HSCA 1978 Acoustic Study by BBN – Figure 367

[Joe Elliott]

HSCA 1978 Acoustic Study by BBN Exhibit F-367

Beyond debate, somewhere in the Dallas area, one of the police motorcycles had a stuck key, so for several minutes it was broadcasting the sounds near the motorcycle, without the rider being aware of this. This was recorded on the Dictabelt. This was a common problem for the Dallas police back then, with many dozens of officers patrolling the streets, the odds were pretty good that someone would have a stuck key. While stuck, no other patrolman could talk on that Channel.

BBN was tasked trying to figure out if this motorcycle was at Dealey Plaza and recorded the gunshots. Curiously, it was believed possible that the recording did contain a record of the shots, even thought the “shots” did not sound like shots, or were even remotely similar to the sound of shots. More like static.

Bolt, Beranek and Newman (BBN) found two cluster of N-waves. Separated by about a minute. They focused on the first cluster.


The BBN report boils down to one table, shown below:

Test	Beginning Time of	Zap.	Zap.	Microphone Array	Rifle	Target	Correlation	Strong	Fluke
ID	First impulse on	Frame	Frame	and	Location	Location	Coefficient**
	Tape Segments (sec)	BBN	Thomas	(Channel Numbers)
A	136.20			No Correlations Higher Than			0.5
B	137.70	168	176	2 ( 5 )	TSBD*	1	0.8	Strong
C	137.70	168	176	2 ( 5 )	TSBD*	3	0.7		Fluke
D	137.70	168	176	2 ( 6 )	TSBD	3	0.8	Strong	Fluke
E	137.70	168	176	2 ( 6 )	KNOLL	4	0.7		Fluke
G	139.27	196	205	2 ( 6 )	TSBD*	3	0.8	Strong
H	139.27	196	205	2 ( 6 )	TSBD	3	0.6
I	139.27	196	205	2 ( 10 )	TSBD	3	0.6		Fluke
J	139.27	196	205	3 ( 5 )	KNOLL	3	0.6		Fluke
K	140.32	216	224	2 ( 11 )	TSBD*	3	0.6
L	145.15	304	313	3 ( 4 )	KNOLL	3	0.8	Strong
M	145.15	304	313	3 ( 7 )	TSBD*	2	0.7		Fluke
N	145.15	304	313	3 ( 8 )	TSBD	3	0.7		Fluke
O	145.61	313	321	3 ( 5 )	TSBD	3	0.8	Strong	Fluke
P	145.61	313	321	3 ( 6 )	TSBD	4	0.8	Strong
Q	145.61	313	321	3 ( 8 )	TSBD*	2	0.7	Fluke
R	146.30			No Correlations Higher Than			0.5

* Indicates Muzzle Withdrawn 2 ft from Plane of Window
** Correlation coefficient = number of experienced Matches with Impulses divided by the square root of the number of echoes X Number of impulses is Less than or equal to 1.0


I have modified this table a bit:

•   I added a “Test ID” column, so each test firing which gave a match can be identified as “A” through “R”.

•   I have added a “Zap. Frame BBN” column, to show the times the shots occurred, as estimated by BBN.
•   I have added a “Zap. Frame Thomas” column, to show the times the shots occurred, as estimated by Dr. Thomas.

The BBN and the Thomas Zapruder Frames are different, because BBN considered the last shot to be at z313, whereas Dr. Thomas considered the last shot to be at z321. In the rest of my post, when I refer to a shot at a Zapruder frame, like z224, I will be using Dr. Thomas’s frame number, not the BBN frame number.

The frame numbers I calculated myself, (reference frame + delta time * 18.3, rounded down) so they may vary slightly from other sources.

•   I have added a “Strong” column, to indicate which tests had a “Strong” correlation.
•   I have added a “Fluke” column, to indicate which tests had a correlation that was a “Fluke”

•   And I swapped Tests J and K so that all the results can be grouped with the other results of the same “shot”.



The Acoustic tests that BBN took a day to run back in 1978, consisted of placing 36 microphones along Houston Street and Elm Street, along sections they guessed the motorcycle with the stuck key may have passed through during the shooting. There were 78 test shots fired, which would give, according to my calculations, 78 * 36 or 2,808 test runs. Each test gunshot produced 36 test results, 36 separate recordings of each shot. They do this because the shape of the “N-wave”, if formed by a gunshot, is affected by:

•   The location of the microphone
•   The location of the rifle
•   The location of the target.

These gives a unique “fingerprint” for each “N-wave”.


BBN did not conclude that there were gunshots recorded on the Dictabelt recording because “sound impulses” or “N-waves” were found on it. These “N-waves” are found throughout the recording. And there are at least two cluster of “N-waves”, which are separated from each other by a minute. And a few other “N-waves” to be found here or there in the 5-minute recording. Since all the shots occurred within a 10 second period, it is impossible for all these “N-waves” to have been gunshots. So, it is clear that “N-waves” can be created by some other means then gunshots. Perhaps all of them were created by some other means.

BBN focused on the first cluster of 7 “N-waves”. They compared each of the 7 “N-waves” with the over 2,600 test runs. After comparing each of the 7 “N-waves” with each of the 36 recordings for each test shot, they found, among these 2,600 recordings, 18 near matches.

None of the matches were very good. The best was 0.8, which Wikipedia lists as a marginal result if good quality instruments are used. But, of course, I don’t imagine the Dictabelt would be considered a good quality instrument. But for whatever reason, no excellent matches were found.

It is evident that BBN considered anything less than a correlation coefficient of less than 0.8 to be irrelevant. Six of the matches had a correlation coefficient of 0.8. At least two of these must be flukes. Why is this true?

For the “z176” shot, we have two test results, Test B and D, both of 0.8. Both recorded near microphone 2 (5). But one shot was aimed at “Target 1” and another at “Target 3”. Both can’t be right. If in real life, a shot was fired at “Target 1”, Test B is a true match. But Test D was a fluke. There is the same problem with Test O and P with the z321 shot. Both were fired at two different targets. Only one can be a true match, the other must be a fluke.

So, of our 6 “matches”, at least two are flukes. Perhaps all 6 are flukes. With each of the 7 “N-waves” being compared to over 2,600 test results, it would not be surprising to get some correlations.

If Test L for the shot at z304 is considered a true match, as the BBN firm did, then Tests M and N are flukes, because it would be just a fluke that shots fired from the TSBD would have the same “fingerprint” of a shot fired from the Grassy Knoll.

Basically, I label any shot as a fluke, if a correlation was found for it, but a stronger correlation was found for a different test, and the BBN firm considered that test to have been the true match.


Basically, with each of the N-waves getting over 2,600 chances for a lucky match, 18 matches were found among the over 18,000 (2,600 times 7) possibilities. None of the matches were super strong. Many of them contradicted each other.



Now, let’s look at some other possible patterns. What was the progression of the “targets” during the shooting, to see if these correlations are valid? Only a test result with a “Strong” 0.8 coefficient will be considered. They were:

Shot z176   Target 1 or 3
Shot z205   Target 3
Shot z224   Target 3
Shot z313   Target 3
Shot z321   Target 3 or 4

This is not a good result. Most of the shots seemed to been fired at Target 3. Perhaps all were fired at Target 3. There should have been a progression of targets as time went on. Early shots at Target 1, then Target 2, then Target 3 and finally ending at Target 4.

