HSCA 1978 Acoustic Study by BBN – Figure 367

[Joe Elliott]

I claim that there are at least two clusters of “impulsive patterns” in the 5.5-minute span when the microphone key was stuck on for Channel 1. These two clusters were separated by a minute of time, meaning that at least one of the clusters was not formed by gunfire. The basis for this claim is the testimony that Dr. Barger gave on September 11, 1978 to the HSCA:


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.


Your claim this is irrelevant, because the first cluster could only have been created by gunfire, while the second cluster was of a totally different nature.


Question:

Can you provide any sort of support for your claim? That the second cluster was carefully analyzed and the waveforms were totally different from the waveforms in the first cluster?


As far as I can tell, the only objection that Dr. Barger had to the second cluster, was that it covered too short a time period, under 5 seconds. Not that the waveforms themselves did not look like the waveforms that could be created by gunfire, or fundamentally different than the waveforms found in the first cluster.

Don’t try your usual trick of posting links to several different websites that are each very long, and implying the answer is to be found somewhere in there. I’m looking for one website, and for you to copy and paste the short section that is relevant so anyone can do a simple text search to easily find this section, even in a very large webpage. Just give a simple short answer.

[Michael T. Griffith]

I claim that there are at least two clusters of “impulsive patterns” in the 5.5-minute span when the microphone key was stuck on for Channel 1. These two clusters were separated by a minute of time, meaning that at least one of the clusters was not formed by gunfire. The basis for this claim is the testimony that Dr. Barger gave on September 11, 1978 to the HSCA:

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.

Your claim this is irrelevant, because the first cluster could only have been created by gunfire, while the second cluster was of a totally different nature.

Question:

Can you provide any sort of support for your claim? That the second cluster was carefully analyzed and the waveforms were totally different from the waveforms in the first cluster?

As far as I can tell, the only objection that Dr. Barger had to the second cluster, was that it covered too short a time period, under 5 seconds. Not that the waveforms themselves did not look like the waveforms that could be created by gunfire, or fundamentally different than the waveforms found in the first cluster.

Whoa! I'll answer your dumb question in a second, but I must ask: What happened to all of your jibberish about N-waves supposedly being scattered "throughout the dictabelt"? Is your silence on that topic a tacit admission that the claim is erroneous? And I see you're no longer claiming that I made the false statement that the Dealey Plaza test firing had not been done by the time Dr. Barger testified. That claim was yet another one of your embarrassing gaffes caused by your poor grasp of the HSCA's acoustical analysis.

Now, as for your dumb question: First of all, some of the links I've provided answer that dumb question. Furthermore, the BBN report answers that dumb question. Dr. Thomas answers that dumb question in his book. The fact that you would even ask this dumb question shows that you still don't even know the basics about the acoustical evidence. 

Ok, I'll give you the short answer to your dumb question, and then I'll provide a quote to back up my answer.

The short answer is that, as I've told you several times now, the statement you keep quoting comes from when Barger was talking about the preliminary analysis. The second cluster, i.e., the later series of impulse events, that Dr. Barger was talking about was disqualified as gunfire in the preliminary analysis. It was disqualified because it failed to meet several of the screening criteria. It's mostly impulses of squawks caused by radios keying in.

As promised, and just to leave no room for honest, rational disputation on this issue, I am going to quote from the BBN report:

If impulse patterns similar to those occurring at the time of the assassination were to be found anywhere else during the 5-minute recording of stuck transmission, then the patterns could safely be assumed to have been caused by something other than gunfire. Thus, we examined processed waveforms for the entire segment of stuck transmission, looking for impulse patterns similar to those already identified. During the course of this examination, only one other pattern was found. It began about 30 sec after the other four patterns and was comprised mostly of impulses apparently caused by radios keying in, attempting to transmit. This sequence, which lasted for approximately 4 sec, did not resemble the earlier impulse patterns well enough to have been caused by the same source. (8 HSCA 75)

And remember that this was before they began looking at echo-delay sequences, topographic ordering of echo-pattern correlations, N-waves, muzzle blasts, muzzle-blast echoes, delay times of muzzle-blast echoes, windshield distortions, binary correlations, etc., etc.

Again, the impulse cluster you keep talking about did not even pass the initial screening tests in the preliminary analysis.

Don’t try your usual trick of posting links to several different websites that are each very long, and implying the answer is to be found somewhere in there.

Read: "Don't confuse me with links to scholarly articles that are too long for my attention span and that contain facts that I can't understand or explain."

