion of the acoustical signature due to the windshield of the motorcycle. When they considered this in their analysis, they found that the earlier shots determined by BBN to be from the Texas School Book Depository showed this distortion, while the acoustical sequence that matched the test shot from the grassy knoll did not exhibit this effect.

This is precisely the result expected for a microphone mounted on a motorcycle moving in Kennedy’s motorcade along Houston Street facing the Depository, where the sound of the shot from this location would pass through the windshield, but moving sideways to the direction of the grassy knoll so that a shot from this location would not need to pass through the windshield to reach the microphone. This lent further credence to the validity of their analysis. (Chambers, Head Shot: The Science Behind the JFK Assassination, p. 102)

Question 2:

Did the impulse patterns correspond to z176, z205 and z213 shots, show “windshield-distortions”?

This is a silly, disingenuous question. And I see you again put "windshield-distortions" in quotes, as if windshield distortion is not a known, scientifically established phenomenon.

You are constantly insulting me with every post you direct to me. I don’t do that to you. You write like a 5-year-old who is constantly having a temper tantrum.

You repeatedly insult and belittle Dr. Thomas, calling him "a bug guy," "an insect guy," etc., but you get upset when I call you out for making ignorant claims. I am just tired of your dishonesty, your evasion, and your misrepresentation. You have done nothing but duck and dodge and bob and weave every time I have asked you direct, clear questions about the dictabelt-test firing correlations.

I am just asking for clarifications for why the BBN data, the Exhibit F-367 Table, appears to contradict itself so much.

No you're not. You're throwing up a bunch of absurd smoke to avoid dealing with the core of the acoustical evidence. And I'm just not going to waste time playing your games. Again, I have already dealt at length with your misreading/misrepresentation of F-367.

And you are not explaining why, either to me or the other readers.

Oh, I'll let our readers decide whether or not I am "explaining why." Your silly questions are answered by the HSCA materials and in subsequent research. Your questions are based either on a surreal misreading of the HSCA materials or on a deliberate misrepresentation of them.

The HSCA scientists explained in detail how they separated the false alarms/false positives from the final candidate impulses. They explained how they screened every single impulse on the dictabelt tape. They explained how they compared the viable candidate impulse patterns to patterns of test-firing gunshots. They explained how they identified N-waves, muzzle blasts, and muzzle-blast echoes. They explained how they tested for windshield distortion. They explained how they matched the test-firing echo patterns to the gunshot impulse patterns on the dictabelt tape. Etc., etc. etc.

But you don't want to talk about any of that. You keep bringing up ancillary issues based on your misreading/misrepresentation of the HSCA materials, most of which you have not even really read. And you have defiantly announced that you will not read the most authoritative analysis of the acoustical evidence now available, i.e., Dr. Thomas's four chapters on the subject in his book Hear No Evil, even though he wrote them in close consultation with Dr. Barger.
« Last Edit: September 27, 2020, 10:05:42 PM by Michael T. Griffith »

Offline Joe Elliott

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In the BBN Exhibit F-367 Table, a portion of which I show here:

TestBeginning Time ofZap.RifleTarget
IDFirst impulse onFrameLocationLocation
Tape Segments (sec)(Thomas)
B137.70176TSBDLocation-z 155
D137.70176TSBDLocation-z 313
E137.70176KNOLLLocation- Tague

Question 1:

Why do the impulses from three different 1978 test shots, resemble each other so closely, even though the shots are from fired from two different locations, at three different targets separated from each other by over a hundred feet?


So close that the BBN found a correlation with each of these three-test shot with the 1963 Dictabelt impulse of 137.70.


Question 2:

Shouldn’t each test shot, fired from different positions and/or fired at widely separate targets, produce its own unique wave pattern that would not be shared with other test shots?



Question 3:

How can the science of Acoustics be used to reconstruct what happened when a recorded impulse pattern correlation with different firing positions, firing at different targets?


It would seem impossible to say that “this shot was fired from this position, firing at this target”, because of Correlation “A” when Correlation “B” contradicts this.