If one cherry picks the targets, one could say the sequence was:

Shot z176   Target 1
Shot z205   Target 3
Shot z224   Target 3
Shot z313   Target 3
Shot z321   Target 4

Resulting in something like a progression. But there are still too many shots at Target 3, from z2205 through z313, over a period of 5.9 seconds. Surely the shooters were not all shooting at the same spot and ignoring where the limousine was at the moment.



But, let’s look at another pattern, the location of the microphone.

Shot z176   Microphone 2(5) or 2(6)
Shot z205   Microphone 2(6)
Shot z224   Microphone 2(11)
Shot z313   Microphone 3(4)
Shot z321   Microphone 3(5) or 3(6)

This is much, much better. A miserable progression for the location of the targets, but a much better progression for the location of the microphones.

What are the odds of this happening by luck? It is 5 Factorial, 5 * 4 * 3 * 2 * 1 or one in 120. With this result alone, one would think that BBN wouldn’t have said they had a 50-50 chance of a correlation due to luck (there initial assessment) or a 95% chance it was a true result. One would have thought they would say there were 99% certain that these were true results. Why didn’t they?


Let’s say that a man claims he can read minds, not all the time, but some of the time. In a controlled experiment (so no one is defrauded) he borrows a person’s Debit card, makes one attempt to read their minds, and then enters a PIN number. With 100 people he had 6 successes. But the odds of success in any one try is one in ten thousand. Surely, he must be psychic to have success six times in only one hundred attempts.

But not so fast. What if, all of his successful guesses were “1234”. This would not be evidence of psychic powers, but that some people make foolish choices about what their PIN numbers should be so they can remember them.


The test pattern for the location of the microphones could also be a linear result. For the tests in 1978, maybe the critical factor was the location of the microphone. For a shot from the TSBD, the “N-wave” may be largely determine by the location of the microphone. From when the first shock wave reached the microphone and when an echo of the non-supersonic muzzle blast from one of the buildings along Houston Street first reached it. In general, the further down Elm Street, the further the delay would be between when the shock wave first arrived and the slower echo arrived. This could result in a linear relationship of the test shots. A result of “12345” for the ever-increasing gap between the two waves.

And, if the 1963 Dictabelt’s N-waves were made in the same manner, and recorded within Dealey Plaza, it too would have the same linear relationship, showing the same “12345” pattern that we see in the 1978 tests. And be an indication that the Dictabelt does indeed record shots.

But if the 1963 Dictabelt recording was produced by a motorcycle at the Trademart Center, we might see the same “12345” pattern. Maybe these N-waves were made by someone somewhere in Dallas trying to transmit a message. They held down transmit key and this produced the “Static” heard on the recordings. Maybe the longer the transmit button is held down, the more it effects the N-waves that are produced. Resulting in the same “12345” pattern.


This correlation would be a lot more compelling, if we had Officer McLain on film, showing him riding up Elm Street, reversing direction, then reversing again. So, the expected pattern was not “12345”, but “13425”. And if the pattern on the Dictabelt was also “13425”, that would be quite interesting. Why would a recording made by a motorcycle at the Trademart center also produce a “13425” pattern? But finding both a “12345” pattern on the Dictabelt recording, and expecting that there was a “12345” pattern with the location of Officer McLain, is not nearly as compelling a coincidence. Not to me. And evidentially not to the experts at BBN.



A separate factor is, I’m certain these comparisons were done by computer back in 1979. Computers were a lot slower back then. Maybe they only ran comparisons for a certain N-wave over a certain range of data, perhaps figuring if a true match was found for the N-wave at 139.27 (z205) it has to be in the first third of the data. Any match found in the last third, would have to be a fluke. So, there would be no need to search for a match in the z280-z350 section. I don’t know if something like this was done, to save computer time, but it is a possibility. If so, that would also greatly affect the odds of only finding matches that fit the “12345” pattern.



Always be suspicious of a correlation between two sets, if both sets are ordered “12345”. It might not be as big a coincidence as one thinks. All that glitters is not gold.

All in all, I can see why BBN did not use this as a basis for their probability estimate. And since the correlation, even with up to 18,000 total comparisons did not result in any real strong correlations, I think they were right to initially say, the odds of this happening by luck are 50-50. Later, they were talked into making the odds of a lucky match at only 5 per cent. But their initial assessment was 50-50.



And finally, there is one more coincidence. The gap in time between the z224 “shot” and the z313 “shot” on the Dictabelt recording of 4.8 seconds. And a gap in time between the z224 shot and the z313 shot on the Zapruder film, which is also 4.8 seconds. That’s an amazing coincidence, right. There would be only a one in a hundred chance of there being a gap of 4.8 seconds between the “z224” N-wave and the “z313” N-wave, right? Yes. But remember, there weren’t just two N-waves. There were 7 N-waves in that cluster covering those 7.9 seconds. How many unique pairs are there between these 7 N-waves? The answer is 7 * 6 / 2 which is 21. These N-wave pairs are: AB, AC, AD, AE, AF, AG, BC, BD, BE, BF, BG, CD, CE, CF, CG, DE, DF, DG, EF, EG, and FG. So. the odds of a 4.8 second match between any of these two pairs is more like 1 in 5, not 1 in 100.

Also, there was a different cluster of N-waves a minute later that could have been tested but was not. It is possible, for all we know, that BBN focused on the first cluster because they knew it had a pair of N-waves 4.8 seconds apart and that the second cluster did not. And that was why they focused on that first cluster. So, the odds might even be greater than 1 in 5.

Note: On September 25, 2020, a minor correction was made to my table for BBN Exhibit F-367

[Michael T. Griffith]

Mr. Elliott's post is a comedy of errors. Folks, if you read Mr. Elliott's replies about the acoustical evidence in the "Poor Scholarship on Display" thread and in his own "Question about Dr. Donald Thomas’s Dictabelt Offset Hypothesis" thread, you will see that he has horrendously blundered over and over again when it comes to the acoustical evidence

Let's start with Elliott's opening statement:

ELLIOTT: HSCA 1978 Acoustic Study by BBN – Figure 367.

There is no Figure 367 in the BBN acoustical study. Somehow, Elliott misread BBN scientist James Barger's HSCA testimony as being the "HSCA 1978 Acoustic Study by BBN." The BBN acoustical study is in volume 8 of the HSCA volumes. Barger's testimony is in volume 2. Barger's testimony is where we find Figure 367. And anyone who reads Barger's testimony will quickly see that Elliott has grossly misrepresented, or misunderstood, the content and meaning of Figure 367.

Now let us address the heart of Mr. Elliott's post:

ELLIOTT: Bolt, Beranek and Newman (BBN) found two cluster of N-waves. Separated by about a minute. They focused on the first cluster. . . .

No, they did not find two clusters of N-waves. Such a claim shows a lack of understanding of even the basics of the BBN and WA acoustical research for the HSCA.

The "separated by about a minute" comment is based on Mr. Elliott's debunked claim that the Decker "hold everything" crosstalk is a valid time indicator and thus proves that the dictabelt gunshot impulse patterns were recorded 60 seconds after the assassination.

Elliott knows, or should know, that this is erroneous. There are five far more reliable time indicators that prove the gunshot impulse patterns were recorded during the assassination, namely, the simultaneous Fisher "I'll check" crosstalk, the Channel 2 dispatcher's 12:30 time notation, the Channel 1 dispatcher's 12:28 time notation, and Chief Curry's two assassination-period transmissions on Channel 2, both of which were made in Dealey Plaza. 