The answers to your questions have indeed been "somewhere in there," but you either failed to notice them, did not understand them, or chose to ignore them.

I’m looking for one website, and for you to copy and paste the short section that is relevant so anyone can do a simple text search to easily find this section, even in a very large webpage. Just give a simple short answer.

"A simple short answer"?! You mean like your last several 12-15-paragraph replies? Look, it's just too bad that you, apparently/supposedly, have been unable to find answers to your questions in the links I've provided. I've answered most of your questions myself, but in some replies I've also provided links because I do not like to reinvent the wheel and because it's not my fault that you haven't done your homework.

[Joe Elliott]

The dude is assigned to the presidential motorcade and doesn't even know which channel he's on, WTF?

Well, to be fair to Officer McLain, he didn’t know 15 years later. He may very well have known which channel he was using on November 22, 1963.

[Joe Elliott]

Whoa! I'll answer your dumb question in a second, but I must ask: What happened to all of your jibberish about N-waves supposedly being scattered "throughout the dictabelt"? Is your silence on that topic a tacit admission that the claim is erroneous? And I see you're no longer claiming that I made the false statement that the Dealey Plaza test firing had not been done by the time Dr. Barger testified. That claim was yet another one of your embarrassing gaffes caused by your poor grasp of the HSCA's acoustical analysis.

I have been talking about other things. But as to the other isolated impulses, I have heard they are there, that the sound like short bursts of static, similar to the “gunfire” second, just shorter. But it has been years seen I read that so I cannot site it. But at least we do have two examples of impulse sequences that even the BBN admit to on the 5.5-minute stretch of the stuck-key transmission, which is enough.

Now, as for your dumb question: First of all, some of the links I've provided answer that dumb question. Furthermore, the BBN report answers that dumb question. Dr. Thomas answers that dumb question in his book. The fact that you would even ask this dumb question shows that you still don't even know the basics about the acoustical evidence. 

Ok, I'll give you the short answer to your dumb question, and then I'll provide a quote to back up my answer.

The short answer is that, as I've told you several times now, the statement you keep quoting comes from when Barger was talking about the preliminary analysis. The second cluster, i.e., the later series of impulse events, that Dr. Barger was talking about was disqualified as gunfire in the preliminary analysis. It was disqualified because it failed to meet several of the screening criteria. It's mostly impulses of squawks caused by radios keying in.

As promised, and just to leave no room for honest, rational disputation on this issue, I am going to quote from the BBN report:

If impulse patterns similar to those occurring at the time of the assassination were to be found anywhere else during the 5-minute recording of stuck transmission, then the patterns could safely be assumed to have been caused by something other than gunfire. Thus, we examined processed waveforms for the entire segment of stuck transmission, looking for impulse patterns similar to those already identified. During the course of this examination, only one other pattern was found. It began about 30 sec after the other four patterns and was comprised mostly of impulses apparently caused by radios keying in, attempting to transmit. This sequence, which lasted for approximately 4 sec, did not resemble the earlier impulse patterns well enough to have been caused by the same source.

No, you have still not given me a sufficient answer. This quote is insufficient. What was it about the second cluster of impulses that caused the BBN to discount it? How could they tell the first cluster was made differently, while the second could only have been made by an attempt for someone else to transmit?

The two sequences did not resemble each other well enough. In what way?

Was it because the first cluster consisted of N-waves while the second of sin-waves?
Was it because the first pattern was 10.1 seconds long and the second was only 4 seconds long?

The BBN report does not explicitly say?


And again, to stress again, the BBN report says the two sequences were different. They make no claim that an individual impulse in the first sequence was fundamentally different than an individual impulse in the second sequence. Maybe they meant to say that. But they didn’t.


And let us make the unfounded assumption for the moment that an individual impulse was different in a fundamental way from one in the second. Would that alone be enough to conclude that both impulse sequences were not caused by someone keying in? Could not someone trying to key in over a radio in a police car produce different impulse patterns than someone trying to transmit over a motorcycle radio? Did both use the same type of radio? Could the distance from the radio receiver at headquarters make a difference, like 200 yards as opposed to 10 miles?

Even if the two impulse patterns do different in some fundamental way, other than the length of the time of the segments, we can’t conclude they were not both made by attempts of someone to transmit a short message, which are commonly 4 to 10 seconds long, as can been seen throughout the Dictabelt recording.



In any case, back to the main point, It seems, for all we know, the BBN reasons for discounting the second sequence of impulses were:
•   All the shooting took place within about 10 seconds, so both sequences could not be gunfire.
•   It was believed the shooting took place a span of any least 5 seconds, so the second sequence of 4 seconds could not have been the gunfire.