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Offline Joe Elliott

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********** Warning, this is not the real data, only what good data should look like **********
TestBeginning Time ofZap.RifleTarget
IDFirst impulse onFrameLocationLocation
Tape Segments (sec)(Thomas)
B137.70176TSBDLocation-z 155
G139.27205TSBDLocation-z 224
K140.32224TSBDLocation-z 224
L145.15313KNOLLLocation-z 313
O145.61321TSBDLocation-z 313



********** Here is the data the BBN actually got **********
TestBeginning Time ofZap.RifleTarget
IDFirst impulse onFrameLocationLocation
Tape Segments (sec)(Thomas)
A136.20
B137.70176TSBDLocation-z 155
D137.70176TSBDLocation-z 313
E137.70176KNOLLLocation- Tague
G139.27205TSBDLocation-z 313
I139.27205TSBDLocation-z 313
J139.27205KNOLLLocation-z 313
K140.32224TSBDLocation-z 313
L145.15313KNOLLLocation-z 313
M145.15313TSBDLocation-z 224
N145.15313TSBDLocation-z 313
O145.61321TSBDLocation-z 313
P145.61321TSBDLocation- Tague
Q145.61321TSBDLocation-z 224

Question:

Why didn’t the data the BBN end up looking something like the first table. Where we don’t have contradictory correlations. Like a 1963 Dictabelt impulse pattern matches both a shot from the TSBD and from the Grassy Knoll. Where the shots end up hitting on or at least reasonably near the limousine?

Instead, we end up with a chart that contradicts itself, shows support for the same shot coming from the TSBD and the Grassy Knoll. And as far as “Target Locations” seems to find random correlations, and not correlations where the target location matches the limousine location at that time.

Why is that?




The obvious answer is bad data. And using a correlation coefficient threshold that is too low. Giving us random answers as to the location of the shooter and the location of the target.



The only part of the data is the location of the motorcycle. Well, not that good, because it does not match what is in the Hughes film and the Altgens photograph. But this can be explained by the hypotheses that the BBN only checked for matches where they anticipated where the motorcycle might be. Not all possible combinations but only the ones that seemed plausible. Due to a lack of time. So, if they found the first match 150 feet behind the limousine, they would look for the second 150 feet behind the limousine at the time of the second “shot”. So whatever correlation they discovered, it would match a motorcycle travelling 150 feet behind the limousine at around 11 mph.

Hence, the poor correlation of the location of the shooter, the poor correlation of the location of the target, but the good correlation of the location of the motorcycle. To me, this explanation makes sense.

Offline Michael T. Griffith

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********** Warning, this is not the real data, only what good data should look like **********
TestBeginning Time ofZap.RifleTarget
IDFirst impulse onFrameLocationLocation
Tape Segments (sec)(Thomas)
B137.70176TSBDLocation-z 155
G139.27205TSBDLocation-z 224
K140.32224TSBDLocation-z 224
L145.15313KNOLLLocation-z 313
O145.61321TSBDLocation-z 313

********** Here is the data the BBN actually got **********
TestBeginning Time ofZap.RifleTarget
IDFirst impulse onFrameLocationLocation
Tape Segments (sec)(Thomas)
A136.20
B137.70176TSBDLocation-z 155
D137.70176TSBDLocation-z 313
E137.70176KNOLLLocation- Tague
G139.27205TSBDLocation-z 313
I139.27205TSBDLocation-z 313
J139.27205KNOLLLocation-z 313
K140.32224TSBDLocation-z 313
L145.15313KNOLLLocation-z 313
M145.15313TSBDLocation-z 224
N145.15313TSBDLocation-z 313
O145.61321TSBDLocation-z 313
P145.61321TSBDLocation- Tague
Q145.61321TSBDLocation-z 224

Question:

Why didn’t the data the BBN end up looking something like the first table. Where we don’t have contradictory correlations. Like a 1963 Dictabelt impulse pattern matches both a shot from the TSBD and from the Grassy Knoll. Where the shots end up hitting on or at least reasonably near the limousine?

Instead, we end up with a chart that contradicts itself, shows support for the same shot coming from the TSBD and the Grassy Knoll. And as far as “Target Locations” seems to find random correlations, and not correlations where the target location matches the limousine location at that time.

Why is that?


