The HSCA Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination

[Joe Elliott]

That is [I guess] agreement that it was another 'remarkable coincidence'. To quote your previous statement...."What are the odds"?   Really? I would like to see some documentation of this.
I believe this acoustical jive is a waste of web space so if you don't reply...no loss of skin.

If there are no compelling reasons for the conspirators to shut down Channel 1 for about 5.5 minutes, and only about the first 3 minutes after the assassination, then, yes, I think this should be looked at as a coincidence.

[Joe Elliott]

Remember, the BBN’s claim that they found gunshots recorded does not rest on them finding sound impulses on the recording. There are sound impulses throughout the recording. This claim solely rests on the correlations found between their 1978 firing tests and the 1963 Dictabelt recording. So, their claim rests on the strength of Exhibit F-367, a table of all found correlations. Do these correlations seem good? Do they contradict themselves? Do they make sense?



How to Analyze Data. How to recognize random data.


Let’s say the BBN analyzed all the found correlations and produced a table of them and ended up something like this:

********** False Table used only to make a point **********

Shot 1:          from-TSBD          fired-at-Target-1          correlation:9
Shot 1:          from-KNOLL          fired-at-Target-3          correlation:6
Shot 1:          from-TSBD          fired-at-Target-3          correlation:7

Shot 2:          from-TSBD          fired-at-Target-1          correlation:7
Shot 2:          from-KNOLL          fired-at-Target-2          correlation:9

We have correlations that contradict each other. We find correlations that match the first shot with a test shot from the TSBD and the KNOLL. Does this mean the data is bad? That we may be looking at random data?

No necessarily. It may mean we have set our correlation threshold too low. Allowing us to find some correlations that are real, but also others that are not, just due to a fluke. Setting the correlation threshold too low collects the good correlations but will also collect the false correlations. So, the next thing to do is select a higher correlation, like 9, and see what that gives us:

********** False Table used only to make a point **********

Shot 1:          from-TSBD          fired-at-Target-1          correlation:9

Shot 2:          from-KNOLL          fired-at-Target-2          correlation:9

This is much better. We don’t have any correlations that contradict each other. If we had such a table for 4 shots, and they were consistent with BOTH the location of the microphone and the location of the target, then we may have good data. It would meet the minimum qualifications.


For the real BBN data from Exhibit F-367 we have correlations that contradict each other. For 3 of the 5 shots, correlations are found for both a shot from the TSBD and a shot from the Grassy Knoll. Clearly, we have the correlation threshold set too low. The only way to eliminate the contradictions is to raise the threshold from 6 to 8. If this is done, we get:

********** The real data, with the correlation threshold set at 8 **********

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)
B	137.70	168	176	2 ( 5 )	TSBD*	1	0.8	Strong
D	137.70	168	176	2 ( 6 )	TSBD	3	0.8	Strong	Fluke
G	139.27	196	205	2 ( 6 )	TSBD*	3	0.8	Strong
L	145.15	304	313	3 ( 4 )	KNOLL	3	0.8	Strong
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

First of all, it was necessary to eliminate the Dr. Thomas shot. The problem was not that it only had one correlation to support it. That was actually a good thing. The problem was its correlation was too low, at 6. It should have a stronger correlation of 8, like all our remaining strong candidates

But even these ‘strong’ candidates have problems.

For the first shot, we have a contradiction. We found correlations for both a shot at Target 1 and Target 3. Those targets are over one hundred feet apart. And only a result of Target 1 makes sense for such an early shot. In any case, a correlation of 8 is still not high enough to eliminate all the random correlations.

Also, for the first shot, if one argues the waveform would be similar for both Target 1 and 3, why did the BBN test firing at different targets? Why not just use the same target if the target location makes little or no difference? Clearly, they thought that it would make a difference. And why didn’t they get a strong correlation for Target 2 when it was tried. Strong correlation for Targets 1 and 3, but not for Target 2 which was in between? It looks like random results.


For the second shot, we have no contradictions. We found one correlation which is good. Ideal really, But the correlation found is for Target 3. It should have been found for only Target 1 or 2, or both, since the limousine would have been between both targets. But not at Target 3. Why would they get a strong correlation for Target 3 but not for Target 1 or 2? It looks like we got another random match. A correlation of 8 is still not high enough to eliminate all the random correlations.

For the third shot, no problem. Only one correlation found, which is ideal. A shot at Target 3, which is good, right where the limousine should be. If only the other shots had no clearly random results.