As far as I can tell, there are no other reasons for dismissing this second sequence. For all we know, if the same sort of comparison was made between the impulses of this second sequence with the Dictabelt, they would have found more pairs with a correlation coefficient of 0.6, 0.7 and 0.8. As far as I can tell BBN just assumed the first sequence might have been produced by gunfire and the second by someone attempting to transmit. As far as I can tell, BBN could have just as easily have made the opposite assumption.


Again, the only reasons this report explicitly gave for rejecting the second sequence of impulses were:

•   It only covered 4 seconds.

There is nothing about the impulses in this second sequence being of a fundamental nature different than those of the first.

If there are addition reasons for rejecting this second sequence, the BBN report failed to spell them out.


So, as far as I can tell, they simply dismissed the second sequence as gunshots, because they only covered 4 seconds, and for that reason alone. Once that is assumed that, then they figured it must have been caused by something else, like someone trying to transmit a message. They may be right. But of course, maybe both sequences were caused by someone trying to transmit a message.


So, you keep complaining I keep answer for answers you already given, but I am going to continue to keep calling for answers until you can give a quality answer. Which, apparently, the BBN never provided.

[Michael T. Griffith]

I have been talking about other things. But as to the other isolated impulses, I have heard they are there, that the sound like short bursts of static, similar to the “gunfire” second, just shorter. But it has been years seen I read that so I cannot site it. But at least we do have two examples of impulse sequences that even the BBN admit to on the 5.5-minute stretch of the stuck-key transmission, which is enough.

This is idiotic stuff. You still haven't read the BBN report, the W&A report, and Thomas's book, have you?

No, you have still not given me a sufficient answer. This quote is insufficient. What was it about the second cluster of impulses that caused the BBN to discount it? How could they tell the first cluster was made differently, while the second could only have been made by an attempt for someone else to transmit?

Do I need to quote the accompanying paragraphs to establish that the context was the impulses that passed and did not pass the initial screening tests? That's the context of the BBN report's statement that I quoted:

During the course of this examination, only one other pattern was found. It began about 30 sec after the other four patterns and was comprised mostly of impulses apparently caused by radios keying in, attempting to transmit. This sequence, which lasted for approximately 4 sec, did not resemble the earlier impulse patterns well enough to have been caused by the same source.

The two sequences did not resemble each other well enough. In what way?

Because the second sequence failed several of the screening tests. That's because it was caused mostly by the squawking from radios keying in. It was not even close enough in its characteristics to have been caused by the same source as the impulse patterns that begin 2 seconds after Curry's "triple underpass" transmission and 2 seconds after Fisher's simultaneous "I'll check" crosstalk.

Was it because the first cluster consisted of N-waves while the second of sin-waves?
Was it because the first pattern was 10.1 seconds long and the second was only 4 seconds long?

If there are no N-waves and muzzle blasts and muzzle-blast echoes, it ain't gunfire, unless the gunfire was recorded when the mike was not in position to record them. If those things aren't present in the impulse sequence, and if it was recorded when the mic could record those things, then that sequence is not gunfire. Period. End of story. Rifle shots cause N-waves and muzzle blasts and muzzle-blast echoes. Nobody but nobody disputes this fact. So if an impulse pattern on a record does not contain any of these three characteristics, then it cannot be gunfire--again, with the sole caveat that of course the recording mike would have to be in a location that would enable it to record the N-waves. Why can't you grasp this simple, basic point?

The BBN report does not explicitly say?

It's pretty clear on this if you read it with your brain turned on and if you have enough intelligence to understand the English. This part of the BBN report is discussing the first screening tests. It says the 4-second impulse sequence consists mostly of radios keying in. It says the sequence "did not resemble the earlier impulse patterns well enough to have been caused by the same source." So obviously it was not even a close call.

And again, to stress again, the BBN report says the two sequences were different. They make no claim that an individual impulse in the first sequence was fundamentally different than an individual impulse in the second sequence. Maybe they meant to say that. But they didn’t.

Then you can't read. The BBN report says the second impulse sequence "did not resemble the earlier impulse patterns well enough to have been caused by the same source" because it failed to pass the initial screening tests. If you read the surrounding text, this is crystal clear. An impulse sequence had to pass all of the screening tests to warrant further analysis.

