HSCA 1978 Acoustic Study by BBN – Figure 367

[Michael T. Griffith]

Is “mostly a bunch of squawks” Dr. Barger’s description or yours? Where does Dr. Barger say, in some many words, that this particular impulse sequence, of 4-seconds, was a bunch of “squawks”, or words to that effect. And yes, he does give the opinion that this 4-second impulse sequence was caused by someone trying to key in, but where does he give evidence to support this opinion?

Please tell me you're kidding. Can you get any sillier or pettier? Have you listened to the dictabelt? I take it you've never been around radios? How would you describe the sound that is made when someone uses their radio to key in on a channel?

If it makes you happy, replace "squawks" with whatever word you would use to describe the sound that occurs when a radio keys in on a channel.

Barger didn't give "evidence" to support his "opinion"? So Barger and the other experts could not recognize the sounds of radios keying in? Seriously?

From what I have read, Dr. Barger rejects this 4-second sequence of impulses, because it was shorter than 5-seconds.

Yeah, you keep saying that, and I keep telling you that you're wrong and that you need to read all of the HSCA materials. The 4-second sequence failed two of the screening tests, not just one. It failed the duration test, and it also failed the amplitude test. Plus, the shapes of its impulses did not resemble the shapes of N-wave and muzzle blast patterns. I quote from the BBN report, and let me note that if you read the surrounding paragraphs, you will see that this paragraph is talking about the analysis that was done before the test firing was conducted:

The recorded outputs from both filters for the full 5 minutes were compared, examined, and plotted on a scale where 5 in. equals 1/10 sec. These plots revealed five impulse patterns introduced by a source other than the motorcycle. Upon closer examination, all but one of these patterns were sufficiently similar to have had the same source, and the impulses contained in these patterns appeared to have shapes similar to the expected characteristics of a shock wave and of a muzzle blast. The remaining pattern was sufficiently different in amplitude and duration as to have been caused by a different source. (8 HSCA 43)

So the impulses in the four patterns that were "sufficiently similar to have had the same source" also had shapes "similar to the expected characteristics of a shock wave and of a muzzle blast." The "remaining pattern"--the 4-second pattern--did not have the shapes of N-waves and muzzle blasts and was different from the other patterns in amplitude and duration.

So, once and for all, your 4-second impulse pattern is a dead end, a non-issue.

As for your continued polemic about F-367, I'm not going to waste time repeating why your characterization of it is misleading. Dr. Thomas spends six pages discussing the facts surrounding the 140.3 gunshot impulse (Hear No Evil, pp. 587-593). Go read it, and then come back and tell me there were valid grounds for rejecting it. 0.6 was a deliberately high threshold to eliminate as many false alarms as possible without also missing gunfire, and the 140.3 shot met that threshold.

And, yes, Blakey did pressure BBN to reject the 140.3 shot on non-acoustical grounds--again, for the third or fourth time, Dr. Barger admitted to Dr. Thomas that the 140.3 shot was rejected based on a circular argument and an "ad hoc" criterion. This is all discussed in Dr. Thomas's section on the 140.3 shot. I should add that Blakey himself admitted to Dr. Thomas that he did not want to accept the 140.3 shot because he knew he was going to take tremendous heat just for saying the dictabelt contained four gunshots, and because he feared that the fifth shot would dilute the case for four shots.

[Joe Elliott]

And, yes, Blakey did pressure BBN to reject the 140.3 shot on non-acoustical grounds--again, for the third or fourth time, Dr. Barger admitted to Dr. Thomas that the 140.3 shot was rejected based on a circular argument and an "ad hoc" criterion. This is all discussed in Dr. Thomas's section on the 140.3 shot. I should add that Blakey himself admitted to Dr. Thomas that he did not want to accept the 140.3 shot because he knew he was going to take tremendous heat just for saying the dictabelt contained four gunshots, and because he feared that the fifth shot would dilute the case for four shots.

That is just stupid. Saying there were four shots, three from the TSBD, one from the Grassy Knoll, is something Blakey can handle. But saying there were five shots, four from the TSBD, one from the Grassy Knoll, that’s going to get Blakey in too much trouble. He’ll be taken out by the men in black within the week.