ELLIOTT: “N-waves” are found throughout the recording. And there are at least two cluster of “N-waves”, which are separated from each other by a minute. And a few other “N-waves” to be found here or there in the 5-minute recording. Since all the shots occurred within a 10 second period, it is impossible for all these “N-waves” to have been gunshots. So, it is clear that “N-waves” can be created by some other means then gunshots. Perhaps all of them were created by some other means.

No, N-waves are not found "throughout the recording." This is a comical, embarrassing error. Elliott either does not understand, or is hoping we do not understand, that there is a huge difference between N-waves and non-gunfire sounds that can look like N-waves when they are graphically illustrated on an oscillogram.

An actual N-wave, also known as a shock wave, is produced by a bullet traveling at supersonic speed. When a bullet is fired from a rifle, the N-wave will be recorded 15-30 milliseconds before the muzzle blast will be recorded, depending on the rifle's muzzle velocity and the ambient conditions when the N-wave was recorded. The muzzle blast, in turn, will be followed by the echoes of the muzzle blast. Also, the muzzle blast will be louder than the N-wave, so any N-wave graphed on an oscillogram will be followed by/come before a waveform with a higher/larger loudness peak, as Dr. Barger explained:

At the top of the illustration we show the acoustical waveforms of both the shock wave and the muzzle blast from a Mannlicher-Carcano . The shock wave was measured by a microphone 10 feet from the trajectory of the bullet and the muzzle blast was measured by the same microphone which was at the same time 30 feet from the muzzle.

All of the acoustical pressures are plotted here as a function of time measured in milliseconds . The shock wave is a very sharp event looking something like the letter "N," capital letter "N" and in this case, with this weapon, the peak pressure of the shock wave is 130 decibels.

Now let me just briefly describe the decibel as a measure of acoustical intensity. The reference pressure for the decibels that I describe is 2 times 10 to the minus 5 newtons per square meter, the currently standard reference pressure. With respect to that pressure, the shock wave has an intensity of 130 decibels.

The muzzle blast at 30 feet is more intense. It has an intensity of 137 decibels.

Let me just give you a few facts about decibels that will help make this clear.

If two sounds are otherwise similar but have a different loudness, a different intensity by 10 decibels, the louder of the two will sound twice as loud . On the other end of the scale, if two sounds are so slightly different in intensity that you can just perceive that difference, they will be different by 3 decibels.

The muzzle blast then, more intense by 7 decibels, would sound almost twice as loud as the shock wave. It has a very sharp peak, a negative undershoot followed by quiescence, and these are characteristic of the waveforms of that rifle.(2 HSCA 23)

Barger noted that with both the Mannlicher-Carcano rifle and the M-1 rifle, the muzzle blast was louder than the N-wave (2 HSCA 22). This same is true for bullets fired from a Winchester .308 rifle (https://www.montana.edu/rmaher/publications/maher_aac_0406.pdf).

The dictabelt contains some bursts of static. When the sound waveforms of static are graphed on an oscillogram, they can look exactly like N-waves, because the graphical representation is just a graphical display of their loudness, nothing more. If someone yells into a microphone, the waveform of their yell will look like an N-wave on an oscillogram. However, such non-gunfire noises will not come 15-30 milliseconds before a muzzle blast and before the subsequent echoes of the muzzle blast, and their acoustical fingerprints will not match, in the correct topographic order, those of shots fired in the location they were recorded. So, of course, nobody but a rank amateur, or someone trying to mislead, would claim that the static or the yell was actually an N-wave.

BBN did not conclude that there were gunshots recorded on the Dictabelt recording because “sound impulses” or “N-waves” were found on it.

This bizarre statement is further proof that Elliott simply has no clue what he's talking about, or else it shows he is willing to knowingly misrepresent the acoustical evidence. The part about "sound impulses" is just silly. The part about the N-waves is demonstrably wrong. The HSCA acoustical experts made it clear that the presence of N-waves on the dictabelt was important evidence that the recording contains gunfire. I quote from the HSCA's report:

In addition, Barger emphasized, the first part of the sequence of impulses identified as a shot from the grassy knoll was marked by an N-wave, a characteristic impulse caused by a supersonic bullet.(61) The N-wave, also referred to as a supersonic shock wave, travels faster than the noise of the muzzle blast of a gun and therefore arrives at a listening device such as a microphone ahead of the noise of a muzzle blast. The presence of the N-wave was, therefore, a significant additional indication that the third impulse on the police dispatch tape represented gunfire, and, in particular, a supersonic bullet.(62) The weapon may well have been a rifle, since most pistols except for some such as a .44 magnum--fire subsonic bullets.

The N-wave was further substantiation for a finding that the third impulse represented a shot fired in the direction of the President. Had the gun been discharged when aimed straight up or down, or away from the motorcade, no N-wave would have appeared.(63) Of the impulse patterns on the dispatch tape that indicated shots from the book depository, those that would be expected to contain an N-wave, given the location of the vehicle's microphone, did so, further corroborating the conclusion that these impulses did represent supersonic bullets.(64) (HSCA Report, pp. 74-75)

 

I have been asking Mr. Elliott for weeks now to address the powerful, intricate correlations between the gunshot impulse patterns on the dictabelt and the gunshots from the Dealey Plaza test firing. The following articles give a good overview of these correlations:

https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_2.html

https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_3.html

https://the-puzzle-palace.com/rebuttal.htm

And here is a helpful video by Dr. Donald Thomas:

https://aarclibrary.org/dr-donald-b-thomas-jfk-acoustical-evidence-challenge-and-corroboration/

[Joe Elliott]

Mr. Elliott's post is a comedy of errors. Folks, if you read Mr. Elliott's replies about the acoustical evidence in the "Poor Scholarship on Display" thread and in his own "Question about Dr. Donald Thomas’s Dictabelt Offset Hypothesis" thread, you will see that he has horrendously blundered over and over again when it comes to the acoustical evidence

Let's start with Elliott's opening statement:

There is no Figure 367 in the BBN acoustical study. Somehow, Elliott misread BBN scientist James Barger's HSCA testimony as being the "HSCA 1978 Acoustic Study by BBN." The BBN acoustical study is in volume 8 of the HSCA volumes. Barger's testimony is in volume 2. Barger's testimony is where we find Figure 367. And anyone who reads Barger's testimony will quickly see that Elliott has grossly misrepresented, or misunderstood, the content and meaning of Figure 367.

This is making a mountain out of a molehill. The statements of Dr. Barger to the HSCA were technically not the “written” report, but was his verbal “report” of his company’s work on this project to the HSCA. Figure 337 provides a good summary on the basis of their conclusions.

Now let us address the heart of Mr. Elliott's post:

No, they did not find two clusters of N-waves. Such a claim shows a lack of understanding of even the basics of the BBN and WA acoustical research for the HSCA.

The "separated by about a minute" comment is based on Mr. Elliott's debunked claim that the Decker "hold everything" crosstalk is a valid time indicator and thus proves that the dictabelt gunshot impulse patterns were recorded 60 seconds after the assassination.

No. My statement about other N-waves is not based on the “hold everything” crosstalk. It is Mr. Griffith who is misinformed. It is based on the statement made by Dr. Barger to the HSCA:

http://mcadams.posc.mu.edu/russ/m_j_russ/hscabarg.htm

Mr. CORNWELL - Moving next to the second screening test that you mentioned, namely, whether the impulses were unique, I would like to ask you if you would describe what you did to determine the answer to that question.
Dr. BARGER - Yes. We examined the full 234 linear feet of the waveform representing the output of the channel 1 recording when the button was stuck to see if there were any other impulsive patterns that occurred that were similar to these that we are looking at on channel 1. We found that there was one other sequence of impulsive events. It was dissimilar from the one we have looked at principally in that its timespan was less than 5 seconds. It occurred about a minute later than the period of impulses in question. We found no other impulsive patterns on the tape.