And, again, this was before they began comparing any N-wave-like and muzzle-blast-like oscillograms and/or spectrograms of the suspect impulse patterns with those of the shots from the test firing. This was also before they tested for the appropriate presence or absence of windshield distortions. This was also before they did binary correlation analysis. This was also before they tested for echo-delay correlations.

And let us make the unfounded assumption for the moment that an individual impulse was different in a fundamental way from one in the second. Would that alone be enough to conclude that both impulse sequences were not caused by someone keying in? Could not someone trying to key in over a radio in a police car produce different impulse patterns than someone trying to transmit over a motorcycle radio? Did both use the same type of radio? Could the distance from the radio receiver at headquarters make a difference, like 200 yards as opposed to 10 miles?

Even if the two impulse patterns do different in some fundamental way, other than the length of the time of the segments, we can’t conclude they were not both made by attempts of someone to transmit a short message, which are commonly 4 to 10 seconds long, as can been seen throughout the Dictabelt recording.

In any case, back to the main point, It seems, for all we know, the BBN reasons for discounting the second sequence of impulses were:
•   All the shooting took place within about 10 seconds, so both sequences could not be gunfire.
•   It was believed the shooting took place a span of any least 5 seconds, so the second sequence of 4 seconds could not have been the gunfire.

As far as I can tell, there are no other reasons for dismissing this second sequence. For all we know, if the same sort of comparison was made between the impulses of this second sequence with the Dictabelt, they would have found more pairs with a correlation coefficient of 0.6, 0.7 and 0.8. As far as I can tell BBN just assumed the first sequence might have been produced by gunfire and the second by someone attempting to transmit. As far as I can tell, BBN could have just as easily have made the opposite assumption.

Again, the only reasons this report explicitly gave for rejecting the second sequence of impulses were:

•   It only covered 4 seconds.

There is nothing about the impulses in this second sequence being of a fundamental nature different than those of the first.

If there are addition reasons for rejecting this second sequence, the BBN report failed to spell them out.

So, as far as I can tell, they simply dismissed the second sequence as gunshots, because they only covered 4 seconds, and for that reason alone. Once that is assumed that, then they figured it must have been caused by something else, like someone trying to transmit a message. They may be right. But of course, maybe both sequences were caused by someone trying to transmit a message.

So, you keep complaining I keep answer for answers you already given, but I am going to continue to keep calling for answers until you can give a quality answer. Which, apparently, the BBN never provided.

Blah, blah, blah, blah. . . .  It's a waste of time trying to reason with you because you will not deal honestly with the evidence, or else you genuinely do not have the ability to understand the evidence. You are desperately grasping onto an impulse sequence that was disqualified in the preliminary analysis, for crying out loud. The HSCA materials and Dr. Thomas spend very little time on this sequence precisely because it failed the first and easiest round of screening.

You're never going to admit anything that supports the acoustical evidence because you don't want to believe it. It's as simple as that.

[Joe Elliott]

This is idiotic stuff. You still haven't read the BBN report, the W&A report, and Thomas's book, have you?

No. The 1978 Acoustic experts failed to collect the Dictabelt recording from August 27, 1978 which would have established, or refuted:

•   The Dictabelt would have, or would not have, recorded gunshots as loud audible noises.
•   The Dictabelt would have, or would not have, recorded crowd noises, which could have been simulated.
•   Examples of just exactly what you get when a transmit button is pressed and held as if it is stuck and other motorcycle officer attempts to transmit a message, from a motorcycle and from a patrol car.

I understand W&A just looked at the so called “Grassy Knoll” shot and so studied the second set of impulse sequences less than the BBN did.

And Dr. Thomas has been dishonest about the sirens heard on the Dictabelt, implying you can hear them loudly all the way to the hospital, when in truth, you don’t hear them, then they gradually get louder, and then fade away, as if recorded from a stationary motorcycle at the Trade Mart Center. Plus, he is dishonest in making drawing of Dealey Plaza showing that Officer McLain could have been within circles with a radius of 18 feet, and so he might just miss being in the Altgens photograph, when the 1978 prediction was that a motorcycle would be found circles with a 9-foot radius. So, unless someone can explain to me that he wasn’t really being dishonest in both these cases, I’m not going to be reading any of his books anytime soon.

Maybe you can get me and others to read the BBN report if you can just provide a little real support for their claim that the second sequence of impulses was just caused by someone else trying to transmit a message, like a plot of those waveforms.