As for your continued polemic about F-367, I'm not going to waste time repeating why your characterization of it is misleading. Dr. Thomas spends six pages discussing the facts surrounding the 140.3 gunshot impulse (Hear No Evil, pp. 587-593). Go read it, and then come back and tell me there were valid grounds for rejecting it. 0.6 was a deliberately high threshold to eliminate as many false alarms as possible without also missing gunfire, and the 140.3 shot met that threshold.

And, yes, Blakey did pressure BBN to reject the 140.3 shot on non-acoustical grounds--again, for the third or fourth time, Dr. Barger admitted to Dr. Thomas that the 140.3 shot was rejected based on a circular argument and an "ad hoc" criterion. This is all discussed in Dr. Thomas's section on the 140.3 shot. I should add that Blakey himself admitted to Dr. Thomas that he did not want to accept the 140.3 shot because he knew he was going to take tremendous heat just for saying the dictabelt contained four gunshots, and because he feared that the fifth shot would dilute the case for four shots.

There are clear problems with the BBN’s chart, Exhibit 367 (shown at my initial post of this thread). It shows “matches” that contradict itself. It gives “good” matches for different test shots that were either fired from a different location, recorded from a different location, or where the rifle was aimed at a different location. And this is true, even if one sticks to the highest available standard, a correlation coefficient of 0.8.

This is bad. This is not a case of: “One Match good. Two matches better. Three matches better still.”


This chart is analogous to someone who claims they have a new DNA test procedure, just as good as existing procedures, but only a tenth as expensive. When a DNA sample from a crime scene, known to have been committed by one criminal, is compared with a database of criminals, it comes up with two matches:

Mr. Jones and Mr. Smith

That’s not good. A good test should not have multiple matches, it should only have one match.

When pressed about which of them is guilty, they say Mr. Smith. Why? Because he lived one hundred miles closer to the victim.


So, getting two matches for the shot at 137.70, one for a shot aimed at Target 1, the other at Target 3, that is not good. Clearly the problem is that the threshold of 0.8 is not high enough. At least one of these tests got a high enough correlation due to luck. Perhaps both did.

If one now accepts a correlation coefficient of 0.6 as good enough, one gets into more hot water. If this is true, then we know from BBN’s Exhibit F-367 that for the second shot at 139.27, the motorcycle was at both microphone 2(6) and at microphone 3(5), a distance of over 90 feet apart. This is amazing, since one should only get a good match if motorcycle was within a few feet of the corresponding 1978 microphone.

So now the question is, where was the motorcycle that recorded shot 139.27?  120 feet behind, 210 feet behind, 250 feet behind, the limousine? Which is it? All three are good, if we accept the 0.6 threshold as good enough.


Only by insisting on a high threshold, as BBN did back in 1978, do most (but not all) of these problems disappear.



Question 1:

If the case for the shot at 140.32 is just as strong as the case for the other four shots, why was it given a correlation coefficient of only 0.6 while the other four a correlation of 0.8.

Did Dr. Barger “fake” his data by changing a 0.8 measurement to a 0.6 measurement?

Yes or No?

Don’t dodge the question. Why was this shot given a correlation of only 0.6? Was this an honest measurement? Or was the data doctored by Dr. Barger.

Again, I’m not asking why this shot was rejected by the BBN in 1978. I am asking why the correlation coefficient was only 0.6?

[Michael T. Griffith]

Oh, my! I see that you snipped the part of my reply where I proved that the 4-second impulse pattern is a dead end, a non-issue. You've been droning on and on about that pattern and about how it supposedly proved that the HSCA experts ignored other valid gunshot-like patterns on the dictabelt. And I've been telling you over and over that the pattern was rejected because it failed more than one of the initial screening tests in the preliminary analysis, but you kept saying, "Gee, as far I can tell, it was only rejected because it wasn't long enough." But now that I have proved from the BBN report that the pattern failed two of the five screening tests and that it contains no N-wave and muzzle-blast patterns, you go silent on the subject.

That is just stupid. Saying there were four shots, three from the TSBD, one from the Grassy Knoll, is something Blakey can handle. But saying there were five shots, four from the TSBD, one from the Grassy Knoll, that’s going to get Blakey in too much trouble. He’ll be taken out by the men in black within the week.