The obvious answer is bad data. And using a correlation coefficient threshold that is too low. Giving us random answers as to the location of the shooter and the location of the target.

The only part of the data is the location of the motorcycle. Well, not that good, because it does not match what is in the Hughes film and the Altgens photograph. But this can be explained by the hypotheses that the BBN only checked for matches where they anticipated where the motorcycle might be. Not all possible combinations but only the ones that seemed plausible. Due to a lack of time. So, if they found the first match 150 feet behind the limousine, they would look for the second 150 feet behind the limousine at the time of the second “shot”. So whatever correlation they discovered, it would match a motorcycle travelling 150 feet behind the limousine at around 11 mph.

Hence, the poor correlation of the location of the shooter, the poor correlation of the location of the target, but the good correlation of the location of the motorcycle. To me, this explanation makes sense.

This is both comical and pathetic.  These questions are based on a mix of misreading and/or misrepresentation and omission.

Plus, I have already debunked several of the claims in his reply, but Mr. Elliott keeps repeating them anyway: To cite just one example, regarding his claim that "BBN only checked for matches where they anticipated where the motorcycle might be," this is utterly erroneous and is the exact opposite of what they did. It is beyond me how anyone could get on a public board and make such an abjectly false statement when the relevant materials make it clear that the BBN scientists did the exact opposite of what Mr. Elliott claims they did.

Be advised that Mr. Elliott is the same guy who spent weeks claiming that the 4-second impulse pattern was rejected only because it wasn't long enough, who could not tell the difference between Barger's testimony and the BBN report, who did not even understand the basic timeline of the HSCA acoustical analysis (i.e., the preliminary analysis vs. the later analysis done after the test firing), who did not even know when the HSCA said the first shot was fired, among other egregious errors. I don't mention these things to kick a wounded horse, but just to enable readers to understand Mr. Elliott's record of making erroneous statements.

The best way to answer Mr. Elliott's ball of confusion is not to spend numerous paragraphs unpacking his errors and omissions but to provide a clear explanation of the relevant facts. I will do so by quoting from Dr. G. Paul Chambers' chapter on the acoustical evidence in his book Head Shot: The Science Behind the JFK Assassination.

Dr. Chambers is a physicist and an internationally recognized expert in the field of shock physics. He has performed extensive high-speed photographic studies of high-velocity impacts and deformations of solids as well as computer modeling of shock wave and matter interactions. He has worked with NASA at NASA's Goddard Optics Branch. He has worked as a supervisory research physicist at the Energetic Materials and Detonation Science Department of the Naval Surface Warfare Center, and as a research physicist with the Condensed Matter and Radiation Sciences Division of the Naval Research Laboratory. The quote below appears in my article on the acoustical evidence, the same article that Mr. Elliott keeps pretending to be answering:

Quote
The HSCA commissioned the acoustics firm of Bolt, Beranek, & Newman (BBN) to perform a scientific analysis on the Dictabelt recording. This firm had previously successfully utilized acoustical analysis to determine the events that transpired during the Kent State shooting in 1970. Their acoustical analysis was later used as evidence presented to a grand jury to determine which national guardsman had fired first. BBN was also pointed by Judge John J. Sirica to serve on a panel of technical experts to analyze President Richard Nixon’s Watergate tapes.

Led by their chief scientist, Dr. James Barger, BBN converted the sounds on the tapes [the Channel 1 tape and the Channel 2 tape] to digitized waveforms. They then ran the waveforms through electronic filters to eliminate repetitive background noise like the sound of the motorcycle pistons firing. The firm then examined the processed waveforms for “sequences of impulses.” Their analysis indicated that there were six sequences of interest, spaced together within an eleven-second period recorded on channel 1, which could be consistent with the sounds of gunshots. . . .

Weiss and Aschkenasy reviewed Barger’s analysis and conclusions. They found that Barger’s analysis was valid and his conclusions supported by the evidence on the tape. They concurred with his recommendation to conduct live-fire tests in Dealey Plaza to determine the origin and direction of the gunshots, and they approved his plan for acoustical reconstruction. . . .