So, there are at least two clusters of “impulse patterns”, events with multiple “impulses” or N-waves. Both were similar, except the first one spanned at time of 10.1 seconds and contained 7 impulses. The second cluster was a minute later, contained an unspecified number of impulses, and covered less than 5 seconds. No where does he state that this second set of impulses were in any way fundamentally different from the first set of impulses. Instead, he was able to judge that this second set of “impulse patterns” was not of interest only because it spanned less than 5 seconds, too short to be all the gunshots.

If my claim is a ‘lie’, that there are other unexplained “impulse patterns” found on the Dictabelt that were not gunshots, I am not the original liar. The ‘lie’ originated with Mr. Griffith’s hero, Dr. Barger. Don’t blame me if you think this is a lie. Go blame Dr. Barger.


From what I have read elsewhere, there are other isolated N-waves scattered here and there on the Dictabelt, basically sounding like static. In the 5-minute section of interest, there were these two clusters of N-waves, separated by a minute. They can’t all be gunshots because no one believes the shooting occurred over a span of a minute. Some of these N-waves must be non-gunshots. And perhaps, all of them are non-gunshots.

I believe that there were other N-waves, in the 5-minute period, despite Dr. Barger’ statement:  We found no other impulsive patterns on the tape.

Mr. CORNWELL - Moving next to the second screening test that you mentioned, namely, whether the impulses were unique, I would like to ask you if you would describe what you did to determine the answer to that question.
Dr. BARGER - Yes. We examined the full 234 linear feet of the waveform representing the output of the channel 1 recording when the button was stuck to see if there were any other impulsive patterns that occurred that were similar to these that we are looking at on channel 1. We found that there was one other sequence of impulsive events. It was dissimilar from the one we have looked at principally in that its timespan was less than 5 seconds. It occurred about a minute later than the period of impulses in question. We found no other impulsive patterns on the tape.

I believe he means no other “cluster” of impulse patterns, and was not referring to no other similar isolated impulses during the 5-minute period. If that is not what he meant, well, that would contradict what I have read elsewhere, that there are other isolated N-waves scattered over the 5-minute period in question, while the transmit key was stuck.

Who knows how many such clusters would be found on the Dictabelt recording if the whole thing was every carefully checked for such clusters, and not just that 5-minute segment?

Even of the 7 N-waves of the cluster the BBN looked at, the BBN concluded that 3 of them were probably not formed by gunshots, because they could not match them up with their firing tests which took place at Dealey Plaza. Later, Dr. Thomas claimed one of these rejected N-waves was a real gunshot. You claim the BBN rejected this as a shot solely because Robert Blakey would not accept more than 4 shots. But in actual truth, the BBN found that there was a weak correlation coefficient of 0.6 for the shot at z224 (Dr. Thomas’s estimate). All the other 4 “shots” that they did accept, had a correlation coefficient of 0.8, which is still not very strong, but at least better than 0.6. All this is to be found in Figure 337, provided by Dr. Barger, which is quite helpful in evaluating which of these alleged shots have the most support.

Now, it may be that the three “Rejected” N-waves really were gunshots, fired from locations that the BBN did not test, because, of course, it was impossible to run tests firing rifles from every possible firing position. But the point is, that even Dr. Barger accepted that some of these “Sound Impulses” might not have been formed from gunfire. And probably were not. As opposed to Mr. Griffith who believes that all such “Sound Impulses” can only be caused by a gunshot and that there is no other possible explanation.

So, even the BBN concluded that many of the N-wave patterns, even some of those found in the 10.1 second cluster, were not caused by gunshots.

No, N-waves are not found "throughout the recording." This is a comical, embarrassing error. Elliott either does not understand, or is hoping we do not understand, that there is a huge difference between N-waves and non-gunfire sounds that can look like N-waves when they are graphically illustrated on an oscillogram.

Wrong, see above. While Dr. Barger did not comment on this, I do remember reading that similar noises, which sound like static, are to be found throughout the recording. And we know of two such clusters, covering 5 to 10 seconds.

An actual N-wave, also known as a shock wave, is produced by a bullet traveling at supersonic speed. When a bullet is fired from a rifle, the N-wave will be recorded 15-30 milliseconds before the muzzle blast will be recorded, depending on the rifle's muzzle velocity and the ambient conditions when the N-wave was recorded. The muzzle blast, in turn, will be followed by the echoes of the muzzle blast. Also, the muzzle blast will be louder than the N-wave, so any N-wave graphed on an oscillogram will be followed by/come before a waveform with a higher/larger loudness peak, as Dr. Barger explained:

Wrong. Dr. Barger himself there were similar impulses a minute after the “gunshot” cluster. But rejected as gunshots because it spanned less than 5 seconds. He made no statement that the nature of these impulses was in any way fundamentally different from the impulses in the 10.1 second section they did study carefully. It was just that this second cluster lasted under 5 seconds, while the first cluster lasted 10.1 seconds. And it was for that reason they focused on the first cluster.
 

I have been asking Mr. Elliott for weeks now to address the powerful, intricate correlations between the gunshot impulse patterns on the dictabelt and the gunshots from the Dealey Plaza test firing. The following articles give a good overview of these correlations:

https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_2.html

https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_3.html

https://the-puzzle-palace.com/rebuttal.htm

And here is a helpful video by Dr. Donald Thomas:

https://aarclibrary.org/dr-donald-b-thomas-jfk-acoustical-evidence-challenge-and-corroboration/

The correlation of the shots in time with their position in Dealey Plaza? I am working on that now. I should have a new topic on this in a day or two.

[Michael T. Griffith]

Quote from: Michael T. Griffith
No, they did not find two clusters of N-waves. Such a claim shows a lack of understanding of even the basics of the BBN and WA acoustical research for the HSCA.

The "separated by about a minute" comment is based on Mr. Elliott's debunked claim that the Decker "hold everything" crosstalk is a valid time indicator and thus proves that the dictabelt gunshot impulse patterns were recorded 60 seconds after the assassination.

Quote from: Joe Elliott
No. My statement about other N-waves is not based on the “hold everything” crosstalk. It is Mr. Griffith who is misinformed. It is based on the statement made by Dr. Barger to the HSCA:

Quote
Mr. CORNWELL - Moving next to the second screening test that you mentioned, namely, whether the impulses were unique, I would like to ask you if you would describe what you did to determine the answer to that question.
Dr. BARGER - Yes. We examined the full 234 linear feet of the waveform representing the output of the channel 1 recording when the button was stuck to see if there were any other impulsive patterns that occurred that were similar to these that we are looking at on channel 1. We found that there was one other sequence of impulsive events. It was dissimilar from the one we have looked at principally in that its timespan was less than 5 seconds. It occurred about a minute later than the period of impulses in question. We found no other impulsive patterns on the tape.

You seem sincere here, but you are badly confused. Dr. Barger was talking about the waveforms after they were graphed and displayed on oscillograms and spectrograms. He was simply talking about how they appeared on the oscillograms and spectrograms and the analysis of their appearance before they began the screening tests. They had not even done the Dealey Plaza test firing yet. None of the screening criteria involved checking for N-waves and muzzle blasts.