This is not a serious answer. Five shots is 25% more than four shots and 33% more than three shots. Plus, you omitted the fact that acknowledging the fifth shot would have also required admitting that there was another gunman firing from behind. So it is not at all "just stupid" that Blakey did not want to admit that five shots were fired. It was wrong and misleading, but it was not "stupid."

This is similar to your silly answer when I made the factual point that the NRC panel had ample funding to conduct the same tests on the 4-second pattern that the HSCA did on the gunshot impulse patterns. Doing those tests would not have cost a lot of money, and the NRC panel had all the time in the world to get them done. But, they declined to do so. Why? Probably because they knew it would be a waste of time, because they, unlike you, had at least read the HSCA materials, and so they knew that the 4-second pattern had been rejected on entirely valid grounds.

There are clear problems with the BBN’s chart, Exhibit 367 (shown at my initial post of this thread). [MORE MISLEADING, CONFUSED DRIVEL SNIPPED]

Nope, I'm not gonna waste any more time dealing with your nonsense about this. We have already seen, repeatedly, that you have no business even talking about this stuff in the first place.

The only "clear problems" involve your inability to understand what you read about the acoustical evidence and/or your refusal to deal with it honestly and objectively. You didn't know that Bowles' transcript is bogus. You couldn't tell the difference between Barger's HSCA testimony and the BBN report (a true head-scratcher). You spent days and days repeating your bogus, clueless claim that the HSCA experts found N-waves "scattered throughout the dictabelt." You spent days and days claiming that the 4-second pattern was rejected only because it wasn't long enough. You didn't know that BBN did the initial screening tests before they did the Dealey Plaza test firing. Just in the last two days you repeated the long-debunked siren and Trade Mart arguments. The last time I checked, you were still peddling the bogus argument that Decker's "hold everything" crosstalk is the determinative time indicator, even though it is the most out-of-sync of all the crosstalk episodes, and even though five other time indicators contradict it. Heck, as of yesterday, you didn't even know when BBN said the first and last shots were fired (because you were using Bowles' bogus transcript). And on and on I could go.   

And, I am still waiting for you to address the core of the acoustical evidence. In your thread in which you pretend to refute the acoustical evidence (your "Probably Bogus Correlation" thread), incredibly (but not at all surprisingly), you do not deal with any of this evidence. None of it. 

For the sake of other readers, here is the core of the acoustical evidence:

* At least four sets of gunshot echo patterns unique to Dealey Plaza occur on the dictabelt.

* Those echo patterns occur in the correct topographic order, which is an amazing correlation all by itself.

* The echo patterns indicate that the microphone (i.e., the motorcycle with the stuck mike) was moving at the same speed at which we know the motorcade was moving.

* The dictabelt contains N-waves from supersonic rifle fire, and those N-waves occur only among the identified gunshot impulse patterns.

* The dictabelt not only contains N-waves but it also contains muzzle blasts and muzzle-blast echoes, and those N-waves, muzzle blasts, and muzzle-blast echoes occur in the correct order and interval.

* Windshield distortions occur in the dictabelt's gunshot impulse patterns when they should and do not occur when they should not.

[Joe Elliott]

The Multiple Matches Problem


This post is just focused on one question. If a scientific procedure finds multiple matches, when it should only find one match, is that a good thing?


For instance, let’s say we have an existing DNA testing procedure, Procedure A, that collects DNA from a crime scene, and compares it to a database of DNA of suspected criminals and looks for a match. And this procedure has proven good. Now, there is a new proposed Procedure B, that would be half as expensive. So, to test it, we take the DNA from known crime samples, each of which only contained DNA from one man (as proven by Procedure A) and try Procedure B on it. Procedure B may report:

Scenario 1: Only one match found, of a Mr. Jones.

Scenario 2: Two matches found, of a Mr. Jones and a Mr. Smith.

With this information alone, which scenario would bolster Procedure B best?

Clearly, it is scenario 1. Of course, to be fully bolster, we would have to check to see if Mr. Jones was the same match found when Procedure A was used.

But if it turned out that scenario 2 is what played out, that is bad for Procedure B. One of those results has to be false. We must have at least one false positive. And that is bad.

And if we had not 2 matches but 10 matches, that would be very bad. It would mean, if this was the typical result over many test samples, at least 9 in 10 of all matches are false positive. Maybe 10 of 10. Switching to Procedure B would clearly be unacceptable.

Clearly getting multiple matches is bad, because we have discovered that the proposed procedure generates false positives. That is never good.