In Dealey Plaza, the sounds of gunshots would produce similar echoes. When recorded and captured on a specialized electronic device like an oscilloscope that converts sound patterns into pictures, these echoes appear as “acoustical waveforms” and appear as unique signatures of sound-producing events. In the case of a rifle shot in Dealey Plaza, the acoustical signatures would differ based on the origin, direction, and velocity of the shot, as well as the location of the recording microphone. The echo patterns would depend on the timing of sound reflections off building or other structures and obstructions in the plaza. . . .

A recording was made of the sounds received at each microphone during each test shot, making a total of 432 recordings of impulse sequences. . . . Each recorded impulse sequence was then compared with each of the six impulse patterns on the channel 1 Dictabelt recording to see the degree to which significant points in each impulse pattern matched. . . .

The time of the arrival of the impulses, or echoes, in each sequence of impulses was the characteristic being compared, not the shape, amplitude, or any other characteristic of the impulses or sequences. . . .

When the BBN team performed their analysis of the acoustical waveforms, they
found something extraordinary. When they compared the impulse sequences
from the acoustical reconstruction to the sequences on the original Dictabelt
recording, they found a number of significant matches. When the locations of the
microphones that recorded matches in the reconstruction were plotted on a
graph of time versus distance, it was found that the location of the microphones
that recorded matches were clustered around a line on the graph that was
consistent with the known speed of the motorcade (11 mph). . . .

Of the thirty-six microphones placed along the motorcade route, the one that recorded the sequence of impulses that matched the third impulse on the 1963 dispatch tape [the dictabelt tape] was farther along the route than the one that recorded the impulses that matched the second impulse on the dispatch tape. The locations of the microphones were consistent with the distance a motorcycle traveling at about 11 mph would cover in the elapsed time between impulses on the dispatch tape. . . . Applying a statistical formula, Barger estimated that since the microphones clustered around a line representing the speed of the motorcade, there was a 99 percent probability that the Dallas police dispatch tape did, in fact, contain impulses transmitted by a microphone in the motorcade in Dealey Plaza during the assassination. . . .

Weiss and Aschkenasy, specialists in sonar applications . . . examined Dealey Plaza carefully to determine which structures were most likely to have caused the echoes recorded by the microphone in the acoustical reconstruction that had exhibited a match to the shot from the grassy knoll. They verified and refined their identifications of echo-producing structures by examining the results of the 1978 reconstruction [the test firing in Dealey Plaza]. This approach allowed them to look for matches in the data with a 1 ms [millisecond] correlation. . . . Matches at this level of temporal precision substantially reduced the possibility that a
match could occur as a result of random noise.

In Dealey Plaza, echoes from gunshot test patterns arrive in two discrete [different] clusters, differing in time by about 190 ms. Echoes originating from structures along Elm Street arrive within 85 ms, while echoes from structures farther back on Houston Street arrive in the last 95 ms of a typical 370-msduration test pattern. In addition, a “muzzle blast” is usually prominent at the beginning of a gunshot acoustical pattern, while an N-wave (a shock wave traveling faster than the speed of sound due to the rifle bullet exceeding the sound barrier) arrives prior to the muzzle blast. The waveform identified as the grassy knoll shot is shown in figure 13. The presence of an N-wave in this waveform was consistent with the acoustical signature of a supersonic rifle bullet.  . . .

Weiss and Aschkenasy were able to incorporate the movement of the motorcycle in their analytical model. For instance, over the time period of the 370-ms gunshot acoustical pattern recording, the motorcycle would have moved about five feet. Therefore, corrections had to be made to account for a moving microphone during the actual 1963 events. They also took into account muting and distortion of the acoustical signature due to the windshield of the motorcycle. When they considered this in their analysis, they found that the earlier shots determined by BBN to be from the Texas School Book Depository showed this distortion, while the acoustical sequence that matched the test shot from the grassy knoll did not exhibit this effect.