BBN converted the sounds on the tape into digitized waveforms and produced a visual representation of the waveforms (the oscillograms and spectrograms). Once they did this and filtered out the engine noise, they examined the dictabelt for "sequences of impulses" that might be significant. Six sequences of impulses that could have been caused by a noise such as gunfire were initially identified as having been transmitted over Channel 1.

These are the six "sequences of impulses" to which BBN applied the preliminary screening tests to determine if any could be conclusively determined not to have been caused by gunfire during the assassination.

Just to be crystal clear, here are the six criteria that were used for the preliminary screening tests--I'm quoting from the HSCA report:

-- Do the impulse patterns, in fact, occur during the period of the assassination?
-- Are the impulse patterns unique to the period of the assassination?
-- Does the span of time of the impulse patterns approximate the duration of the assassination as indicated by a preliminary analysis of the Zapruder film? Are there at least 5.6 seconds between the first and last impulse?
-- Does the shape of the impulse patterns resemble the shape of impulse patterns produced when the sound of gunfire is recorded through a radio transmission system comparable to the one used the Dallas police dispatch network?
-- Are the amplitudes of the impulse patterns similar to those produced when the sound of gunfire is recorded through a transmission system comparable to the one used for the Dallas police dispatch network?

All six of the "sequences of impulses" passed these preliminary screening tests. Note that none of the screening criteria had anything to do with N-waves and muzzle blasts. These screening criteria were more basic than that.

Quote from: Joe Elliott
So, there are at least two clusters of “impulse patterns”, events with multiple “impulses” or N-waves. Both were similar, except the first one spanned at time of 10.1 seconds and contained 7 impulses. The second cluster was a minute later, contained an unspecified number of impulses, and covered less than 5 seconds. No where does he state that this second set of impulses were in any way fundamentally different from the first set of impulses. Instead, he was able to judge that this second set of “impulse patterns” was not of interest only because it spanned less than 5 seconds, too short to be all the gunshots.

If my claim is a ‘lie’, that there are other unexplained “impulse patterns” found on the Dictabelt that were not gunshots, I am not the original liar. The ‘lie’ originated with Mr. Griffith’s hero, Dr. Barger. Don’t blame me if you think this is a lie. Go blame Dr. Barger.

No, it's just that you have totally misunderstood what Barger was talking about. 

Quote from: Joe Elliott
From what I have read elsewhere, there are other isolated N-waves scattered here and there on the Dictabelt, basically sounding like static. In the 5-minute section of interest, there were these two clusters of N-waves, separated by a minute. They can’t all be gunshots because no one believes the shooting occurred over a span of a minute. Some of these N-waves must be non-gunshots. And perhaps, all of them are non-gunshots.

You are once again totally misreading/misunderstanding what Barger and the other scientists were saying. BBN and WA never said there were N-waves "scattered here and there" on the dictabelt. Nobody ever made any such claim. You are confusing the observation of oscillogram/spectrogram resemblances between non-gunfire noises and N-waves and muzzle blasts with someone saying that there were N-waves throughout the dictabelt.

All kinds of sounds can create similar-looking spikes/peaks when graphed on an oscillogram and a spectrogram, but no acoustical scientist in his right mind would look at those similar-looking patterns and, without any further analysis, say, "Oh, there are a bunch of N-waves on the recording." What he would do is then look to see if muzzle-blast patterns were recorded 10-30 milliseconds after the N-wave-like patterns; he would also look to see if the muzzle-blast patterns were stronger than the N-wave-similar patterns; and he would further look to see if the muzzle-blast patterns were followed by patterns of echoes of those muzzle blasts. If the N-wave-similar patterns did not meet these criteria, then he would know they were not N-waves.

I don't know how to explain it any more simply. 

Quote from: Joe Elliott
I believe that there were other N-waves, in the 5-minute period, despite Dr. Barger’ statement:  "We found no other impulsive patterns on the tape." [SNIP OF REPEAT OF BARGER QUOTE]

I believe he means no other “cluster” of impulse patterns, and was not referring to no other similar isolated impulses during the 5-minute period. If that is not what he meant, well, that would contradict what I have read elsewhere, that there are other isolated N-waves scattered over the 5-minute period in question, while the transmit key was stuck.

No, you're still badly misreading/misunderstanding what he was talking about. Again, when Dr. Barger used the term "impulsive patterns" here, he was talking about impulse patterns that BBN tested with very basic screening criteria, as I've discussed above.

Quote from: Joe Elliott
Who knows how many such clusters would be found on the Dictabelt recording if the whole thing was every carefully checked for such clusters, and not just that 5-minute segment?

Same misunderstanding and misreading of Barger's testimony and of the other HSCA materials.

Quote from: Joe Elliott
Even of the 7 N-waves of the cluster the BBN looked at, the BBN concluded that 3 of them were probably not formed by gunshots, because they could not match them up with their firing tests which took place at Dealey Plaza. Later, Dr. Thomas claimed one of these rejected N-waves was a real gunshot. You claim the BBN rejected this as a shot solely because Robert Blakey would not accept more than 4 shots. But in actual truth, the BBN found that there was a weak correlation coefficient of 0.6 for the shot at z224 (Dr. Thomas’s estimate). All the other 4 “shots” that they did accept, had a correlation coefficient of 0.8, which is still not very strong, but at least better than 0.6. All this is to be found in Figure 337, provided by Dr. Barger, which is quite helpful in evaluating which of these alleged shots have the most support.

Wow, now you're really getting confused. There were no "rejected" N-waves. That is not how BBN and WA accepted or rejected a suspect impulse pattern. Dr. Thomas does not say that this or that N-wave was rejected. He says that the fourth suspect impulse pattern was rejected on non-acoustical grounds, and he notes that Dr. Barger later admitted to him that the reason BBN rejected it was "ad hoc" and circular.

Quote from: Joe Elliott
Now, it may be that the three “Rejected” N-waves really were gunshots, fired from locations that the BBN did not test, because, of course, it was impossible to run tests firing rifles from every possible firing position. But the point is, that even Dr. Barger accepted that some of these “Sound Impulses” might not have been formed from gunfire. And probably were not. As opposed to Mr. Griffith who believes that all such “Sound Impulses” can only be caused by a gunshot and that there is no other possible explanation.

So, even the BBN concluded that many of the N-wave patterns, even some of those found in the 10.1 second cluster, were not caused by gunshots.

No, BBN said nothing of the kind. You are continuing to confuse the basic screening of impulse sequences with the later analysis of N-waves and muzzle blasts. Again, go read the screening criteria: not one of them even mentions N-waves or muzzle blasts. 

Quote from: Michael T. Griffith on Today at 01:14:07 PM
No, N-waves are not found "throughout the recording." This is a comical, embarrassing error. Elliott either does not understand, or is hoping we do not understand, that there is a huge difference between N-waves and non-gunfire sounds that can look like N-waves when they are graphically illustrated on an oscillogram.

Quote from: Joe Elliott
Wrong, see above.

No, I am not wrong, and your comments above do not even remotely touch my point. 

Quote from: Joe Elliott
While Dr. Barger did not comment on this, I do remember reading that similar noises, which sound like static, are to be found throughout the recording. And we know of two such clusters, covering 5 to 10 seconds.