For the fourth shot, we have contradictions. Correlation with both Target 3 and 4, which are 240 feet apart. We should only find a correlation for Target 3. Again, a correlation of 8 is still not high enough to eliminate all the random correlations.


At this stage we should try setting the correlation threshold higher. But we can’t. The highest correlation in the data is 0.8. If we set it any higher, we have no more correlations.


This data looks like random data, particularly with the correlation threshold set at 6.

The Target locations seem random and do not track the real limousine location. Only 4 of 15 correlations give good Target locations, which is no better than random luck.

The shooter locations contradict themselves, with 3 of the 5 shots matching test shots from both the TSBD and the Grassy Knoll. In the 1978 12 test shots, 67 percent of the shots came from the TSBD and a similar 80 percent of the correlations were from the TSBD. This again looks like it could be random data.

Only the motorcycle location seems good, if the data is cherry-picked. But this may also be a factor of the BBN only checking the areas where the motorcycle could be, if travelling at a steady 11 mph. Naturally, any correlation found would match that of a motorcycle moving at a steady 11 mph.

If the data looks random, that is a fatal flaw. Writing up a bunch of words like the BBN did in their report is like putting lipstick on a pig. The BBN case stands or falls with F-367. And it falls.


Mr. Griffith will try to draw the readers attention away from BBN’s Exhibit F-367. Or if he does deal with it, he will only want to discuss the motorcycle position correlation, which may be a result of which data the BBN decided to analyze. He won’t want to talk about the correlations dealing with the shooter location or the Target location. And not discuss why a correlation of only 6, the Dr. Thomas shot, should be taken seriously.

Let’s see if he can use Table F-367 to defend Table F-367.

[Michael T. Griffith]

In my previous reply, I explained the timeline and nature of the HSCA acoustical analysis. However, I purposely did not go into much detail on the grassy knoll shot, because that would have made the reply about 50% longer, and it was already long enough. When you understand how Weiss and Aschkenasy (WA) confirmed the grassy knoll shot, you more fully understand the powerful nature of the acoustical evidence.

* The grassy knoll shot is the 145.15 shot, the third of the four shots that the HSCA acknowledged on the dictabelt recording. The BBN scientists noted that this was shot was aimed at JFK when the limousine was “near the limousine position seen in frame 313” (8 HSCA 6).

* The main reason that WA were asked to review the BBN analysis was that BBN said the grassy knoll shot had a certainty factor of only 50%. Everyone recognized that if the 145.15 shot was confirmed to be a shot from the grassy knoll, this would automatically prove that more than one gunman fired at JFK, since no one doubted that at least one shot was fired from behind, and since the sixth-floor gunman could not have fired a shot from the grassy knoll.

BBN said the three other shots had much higher certainty factors:

1st shot: 88% (based on three matches)
2nd shot: 88% (based on three matches)
4th shot: 75% (based on two matches)

* The third shot had a 50% certainty factor because it matched one test-firing shot from the grassy knoll but matched two test-firing shots from the TSBD. The grassy knoll match had a correlation coefficient of 0.8, a very high coefficient, whereas the two TSBD matches had a correlation coefficient of 0.7. Only five other matches of the 15 matches (really correlations) had a coefficient of 0.8. Based on this fact and on other factors, the BBN scientists concluded that the third shot came from the grassy knoll, but they knew that a more-refined analysis was needed to confirm this and to prove that the two TSBD matches were false matches.

The BBN scientists knew that the locations of the microphones in the test-firing caused false alarms/false matches because they did not know the exact location of the motorcycle in a given 18-foot interval:

The correlation detector produced several false alarms that could be identified as such. These false alarms are spurious matches caused by uncertainty of the exact motorcycle position with respect to the known positions of microphones used in the reconstruction test. . . . (8 HSCA 7)

The BBN scientists suspected that if they had used more microphones so that the microphones had been closer to each other, the two TSBD matches on the third shot would not have occurred.

* WA realized that the problem was that the microphones in the test firing were spaced 18 feet apart. The 18-foot spacing was the reason that BBN applied a 6-millisecond acceptance window when determining matches, since, as BBN explained, they could not be certain where the motorcycle was in a given 18-foot interval:

Because of the spacing of the microphones and lack of knowledge of the precise position of the motorcycle within the motorcade, it was fudged that the motorcycle would, in the worst case, have been no more than 18 ft away from a microphone location. The most likely separations were accounted for . . . by the establishing of a ±6-msec acceptance window for matching echo and impulse patterns. (8 HSCA 97)

* As WA explained in their testimony, they did not need to do another test firing in Dealey Plaza to solve the microphone-spacing problem. They knew they could do a computerized sonar analysis that would duplicate the conditions of closer microphone spacing--1 foot apart instead of 18 feet apart--and the resulting echo patterns. They wrote a sonar analysis program that simulated an echo pattern for 180 locations surrounding the location of the test microphone that gave the best match for the third dictabelt impulse pattern, i.e., the grassy knoll shot.