This is precisely the result expected for a microphone mounted on a motorcycle moving in Kennedy’s motorcade along Houston Street facing the Depository, where the sound of the shot from this location would pass through the windshield, but moving sideways to the direction of the grassy knoll so that a shot from this location would not need to pass through the windshield to reach the microphone. This lent further credence to the validity of their analysis. (Chambers 96-102)

Here is my article, the one that Mr. Elliott keeps pretending he's answering:

https://miketgriffith.com/files/hscaacous.pdf

« Last Edit: September 28, 2020, 04:09:15 PM by Michael T. Griffith »

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Offline Joe Elliott

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This is both comical and pathetic.  These questions are based on a mix of misreading and/or misrepresentation and omission.

Plus, I have already debunked several of the claims in his reply, but Mr. Elliott keeps repeating them anyway: To cite just one example, regarding his claim that "BBN only checked for matches where they anticipated where the motorcycle might be," this is utterly erroneous and is the exact opposite of what they did. It is beyond me how anyone could get on a public board and make such an abjectly false statement when the relevant materials make it clear that the BBN scientists did the exact opposite of what Mr. Elliott claims they did.

Be advised that Mr. Elliott is the same guy who spent weeks claiming that the 4-second impulse pattern was rejected only because it wasn't long enough, who could not tell the difference between Barger's testimony and the BBN report, who did not even understand the basic timeline of the HSCA acoustical analysis (i.e., the preliminary analysis vs. the later analysis done after the test firing), who did not even know when the HSCA said the first shot was fired, among other egregious errors. I don't mention these things to kick a wounded horse, but just to enable readers to understand Mr. Elliott's record of making erroneous statements.

The best way to answer Mr. Elliott's ball of confusion is not to spend numerous paragraphs unpacking his errors and omissions but to provide a clear explanation of the relevant facts. I will do so by quoting from Dr. G. Paul Chambers' chapter on the acoustical evidence in his book Head Shot: The Science Behind the JFK Assassination.

Dr. Chambers is a physicist and an internationally recognized expert in the field of shock physics. He has performed extensive high-speed photographic studies of high-velocity impacts and deformations of solids as well as computer modeling of shock wave and matter interactions. He has worked with NASA at NASA's Goddard Optics Branch. He has worked as a supervisory research physicist at the Energetic Materials and Detonation Science Department of the Naval Surface Warfare Center, and as a research physicist with the Condensed Matter and Radiation Sciences Division of the Naval Research Laboratory. The quote below appears in my article on the acoustical evidence, the same article that Mr. Elliott keeps pretending to be answering:

Here is my article, the one that Mr. Elliott keeps pretending he's answering:

https://miketgriffith.com/files/hscaacous.pdf

Mr. Griffith is playing the same trick he often plays. He claims an issue has already been dealt with and provides a link to a long article. And implies that the answer is to be found somewhere in this article.

It would be easy for him to cut and paste the relevant paragraph if, it existed. As an example, I will cut and paste a random paragraph from his article to show how easy this is:


Random Paragraph:

Quote
Led by their chief scientist, Dr. James Barger, BBN converted the sounds on the
tapes [the Channel 1 tape and the Channel 2 tape] to digitized waveforms. They
then ran the waveforms through electronic filters to eliminate repetitive
background noise like the sound of the motorcycle pistons firing. The firm then
examined the processed waveforms for “sequences of impulses.” Their analysis
indicated that there were six sequences of interest, spaced together within an
eleven-second period recorded on channel 1, which could be consistent with the
sounds of gunshots. . . .

So as far as the two claims I have made, he has not really provided any quotes from Mr. Barger that either is false. These claims are:

1.   There are two impulse pattern sequences recorded, just during the 5.5-minute period that the transmission key is stuck. One is 10 seconds long, the other 4. So, it appears the 10-second-long sequence is not unique. Since both were not caused by gunfire, perhaps neither were.
Perhaps if this second sequence was analyzed, they would have found correspondence with some impulse waves from their 1978 tests.
The only quotes I can find from Dr. Barger, about why the 4-second sequence was not investigated further were:
a.   The sequence was too short, since the Zapruder film seemed to show the shooting lasted at least 5 seconds.
b.   He claims it must have been created by someone else trying to transmit over Channel 1. But does not provide any technical reasons why he believes this, like the amplitude of the waves was too large or too small. For all I know, this is speculation on Dr. Barger’s part.