We have essentially the same problem with the BBN tests of 1978. Looking at BBN’s Exhibit F-367, if we use the standard that 0.6 is good enough to be considered a match, then the results for the sound impulse at 145.15, we get a match for the following shots:

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)
L	145.15	304	313	3 ( 4 )	KNOLL	3	0.8	Strong
M	145.15	304	313	3 ( 7 )	TSBD*	4	0.7		Fluke
N	145.15	304	313	3 ( 8 )	TSBD	2	0.7		Fluke

So, we learn from this, that at 145.15, timed to the nearest one hundredth of a second, there was a shot from the Grassy Knoll and a shot from the TSBD. Actually, it appears there were three shots, two shots from the TSBD aimed at Target 2 and Target 4 and one shot from the Grassy Knoll fired at Target 3.

This is bad. We have at least two false positives. It means that there is at least a 2 in 3 chance that an acoustic match is a false positive.



Questions for Mr. Griffith, or anyone else:

Question 1:

Why would find a match for a shot at 145.15 for:

A shot from the Grassy Knoll at Target 3, recorded near 3 ( 4 )
A shot from the TSBD at Target 4, recorded near 3 ( 7 )
A shot from the TSBD at Target 2, recorded near 3 (  8 )

Be considered a superior result to only finding one match:

A shot from the Grassy Knoll at Target 3, recorded near 3 ( 4 )


Question 2:

Is finding multiple matches a good thing or a bad thing, when looking for matches? For both DNA and Acoustic tests on just one shot?


Question 3:

Do you deny that the BBN’s Exhibit F-367 generated false positives?


Question 4:

Is the correlation coefficient for the shot at 140.32 of 6 an honest result? Or did Robert Blakey pressure Dr. Barger to falsify the data that he reported to the BBN?


Question 5:

If Dr. Barger did not falsify his data, why shouldn’t the low correlation coefficient disqualify the shot at 140.32?



And indeed, there are many other several problems with the BBN data. I just used the sound impulse at 145.15 as one example.

Now, to be fair, most of these problems disappear if one demands a higher standard. If one says a correlation coefficient of 0.6, or even 0.7 is not good enough to be considered a match. But then we have to throw out the alleged fifth shot of Dr. Thomas because we have to be logically consistent. We can’t say a correlation coefficient of 0.6 is considered good enough to consider 140.32 to be Dr. Thomas’s fifth shot, while at the same time the stronger correlation coefficient of 0.7 to be considered not good enough for the shot 145.15.

And, I should stress, that adopting the strict 0.8 standard causes most “Multiple Matches” problems to disappear, but not all of them. That still leaves us with 6 matches for the 4 shots and so at least two of them have to be false positives.


Will Mr. Griffith dodge these 5 simple questions? Stay tuned to find out.

[Joe Elliott]

I make the following post reluctantly, because it may give Mr. Griffith a chance to dodge my five simple questions my “Multiple Matches Problem” post I just made. But I am making it so he can’t say I dodge his questions.

Oh, my! I see that you snipped the part of my reply where I proved that the 4-second impulse pattern is a dead end, a non-issue. You've been droning on and on about that pattern and about how it supposedly proved that the HSCA experts ignored other valid gunshot-like patterns on the dictabelt. And I've been telling you over and over that the pattern was rejected because it failed more than one of the initial screening tests in the preliminary analysis, but you kept saying, "Gee, as far I can tell, it was only rejected because it wasn't long enough." But now that I have proved from the BBN report that the pattern failed two of the five screening tests and that it contains no N-wave and muzzle-blast patterns, you go silent on the subject.

I stopped talking about it because it was clear we were making no progress on it.

You talk of this 4-second impulse sequence as being nothing like the 10.1-second impulse sequence.

You told me:

The 4-second sequence failed two of the screening tests, not just one. It failed the duration test, and it also failed the amplitude test.

Well, that sounds pretty definitive. I would accept a quote like that. Except there is one problem. That is not a quote from Dr. Barger. That is a quote from you.