Yes! Yes, "similar noises" and "static." BBN and WA discussed these phenomena in some detail and explained how they distinguished them from gunfire! Each of the three suspect impulse patterns on the dictabelt that were recorded when the microphone was in a position to record shockwaves contain a shockwave followed by a muzzle blast, and the shockwaves and the muzzle blasts occur in the right order and in the right interval. An N-wave (shockwave) comes 10-30 milliseconds before the muzzle blast, and the muzzle blast is followed by muzzle-blast echoes. 

Quote from: Michael T. Griffith on Today at 01:14:07 PM
An actual N-wave, also known as a shock wave, is produced by a bullet traveling at supersonic speed. When a bullet is fired from a rifle, the N-wave will be recorded 15-30 milliseconds before the muzzle blast will be recorded, depending on the rifle's muzzle velocity and the ambient conditions when the N-wave was recorded. The muzzle blast, in turn, will be followed by the echoes of the muzzle blast. Also, the muzzle blast will be louder than the N-wave, so any N-wave graphed on an oscillogram will be followed by/come before a waveform with a higher/larger loudness peak, as Dr. Barger explained:

Quote from: Joe Elliott
Wrong.

"Wrong"? Go do a Google search on "shockwaves" and "gunfire." This is basic stuff. No, I am not wrong, and I notice you snipped out my quote from Barger where he explained that the muzzle blast will be louder than the N-wave. The BBN report explains that gunfire comes with N-waves (shock waves), muzzle blast, and muzzle-blast echoes:

The waveforms shown in this figure were produced by a Mannlicher-Carcano with Western Cartridge Co . ammunition and picked up by a microphone positioned 30 ft from the muzzle and 10 ft to one side of the bullet's trajectory. The muzzle blast waveform reveals a peak pressure impulse having a sound pressure level of 137 dB re 2x10 -SN/m 2. For comparison, Fig. 3 also shows the corresponding waveforms for an M-1 rifle.

Despite the differences in loudness (amplitude) from one weapon to the other, the shock wave and the muzzle blast can be seen to have characteristic shapes . Sounds processed from the Channel 1 tape could be expected to contain these shapes, but in distorted fashion. The shapes could be expected to be compressed in amplitude and to be accompanied by . indications of overdriving of the radio circuits. They would also be accompanied by waveforms produced by the arrival of sound echoes from several sources, as described in the rest of this section. (2 HSCA 16)

Quote from: Joe Elliott
Dr. Barger himself there were similar impulses a minute after the “gunshot” cluster.

"Similar" only in a superficial, cursory sense. That's why BBN then did the screening tests, and then did more tests after they identified six plausible gunfire candidates with the initial screening tests. I don't understand why you cannot grasp this basic, non-technical fact.
 

Quote from: Joe Elliott
But rejected as gunshots because it spanned less than 5 seconds. He made no statement that the nature of these impulses was in any way fundamentally different from the impulses in the 10.1 second section they did study carefully. It was just that this second cluster lasted under 5 seconds, while the first cluster lasted 10.1 seconds. And it was for that reason they focused on the first cluster.

Same severe misunderstanding/misreading of Barger's testimony and of the other HSCA acoustical research materials. The BBN report, which you really need to read, explains that after they did the five screening tests, they moved on to the more sophisticated tests based on an analysis of the dictabelt suspect impulse patterns and the impulse patterns from the test-firing shots:

Because the five screening tests described in Sec. 4 had failed to disprove the possibility of gunfire having been recorded on the Channel 1 tape, a more rigorous test was required. The objective of the acoustical reconstruction, therefore, was to obtain several "acoustical fingerprints" of the sound of gunfire in Dealey Plaza to compare with the impulse patterns found on the Channel 1 tape. If any of the "fingerprints" matched, then the reconstruction would result in determining both the timing of the shots and the locations of the weapon and the target for each shot. (2 HSCA 80)

Quote from: Joe Elliott
The correlation of the shots in time with their position in Dealey Plaza? I am working on that now. I should have a new topic on this in a day or two.

I hope to high heaven you won't do so until you have read chapters 16-18 in Dr. Thomas's book, the W&A report to the HSCA, and W&A's HSCA testimony.
 

[Joe Elliott]

No, they did not find two clusters of N-waves. Such a claim shows a lack of understanding of even the basics of the BBN and WA acoustical research for the HSCA.

The "separated by about a minute" comment is based on Mr. Elliott's debunked claim that the Decker "hold everything" crosstalk is a valid time indicator and thus proves that the dictabelt gunshot impulse patterns were recorded 60 seconds after the assassination.

No. My statement about other N-waves is not based on the “hold everything” crosstalk. It is Mr. Griffith who is misinformed. It is based on the statement made by Dr. Barger to the HSCA:

http://mcadams.posc.mu.edu/russ/m_j_russ/hscabarg.htm

You seem sincere here, but you are badly confused. Dr. Barger was talking about the waveforms after they were graphed and displayed on oscillograms and spectrograms. He was simply talking about how they appeared on the oscillograms and spectrograms and the analysis of their appearance before they began the screening tests. They had not even done the Dealey Plaza test firing yet. None of the screening criteria involved checking for N-waves and muzzle blasts.

They had not even done the Dealey Plaza test firing yet?


This is the testimony from September 11, 1978:

https://archive.org/stream/HouseSelectCommitteeOnAssassinations/Volume%202_djvu.txt


Below is the link I provided earlier, with just the September 11, 1978 testimony of Dr. James Barger.

http://mcadams.posc.mu.edu/russ/m_j_russ/hscabarg.htm


And a third link, showing the acoustic tests were run on August 27, 1978.

https://www.jfk-online.com/nas02.html

The BRSW team began by listening to tape copies of the recordings of both police radio channels for general orientation. Because the recorders were sound-activated, they could have stopped frequently for varying amounts of time, except that the Channel I recorder ran continuously for 5.5 minutes when a transmitter, presumably on a police motorcycle, became stuck in the transmit mode (the Channel I recorder appears to have run continuously during the period of interest). Using the frequent annotations of time by dispatchers on both channels, BRSW estimated the approximate time of the beginning and end of this 5 1/2 minute stuck-button transmission. Because of the severe noise and distortion on the recording, the BRSW team could neither confirm that this segment contained gunshot sounds, nor eliminate the possibility that they were present, by simple listening or by examining the waveforms of sounds on the tape. Therefore, they went to Dealey Plaza in Dallas August 27, 1978, and made recordings of test shots with various kinds of guns and ammunition, two shooter locations, and many microphone locations along the approximate route of the motorcade. For each combination of shooter location and microphone location, there is a characteristic and complex pattern of echoes in the recording of the test shot, because after the first sounds travel by a direct path to the microphone (usually the bullet shock wave and the muzzle blast sound), subsequent sounds arrive (due to echoes from buildings and other large objects) with varying delays, depending on the length of the path they have taken. A typical test shot waveform, made with a shooter and 3 microphone locations close to those later claimed for an assassination shot from the knoll, is shown in Figure 1.

So, actually the acoustic tests had already been run.

August 27, 1978: The Dealey Plaza firing tests were conducted and recordings of test rifle firings were made.
September 11, 1978: Dr. Barger testified that they had analyzed the data and gave the results of what they had found. And it was here that he talked about the two impulse sequences that they had found on the Dictabelt recording.

You keep making false statement after false statement and never acknowledge your previous mistakes.