Do I need to quote the accompanying paragraphs to establish that the context was the impulses that passed and did not pass the six screening tests? That's the context of the BBN report's statement that I quoted:

No. No more quotes. Show me evidence. Show me the plots of the of the all the waveforms from the first sequence and all the waveforms from the second. So, a layman, such as myself, and others at this forum, can see the clear differences between an impulse from the first sequence and an impulse from the second.

Because the second sequence failed several of the screening tests. That's because it was caused mostly by the squawking from radios keying in. It was not even close enough in its characteristics to have been caused by the same source as the impulse patterns that begin 2 seconds after Curry's "triple underpass" transmission and 2 seconds after Fisher's simultaneous "I'll check" crosstalk.

So, there are other impulse sequences on the Dictabelt recording? Not just the two that Dr. Barger referred to?

If there are no N-waves and muzzle blasts and muzzle-blast echoes, it ain't gunfire. If those things aren't present in the impulse sequence, then that sequence is not gunfire. Period. End of story. Rifle shots cause N-waves and muzzle blasts and muzzle-blast echoes. Nobody but nobody disputes this fact. So if an impulse pattern on a record does not contain any of these three characteristics, then it cannot be gunfire. Why can't you grasp this simple, basic point?

Where is the evidence for any of this? Why didn’t BBN provide plots of the waveforms showing individual impulses from both the first and second sequence so anyone can see that they must have formed in a different matter?

It's pretty clear on this if you read it with your brain turned on and if you have enough intelligence to understand the English. This part of the BBN report is discussing the first screening tests. It says the 4-second impulse sequence consists mostly of radios keying in. It says the sequence "did not resemble the earlier impulse patterns well enough to have been caused by the same source." So obviously it was not even a close call.

Where is the evidence for this claim? Where are the plots of the waveforms from both sequences?

Then you can't read. The BBN report says the second impulse sequence "did not resemble the earlier impulse patterns well enough to have been caused by the same source" because it failed to pass the initial screening tests. If you read the surrounding text, this is crystal clear. An impulse sequence had to pass all six of the screening tests to warrant further analysis.

Yes. It failed to meet the initial screening test. The only screening test that I saw them explicitly explain was that it was only 4 seconds long and it needed to be 5 seconds long. That doesn’t prove the first sequence was caused by gunfire and the second by someone keying in. Maybe the first sequence was someone talking into their transmitter for 10 seconds and the second by someone talking for 4 seconds.



Question:

Did the BBN provide plots of all the waveforms in the first sequence?

Did the BBN provide plots of all the waveforms in the second sequence?

How many impulses were in the second sequence?

At what time, to the nearest hundredth of a second, do each of these impulses occur, so we can know their timing just as we do for all the impulses in the first sequence.

[Michael T. Griffith]

It might help to point out that after BBN did the test firing in Dealey Plaza, they were able to perform more tests to identify gunfire sounds on the dictabelt. One of those tests was the matched filter test. Importantly, they applied this test to all the impulses on the dictabelt. No sound impulses that were recorded after Curry’s “to the hospital” transmission passed the matched filter test. Five of the six suspect sound impulses did pass the test. Here is some information about when and how BBN used the matched filter technique on the dictabelt, from Dr. Barger’s HSCA testimony:

Mr. FITHIAN. And one final sort of terminology question. You used the term "match filter technique," matching filter techniques"—

Dr. BARGER. Yes.

Mr. FITHIAN [continuing]. And that means what?

Dr. BARGER. That means that you have in your--you expect to receive one of many kinds of signals. By "many kinds," I mean a signal in this case that has a series of impulses that occur in a definite sequence, like, let's say, the first one occurs at a particular time, the second one perhaps 3 milliseconds later, the third one maybe 15, the fourth one 27, the fifth one 121/z after that, and so on, a definite sequence of impulses.

We went to Dallas to find out what the sequence of impulses would be that would be generated by Dealey Plaza if a gun was fired.

Having found out what that sequence of impulses is, you then go through the tape in question and look for sequences of impulses that match it. When you find one that matches it, you say aha, at that time something occurred that generated a pattern of transient events that just matches what we did in Dealey Plaza, and when that occurs, you judge that you have made a detection. You have identified a similar source of noise. The word "matched filter" is a technically correct or often used form, and the use of the word "match" is fairly self-evident, I believe. (2 HSCA 73-74)

Dr. BARGER. There is in the field of detection theory a favorite approach called matched filtering. The matched filter is a device that is used to detect events that you have some understanding of, even though they are subaudible. Matched filters are used in radar sets commonly to detect the presence of impulsive signals in noise, even though they are not visible or audible in the raw data. There was reason to believe that applying these techniques we might be able to detect the impulsive sounds of gunfire. (2 HSCA 18)

Dr. BARGER. Then we counted the number of impulses in each pattern of impulses that we see in the waveform records of the tape and we saw there were about 10. We realized there was still a possibility that these impulsive sounds that we saw in the record of the tape were in fact caused by gunfire.