The quote you from the BBN report you did supply:

The recorded outputs from both filters for the full 5 minutes were compared, examined, and plotted on a scale where 5 in. equals 1/10 sec. These plots revealed five impulse patterns introduced by a source other than the motorcycle. Upon closer examination, all but one of these patterns were sufficiently similar to have had the same source, and the impulses contained in these patterns appeared to have shapes similar to the expected characteristics of a shock wave and of a muzzle blast. The remaining pattern was sufficiently different in amplitude and duration as to have been caused by a different source. (8 HSCA 43)

This quote does not seem to be talking about the 4.0-second impulse sequence. Only the 10.1-second impulse sequence. What’s more, it seems to be saying that of the 5 impulses of interest, one of them, I assume 140.32, did not have the expected characteristics of a shock wave. So, they seem to be saying four of them are good, which I assume are 137.70, 139.27, 145.15 and 146.30 looked good to them. The fifth pattern, again, I assume, 140.32, had “sufficiently different amplitude and duration” to have been caused by a different source, something other than gunfire. And the impulse at 140.32 was, of course, the impulse than only had a correlation coefficient of 0.6, that Dr. Thomas insisted was the fifth shot.

So. it appears it is Dr. Thomas’s 140.32 “shot” that is “sufficiently different amplitude and duration” to be considered by the BBN, in 1978, to be a non-gunshot.

So, the quote you gave us, not only fails to contain any evidence discredit the 4.0-second impulse sequence, it seems to discredit the fifth shot that Dr. Thomas advocates.


Now, I should mention, I am not an expert on this acoustic evidence. So, I don’t know if the 4-second impulse sequence is similar to the 10.1-second sequence that the BBN focused on as containing the “gunshots”. But so far, Mr. Griffith has not provided quotes and links to show that BBN demonstrated it. All I have seen are quotes from Mr. Griffith (failed the amplitude test) seem to come from Mr. Griffith, not from Dr. Barger of the BBN. All I get from Dr. Barger is that the 4-second impulse sequence is too short to be the gunshots which were known to have lasted over 5 seconds. And that he stated it is probably caused by someone trying to transmit a brief message. But Dr Barger did not provide any technical details as to how he could tell. Were the amplitudes of these impulses too low? Mr. Griffith has not yet produced the telling quote from any of his statements or reports.

This is not a serious answer. Five shots is 25% more than four shots and 33% more than three shots. Plus, you omitted the fact that acknowledging the fifth shot would have also required admitting that there was another gunman firing from behind. So it is not at all "just stupid" that Blakey did not want to admit that five shots were fired. It was wrong and misleading, but it was not "stupid."

Blakey is willing to say there was a second gunman firing from the grassy knoll. But not that there was a third gunman who, like the first one, was firing from behind. That still makes no sense. That still makes Robert Blakely sound stupid, anyway you spin it.

This is similar to your silly answer when I made the factual point that the NRC panel had ample funding to conduct the same tests on the 4-second pattern that the HSCA did on the gunshot impulse patterns. Doing those tests would not have cost a lot of money, and the NRC panel had all the time in the world to get them done. But, they declined to do so. Why? Probably because they knew it would be a waste of time, because they, unlike you, had at least read the HSCA materials, and so they knew that the 4-second pattern had been rejected on entirely valid grounds.

Probably the 4-second impulse sequence was rejected because of the 15-day time limit they had to prepare for their September 11, 1978 report. And, perhaps, on the subconscious level, because they didn’t want to find a second cluster of shots, because that would discredit their first cluster.



But we are getting off on all sorts of tangents. Please first respond to my previous post, on the “Multiple Matches Problem”. That addresses the heart of my arguments on how BBN’s Exhibit F-367 does not support their contention that four shots were detected.

The worst result would be to find no matches.
The best result would be to find exactly 4 matches for 4 of the impulses.
Not the worst result but a pretty bad result is to find 6 matches for these 4 impulses, showing “False Positives” do occur.

[John Iacoletti]

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.

Can you provide a link to the audio recording where you are hearing this?

[Joe Elliott]

Can you provide a link to the audio recording where you are hearing this?

https://mcadams.posc.mu.edu/dpdtapes/

It is a 2:41 (two minutes, forty one seconds) recording at around 12:30.

Click on the little “speaker” and it may say you need to download Realplayer, which I did. It was fairly straight forward. I would prefer it was on youtube.

But yes, around 1:20 into the 2:41 recording, the sirens start up, build up and fade away by 1:57. I hear no more sirens from then on and the recording goes about another 44 seconds.