2.   I believe it is likely that BBN did not systematically check all 2,592 combinations of the 432 waveforms, created in the 1978 tests, with the 6 waveforms of interest, recorded on the 1963 Dictabelt. I believe this was not done because of the lack of time, only 10 days to make the measurements and to do the calculations with calculators where all the numbers would have to be manually entered.
Instead, I speculate that after they thought they found one shot, they used this information, combined with the assumption that the motorcycle maintained a roughly 11 mph speed to tell them where to go look for other matches. If this was done, any correlation they found would match the scenario of a motorcycle moving at 11 mph. This would explain why the location of the motorcycle gets consistent results, which is what you want. While still getting random results for the location of the shooter and the area of Elm Street the bullet struck.
Again, this is speculation on my part but reasonable speculation. It provides an explanation as to why the data for the location of the motorcycle is good, while the data for the location of the shooter and where the bullet struck is so bad.
And Mr. Griffith, for all his bluster, has not provided us with a quote from Dr. Barger where he claims they did indeed conduct a systematic check of all possible 2,592 combinations in the time period of 10 days, from when the shooting tests were conducted, to when he called the HSCA to report that they had found 15 correlations.
Now, I can find claims on the internet that Dr. Barger had completed these 2,592 comparisons. But neither I, nor apparently Mr. Griffith, can find a where Dr. Barger claims that all these 2,592 comparisons were actually done.

Again, why should my speculation:
          that the BBN did not conduct a thorough systematic search through all 2,592 combinations, due to a lack of time
be considered more likely than Mr. Griffith’s speculation:
          that that BBN did conduct a thorough systematic search through all 2,592 combination, despite the time pressure

Because my theory explains why the BBN data is so bad at getting results that don’t contradict themselves as to the location of the shooter and where the bullet struck, while giving consistent results on the location of the motorcycle. And Mr. Griffith’s theory, does not.

Offline Joe Elliott

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One aspect of the case that CTers make for the Acoustic evidence, is a strong tendency to emphasis the positive and to skip over the negative, as far as the correlations the BBN found. This is most obvious in the maps of Dealey Plaza to show the information about the acoustic tests.


Below is a typical map used by CTers:

https://www.maryferrell.org/wiki/images/6/60/Pict_essay_acousticshistory_AcousticMap_lrg.jpg

Very prominent are the circles that show the estimate of the motorcycle positions. This is, by far, the most positive aspect of the BBN Data shown in F-367.

They often do not show the location of the “Target”, the area where the bullet struck. Or, if shown, is shown in very small print that is difficult, often impossible, to read. This hides how wildly F-367 is off on these estimates. It appears that right from the beginning, BBN was, at least subconsciously, hiding this flaw. In F-367, under the “Target Location” column, they could have put “z-155”, “z-224”, “z-333” or “Tague” to clearly show where the acoustic evidence indicated where the bullet struck. Instead, they used “Target 1, 2, 3, 4” so it was not as clear how wildly off these estimates were.

The location of the shooter was less easy to conceal. Not referring to the target locations as “TSBD” and “Grassy Knoll” but as “Shooter 1” and “Shooter 2” would have obscured a major point they were trying to make. A shot from the grassy knoll was discovered.


Even the motorcycle positions shown on the map are a little dishonest. They show the locations of the motorcycle, the green circles, based on their evidence, after they tossed out the “false alarms”. But much of the evidence does not match this.

Particularly for the second shot. While a couple of the table entries of F-367 match the second circle, one of them matches the fifth circle, about 110 feet up the road. Another is about 25 feet up the road. That is why I think this second shot was the first one they searched for, giving us a wide stretch of found correlations, before the search focus became so much narrower for the other shots.

Also, the locations for the motorcycle for the fourth shot are not too good. While one of the correlations is in the center of the fourth green circles, the other two are 25 to 30 feet further up the road.

And the location for the fifth motorcycle for the fifth shot are also off. Again, one of the correlations is in the center of the fifth greet circle, but the other two are further up the road, one by 20 feet.

So, while Mr. Griffith, and even I, have spoken of the good correlation of the data with the motorcycle position consistent with the motorcycle trailing behind by 150 feet at 11 mph, this “good correlation” is greatly exaggerated. It is based on the tossing out a lot of correlations that are deemed “false alarms”.