And again, hear is the relevant passage:

Mr. CORNWELL - Moving next to the second screening test that you mentioned, namely, whether the impulses were unique, I would like to ask you if you would describe what you did to determine the answer to that question.
Dr. BARGER - Yes. We examined the full 234 linear feet of the waveform representing the output of the channel 1 recording when the button was stuck to see if there were any other impulsive patterns that occurred that were similar to these that we are looking at on channel 1. We found that there was one other sequence of impulsive events. It was dissimilar from the one we have looked at principally in that its timespan was less than 5 seconds. It occurred about a minute later than the period of impulses in question. We found no other impulsive patterns on the tape.

Dr. Barger says that there were not one but two Impulse Sequences. They occur one minute apart.

First Impulse Sequence: 10.1 seconds long.

Second Impulse Sequence: Less than 5seconds long.

What was the difference between the two Impulse Sequences? The only explicit difference that Dr. Barger said was the length of the sequence. Since they were satisfied, from the Zapruder film that the shooting had lasted at least 5.6 seconds. So that factor alone eliminated the second sequence.

There is nothing in his testimony that there was a fundamental difference in these two sequences. That the first set of impulses were N-waves that could only be caused by shock waves, but the second set were of a completely different nature that could have been caused by ordinary sounds. From what Dr. Barger says, the two sequences were similar, just of different length, and on that basis alone, he discounted the second sequence.


Question:

Exactly where does Dr. Barger say, they carefully compared the first Impulse Sequence with the second Impulse Sequence? And found that the Impulses in the second sequence are nothing like the impulses in the first. And so, the impulses in the first sequence were, or mostly were gunshots, but the impulses in second sequence were not.

As far as I know, no just close study was ever done by Dr. Barger or anyone else.

My guess, is that you will dodge this question.

So, it appears that there are two impulse sequences in the 5.5-minute period when the transmitter key was stuck. And probably others on other portions of the tape.

[Michael T. Griffith]

They had not even done the Dealey Plaza test firing yet?

This is the testimony from September 11, 1978:

https://archive.org/stream/HouseSelectCommitteeOnAssassinations/Volume%202_djvu.txt

Below is the link I provided earlier, with just the September 11, 1978 testimony of Dr. James Barger.

http://mcadams.posc.mu.edu/russ/m_j_russ/hscabarg.htm

And a third link, showing the acoustic tests were run on August 27, 1978.

https://www.jfk-online.com/nas02.html

So, actually the acoustic tests had already been run.

August 27, 1978: The Dealey Plaza firing tests were conducted and recordings of test rifle firings were made.
September 11, 1978: Dr. Barger testified that they had analyzed the data and gave the results of what they had found. And it was here that he talked about the two impulse sequences that they had found on the Dictabelt recording.

You keep making false statement after false statement and never acknowledge your previous mistakes.

And again, hear is the relevant passage:

Dr. Barger says that there were not one but two Impulse Sequences. They occur one minute apart.

First Impulse Sequence: 10.1 seconds long.

Second Impulse Sequence: Less than 5seconds long.

What was the difference between the two Impulse Sequences? The only explicit difference that Dr. Barger said was the length of the sequence. Since they were satisfied, from the Zapruder film that the shooting had lasted at least 5.6 seconds. So that factor alone eliminated the second sequence.

There is nothing in his testimony that there was a fundamental difference in these two sequences. That the first set of impulses were N-waves that could only be caused by shock waves, but the second set were of a completely different nature that could have been caused by ordinary sounds. From what Dr. Barger says, the two sequences were similar, just of different length, and on that basis alone, he discounted the second sequence.

Question:

Exactly where does Dr. Barger say, they carefully compared the first Impulse Sequence with the second Impulse Sequence? And found that the Impulses in the second sequence are nothing like the impulses in the first. And so, the impulses in the first sequence were, or mostly were gunshots, but the impulses in second sequence were not.

As far as I know, no just close study was ever done by Dr. Barger or anyone else.

My guess, is that you will dodge this question.

So, it appears that there are two impulse sequences in the 5.5-minute period when the transmitter key was stuck. And probably others on other portions of the tape.

Unbelievable. Just unbelievable.

The Dealey Plaza test firing was not conducted until BBN felt they had done as much screening and analysis as they thought could do without having test-firing data against which to compare the dictabelt data. At the time of the initial screening tests that Dr. Barger was discussing in his testimony, the test firing had not been done yet. BBN recommended that a test firing be done because of the results they had obtained from the screening tests.

So, no, I did not make a false statement when I made the factual observation that at the point in time that Dr. Barger was discussing, i.e., the initial screening tests, the test firing had not yet been conducted. How can you not know this? How? This is basic stuff that is a matter of record.

As for the N-waves and muzzle blasts, in the statements you quoted from Dr. Barger, go read the screening criteria again. Can you not see that they say nothing about N-waves and muzzle blasts? If you cannot understand this, or if you refuse to admit it, there is no point in further discussion with you on the subject. At this point, BBN did not know that each of the three suspect impulse patterns on the dictabelt that were recorded when the microphone was in a position to record the N-wave followed by its muzzle blast contain an N-wave, a muzzle blast, and muzzle-blast echoes, and the shockwaves and the muzzle blasts occur in the correct order and in the right interval. 

I made a good-faith effort to explain why your claim that the scientists found N-waves "scattered here and there" throughout dictabelt is erroneous. I even explained to you how they identified the N-waves, and the fact that no other sound impulse patterns on the dictabelt are followed 10-30 milliseconds later by a muzzle blast and by echoes from the muzzle blast. But you just don't want to hear it because you know that this is powerful evidence that the dictabelt contains assassination gunfire, just as the HSCA acoustical scientists said and just as the HSCA report noted.

As for your plan to address the correlations between the dictabelt gunshot impulse patterns and the test-firing gunshot impulse patterns, again, I hope to high heaven that you first read the relevant chapters in Dr. Thomas's book, the W&A acoustical report, and W&A's HSCA testimony.

But, really, you might want to hold off until Dr. Josiah Thompson's book Last Second in Dallas comes out later this year. It will contain a detailed defense and confirmation of the acoustical evidence. Dr. Barger and Dr. Thomas have been working with Dr. Thompson on this section of the book for the last few years, and the section will include the results from new acoustical tests.

[Joe Elliott]

Unbelievable. Just unbelievable.

The Dealey Plaza test firing was not conducted until BBN felt they had done as much screening and analysis as they thought could do without having test-firing data against which to compare the dictabelt data. At the time of the initial screening tests that Dr. Barger was discussing in his testimony, the test firing had not been done yet. BBN recommended that a test firing be done because of the results they had obtained from the screening tests.

Ok, I am done talking to Mr. Griffith on this issue. I will let other readers judge for themselves.


Here is the link that refers to the Dealey Plaza firing tests taking place on August 27, 1978 (second paragraph):

https://www.jfk-online.com/nas02.html



Here is link to various testimonies over several days, including the September 11, 1978 testimony by Dr. Barger where he:
•   Presents the work he and his team did on the Dealey Plaza firing tests in Exhibit F-367.
•   Discusses finding two impulse sequences, separated by a minute, showing that an impulse sequence can be created, even without gunshots.

https://archive.org/stream/HouseSelectCommitteeOnAssassinations/Volume%202_djvu.txt


And finally, a link to just the Dr. Barger testimony, which includes links to the figures he presented, including the all-important Exhibit F-367, which summaries the result of the August 27 Dealey Plaza firing tests, which Mr. Griffith keeps claiming have not been conducted yet.

http://mcadams.posc.mu.edu/russ/m_j_russ/hscabarg.htm


I’ll let the other members of this forum judge if I am telling the truth or him.