Mr. CORNWELL. At this point then you had devised six screening tests, any one of which I take it might have been sufficient to rule out these impulses as being gunshots, and they in fact passed all six tests, is that correct?

Dr. BARGER. Quite so.

Mr. CORNWELL. Now, at this point did you have any conclusions or, on the other hand, did you feel that further testing was required?

Dr. BARGER. At this point we felt we were justified in suggesting to the committee that a matched filter detection trial was warranted on the tape. As I said, the patterns that formed the basis for the match would have to be obtained by an acoustical reconstruction. The reason for suggesting the matched filter procedure for detecting the events was it is the most powerful method we know of with which to do that.

Mr. CORNWELL. How about telling us in just plain, common language what you are referring to when you say an acoustical reconstruction?

Dr. BARGER. The objective is to obtain echo patterns of the sort that I described briefly before, and the purpose for having these patterns is to become the basis of the match in the matched filter detector. In order to get these echo patterns, it was necessary to design a test that would get echo patterns that would in fact match with the events on the tape if in fact there were events on the tape that were gunfire. (2 HSCA 46-47)

And, needless to say, the matched filter test found that five of the six dictabelt impulse patterns that passed the initial screening tests contained echo patterns that matched those of shots from the test firing.

I’d like to note that the HSCA’s use of acoustical analysis to determine the existence and location of gunfire was neither novel nor based on unproven technology. Acoustical analysis was used in the Kent State shooting. As chance would have it, the lead acoustical scientist in that case was James Barger, who was also one of the HSCA acoustical experts. In the Kent State case, Barger used the same procedure that he used for the HSCA, namely, echo location based on an audio record of the incident. Barger was able to identify the physical locations of the first gunshots fired at Kent State to within 10 feet of where they were later determined to have been fired when the National Guardsmen who fired them were arrested and admitted they had fired the shots.

So no one should claim that acoustical analysis technology is unproven. The same technology has been used for many years by the Army for locating enemy gun emplacements and snipers, by the Navy to navigate underwater, and by geologists to find oil deposits.

[Joe Elliott]

It might help to point out that after BBN did the test firing in Dealey Plaza, they were able to perform more tests to identify gunfire sounds on the dictabelt. One of those tests was the matched filter test. Importantly, they applied this test to all the impulses on the dictabelt. No sound impulses that were recorded after Curry’s “to the hospital” transmission passed the matched filter test. Five of the six suspect sound impulses did pass the test. Here is some information about when and how BBN used the matched filter technique on the dictabelt, from Dr. Barger’s HSCA testimony:

No, they did not apply the “matched filter test” to all the impulses on the Dictabelt. Specifically, it was only applied to all the impulses on the first sequence of 10.1 seconds, not on the second sequence of 4.0 seconds that was recorded on the Dictabelt 30 seconds later.

The “matched filter test” was comparing the 7 impulses from the first impulse sequence, covering 10.1 seconds, with the 2,408 impulses from the 1978 test with 69 rifle shots recorded on 36 microphones.

“Five out of six did passed the “match filter test”. First of all, it was seven impulses, not six. And only four of the seven passed, that is, had a correlation coefficient of 0.8 or higher. And the four that did pass, barely passed.

But the main point is, the second sequence, the 4-second sequence, was never given the “matched filter test”. For all we know, some of the impulses in that 4.0-second sequence would have passed as well, which would have served to discredit the BBN study.

But of course, the BBN study was discredited anyway, by their own data. Check out the BBN’s Exhibit F-367 table which I have in my initial post of this thread. We don’t have a “match”, for a certain 1978 recreation shot, with both an impulse found in the Dictabelt 10.1-second and the 4.0-second sequence, because this test was never made. But we do have a couple of matches, for both the 137.70 and 145.61 Dictabelt shots, where matches of 0.8 correlation coefficient was found for a shot fired at two different targets. That shouldn’t happen. Each shot should have its own unique fingerprint. So, a correlation of 0.8 is not sufficient to say “We have a perfect match with this shot, fired from this location, at this target, recorded from this location” because they have two different shots that reach 0.8. Clearly a higher threshold than 0.8 was needed to make this determination, but the BBN could not find any.