But problems with the motorcycle estimates are difficult to see, because the positions of the microphones are hard to see, particularly for the second array, 2 ( 1 ) through 2 ( 12 ).


So, there are clear signs of the BBN and its supporters trying to emphasis the “good” correlation of the motorcycle position. I doubt the BBN would have overlooked any chance to bolster this. So, if a through examination of all 2,592 combinations had been made, Dr. Barger would have certainly driven this point home. To show the good estimates of the motorcycle position was valid and not based on a partial sampling of the data. The lack of such clear statements from Dr. Barger is an indicator to me, that the search of the matches was not a through search of all the data, all the 2,592, but was a partial sampling of the data. So that the search of the data for the “forward” microphones, was not done for the early shots, since no valid shot could be found there. And the search of the data for the “rearward” microphones, was not done for the later shots, since no valid shot could be found there. And time constraints may have made this search very focused for each shot except the first they looked for. Hence, the lack of so many wild estimates for the location of the motorcycle, as we get for the shooter location and the target location.

JFK Assassination Forum


Offline Michael T. Griffith

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That's around the windscreen. Our circus midget has no effing clue what he's talking about.
"we know from science" -- LOL

Oh . . . boy . . . . LOL indeed. It's actually both through and around, and sometimes authors pick one or the other. You'll notice that Dr. Chambers chose to say "through": "would pass through the windshield." Sound passes both through and goes around an object. That's why you can hear sounds from outside your car even if you have your windows rolled up. That's why you can hear sounds from outside your house even if you have all of your windows closed, or even if you're in a room with no windows. Rather than say "through and around" some authors just pick one or the other.

Anyway, moving on from Otto Beck's latest gaffe, I'd like to discuss a correlation that I have not discussed yet. The HSCA acoustical scientists noticed early on that about 3 seconds before the first gunshot on the police tape, the motorcycle's engine noise drops substantially. At that point in time, they did not understand the significance of this. Only later, after they did the test firing and then looked at the sound impulse data from the microphones, did they understand the importance of this. They realized that the drop in motorcycle noise corresponded to the time when the motorcycle would have slowed down to turn onto Houston Street! Dr. Barger:

Quote
Now, if you recall the first thing we noticed on the tape was that there was a diminution of the sound due to the motorcycle 3 seconds prior to the first impulsive pattern that we originally suspected could be caused by gunfire.

There was no obvious explanation for that, until one sees that at that time the motorcycle was just beginning a 110° turn, and on the inside track apparently, and he would therefore have to slow down to execute the turn. (2 HSCA 68)

And I see Mr. Elliott has apparently decided to stop trying to deal directly with the windshield-distortion correlations and is once again demanding answers to his irrelevant, error-based questions. Just to recap, the three TSBD shots contain windshield distortion because the patrolman's microphone was in a position where the gunshot sound waves would have encountered his windshield before reaching the microphone. But, for the grassy knoll shot, where the motorcycle was in a position where the windshield did not intervene between the gunshot sound waves and the microphone, there is no windshield distortion. Think about the number of factors that would have to come together to make these correlations possible. Here are just some of them:

* The motorcycle would have had to be in the correction positions on Houston Street and at the very beginning of Elm Street after turning off Houston Street for the windshield to be able to cause any distortion.

* The motorcycle would have had to be at point on Elm Street where the grassy knoll gunshot sound waves could have reached the microphone without being affected by the windshield in any measurable way.

* To get to the correct locations on Houston and Elm Streets in the first place, the motorcycle would have had to be moving at an average speed almost identical to that of the motorcade. 

* The motorcycle would have had to be far enough back in the motorcade to begin with in order to reach the required locations at the correct average speed.

Finally, here is an informative, instructive interview with Dr. Thomas on the acoustical evidence. The audio is very clear. The interview runs 34 minutes:

https://www.maryferrell.org/pages/Unredacted_-_Episode_4.html

Here's the transcript of the interview:

https://www.maryferrell.org/pages/Unredacted_-_Episode_4_-_Transcript.html

« Last Edit: September 29, 2020, 12:47:47 AM by Michael T. Griffith »