[Michael T. Griffith]

Ok, I am done talking to Mr. Griffith on this issue. I will let other readers judge for themselves.

Here is the link that refers to the Dealey Plaza firing tests taking place on August 27, 1978 (second paragraph):

https://www.jfk-online.com/nas02.html

Here is link to various testimonies over several days, including the September 11, 1978 testimony by Dr. Barger where he:
•   Presents the work he and his team did on the Dealey Plaza firing tests in Exhibit F-367.
•   Discusses finding two impulse sequences, separated by a minute, showing that an impulse sequence can be created, even without gunshots.

https://archive.org/stream/HouseSelectCommitteeOnAssassinations/Volume%202_djvu.txt

And finally, a link to just the Dr. Barger testimony, which includes links to the figures he presented, including the all-important Exhibit F-367, which summaries the result of the August 27 Dealey Plaza firing tests, which Mr. Griffith keeps claiming have not been conducted yet.

http://mcadams.posc.mu.edu/russ/m_j_russ/hscabarg.htm

I’ll let the other members of this forum judge if I am telling the truth or him.

At the risk of seeming unkind, I am once again led to question your reading comprehension skills. I did not say, and would never say, that the Dealey Plaza test firing had not been done by the time Barger testified on September 11. I said that the segment you quoted from Dr. Barger's testimony was the part where he was talking about BBN's preliminary analysis, which was done before the test firing.

When the BBN scientists had completed their preliminary analysis, they felt they could not proceed without test-firing data to compare to the dictabelt data. Therefore, Dr. Barger contacted HSCA chief counsel Robert Blakey and explained that BBN needed to do a test firing in Dealey Plaza in order to move forward with the dictabelt analysis. Dr. Barger submitted BBN's plan for the test firing. Blakey then asked W&A to review BBN's analysis and to review the proposed plan for the test firing. W&A agreed with the test-firing plan, and the test firing was then conducted.

Dr. Weiss, from his HSCA testimony in December 1978:

Mr. WEISS. In August of this year we examined the results of Dr. Barger's analysis up to that time, and also reviewed the plan for the reconstruction experiment to be conducted in Dallas and judged whether the experiment was necessary to be performed. We did visit Dr. Barger at his lab in Cambridge, Mass., and had a lengthy discussion with him, saw his result, and reported back to the committee that in our opinion the reconstruction experiment was not only fully justified but also necessary for the continuance of his analysis. (5 HSCA 556)

From the HSCA report:

BBN was asked to examine the channel 1 Dictabelts and the tape that was made of them to see if it could determine: (1) if they were, in fact, recorded transmissions from a motorcycle with a microphone stuck in the "on" position in Dealey Plaza; (2) if the sounds of shots had been, in fact, recorded; (3) the number of shots; (4) the time interval between the shots; (5) the location of the weapon or weapons used to fire the shots; and (6) the type of weapon or weapons used.

BBN converted the sounds on the tape into digitized waveforms and produced a visual representation of the waveforms.(11) By employing sophisticated electronic filters, BBN filtered out "repetitive noise," such as repeated firings of the pistons of the motorcycle engine.(12) It then examined the tape for "sequences of impulses" that might be significant. . . .

Six sequences of impulses that could have been caused by a noise such as gunfire were initially identified as having been transmitted over channel 1.(13). . . .

These six sequences of impulses, or impulse patterns, were subjected to preliminary screening tests to determine if any could be conclusively determined not to have been caused by gunfire during the assassination. The screening tests were designed to answer the following questions:(14). . . .  [The report then lists the six criteria, which I have quoted twice already.]

BBN next recommended that the committee conduct an acoustical reconstruction of the assassination in Dealey Plaza to determine if any of the six impulse patterns on the dispatch tape were caused by shots and, if so, if the shots were fired from the Texas School Book Depository or the grassy knoll.(16) The reconstruction would entail firing from two locations in Dealey Plaza--the depository and the knoll--at particular target locations and recording the sounds through numerous microphones. The purpose was to determine if the sequences of impluses recorded during the reconstruction would match any of those on the dispatch tape. If so, it would be possible to determine if the impulse patterns on the dispatch tape were caused by shots fired during the assassination from shooter locations in the depository and on the knoll. (HSCA Report, pp. 68-69)

Richard Trask (you know who he is, right?):

The Committee decided to give this problem over to acoustics experts. These respected acoustics scientists would analyze the nature and origin of the suspect sound impulses on Channel 1 to determine if sounds of shots had been recorded; and if so, how many, the time interval, and point of origin. In May 1978 the Committee contracted with Bolt, Beranek and Newman, Inc. [BBN], to attempt the analysis. By means of sophisticated and, to the layman, complicated scientific analysis of the recordings, chief scientist Dr. James Barger located 6 impulse sequences which could have been caused by a loud noise such as a gunshot. The Committee was urged to conduct an acoustical reconstruction of the assassination at the Dallas site. Realizing that Barger's initial findings, if true, pointed to a probable assassination conspiracy, the Committee sought an independent review of his analysis by Queen's College, New York, professor Mark Weiss and his research associate, Ernest Aschkenasy. Barger's analysis and methodology for the reconstruction were concurred by the two others, and on August 20, 1978, an elaborate test in Dealey Plaza was conducted. (Trask, Pictures of the Pain, p. 131)

The statements you keep quoting from Dr. Barger's testimony are from when he was talking about the screening tests in the preliminary analysis. BBN did not and could not analyze N-waves and muzzle blasts on the dictabelt until they had test-firing data so they could examine the N-waves and muzzle blasts from the test-firing shots and then compare those with the oscillograms and spectrograms of the suspect impulse patterns on the dictabelt, the patterns that passed all the screening tests.

Here is link to various testimonies over several days, including the September 11, 1978 testimony by Dr. Barger where he:. . . .
•   Discusses finding two impulse sequences, separated by a minute, showing that an impulse sequence can be created, even without gunshots.

Yes, and if you read his testimony with any care, you will easily see that he was talking about BBN's preliminary analysis, and that this analysis had nothing, nothing, nothing to do with checking for N-waves and muzzle blasts. In the preliminary analysis, BBN was simply looking for any sound impulses that could not be ruled out as gunfire. To do this, they used screening tests. Again, for the third time, go look at the screening criteria they used; not one of them involved checking for N-waves and muzzle blasts. The N-wave and muzzle-blast analysis came later, after they had the test-firing data, naturally enough.

If you read Barger's testimony with any care, you will also notice that when he starts talking about N-waves and muzzle blasts, he refers to graphical representations of data on the test-firing shots that were done with a Mannlicher-Carcano rifle and an M-1 rifle. But, when he is talking about the preliminary analysis, when they were doing basic screening tests to find gunfire candidates, he says nothing about N-waves and muzzle blasts.

And, again, after all the subsequent analysis that BBN and W&A did after the test firing, they determined that only the identified gunshot impulse patterns on the dictabelt contain N-waves, muzzle blasts, and muzzle-blast echoes, and, as the HSCA report notes, they recognized this was powerful evidence that the impulse patterns are assassination gunfire.

It is bad enough that you could not tell the difference between Dr. Barger's testimony and the BBN report. Such a gaffe indicates very careless, hurried reading. But it is even worse that you do not even know the basic timeline of the HSCA's acoustical research. If you are unable to grasp this basic, non-technical stuff, there is little hope that your upcoming response to the dictabelt-test firing correlations will be worth the virtual paper it's written on.