WA had written similar sonar analysis programs for the U.S. Navy—that was one of the reasons the Acoustical Society of America recommended them to the HSCA.

* Significantly, the sonar analysis enabled WA to reduce the acceptance window for a match from 6 milliseconds down to 1 millisecond, a 500% narrower window, which vastly reduced the possibility of a false match. 1 millisecond is one one-thousandth of a second. To be counted as a match, a dictabelt impulse and a test-shot echo pattern had to correspond to each other within the incredibly short timeframe of 1 millisecond.

WA also applied a noise threshold to further distinguish between non-gunfire noise and gunfire impulses.

* When WA conducted the solar analysis, they found that the dictabelt grassy knoll shot was a nearly perfect match for a test shot from the grassy knoll, which was fired from a position 8 feet west of the corner of the picket fence on the grassy knoll.

In the first sonar analysis comparison, done without the noise threshold, WA found that when the muzzle blast of the test shot was aligned with the first large impulse of the 145.15 shot—the grassy knoll shot—all 26 echoes of the test shot occurred within 1 millisecond of a corresponding impulse of the 145.15 shot.

In the second sonar analysis comparison, WA found that when they applied the noise threshold, the grassy knoll shot had 14 large impulses compared to the 12 large impulses of the test-shot pattern. Crucially, 10 of the 12 impulses in the test shot matched impulses in the grassy knoll shot to within 1 millisecond. This is an astounding correlation. Dr. Weiss explained:

Now we didn't want to include anything that might be noise in this comparison; we wanted to deal only with things of which we could be reasonably certain. So we excluded from the consideration anything which was at the noise level itself. If we knew it was below that level, then it was more probably noise than anything else, we excluded it. We wanted to know: do those things that excessed this noise level match? Well, if so, how many are there, how many do we expect to find, and how many are matched?

The answer to those three points is that there are a total of some 14 of these greater-than-noise-level peaks observed; there are a total of 10 of them that, in fact, correspond very closely to echo paths that we have been able to predict [in the simulated echo patterns].

Now our predictions also show that we should have had 12 larger-than-noise-level peaks present; but if you take these numbers and put it in an equation or formula known as the binary correlation formula, you get a number, known as a binary correlation coefficient, of .77, which says, in effect, that this pattern matches, is matched by a corresponding pattern of strong echoes with a coefficient of .77.

If you take that now and you say, well, what is the probability that this is noise, that it is just an accident that these impulses happened to fall into this sequence of spacings, the answer that you get then is that the probability that this is noise is less than 5 percent. (5 HSCA 570)

* Dr. Barger explained the importance of the WA analysis:

Mr. WOLF . In your testimony on September 11, addressing particularly the third impulse in the Dallas Police dispatch tape, you stated that the probability of this being a shot from the grassy knoll was 50-50. Professor Weiss and Mr. Aschkenasy, today, whose testimony you heard, stated that the probability of this being a shot from the grassy knoll was 95 percent or better. You have reviewed the work of Professor Weiss and Mr. Aschkenasy. Do you agree with their assessment?

Dr. BARGER. Yes; once we checked their procedures, their parameters and their echo-producing objects, we received from them the results of their match. Drs. Kalikow, Rhyne, and Mr. Schmidt and I, at Bolt, Beranek, and Newman, reviewed their results, and we concluded that they had successfully achieved a match having a correlation coefficient of .77, and you remember that was the number I was using of goodness of match. We also found that they had done this with only a plus or minus one one-thousandth of a second  error for each match, whereas we had used a plus or minus six one-thousandths of a second error window, if you will, or acceptance window as Professor Weiss called it, in order to achieve our matches.

Now, the reason that we used the large acceptance window of six one-thousandths of a second was because we didn't know, as I said, exactly where the motorcycle was. The reason they were able to lower theirs to one one-thousandth of a second was because they found exactly where it was by the procedure they described this morning. The effect of reducing this acceptance window is to greatly reduce the likelihood that noise bursts that occur could mimic the fingerprint of a shot from any place and received at that microphone. It reduces it very substantially. In other words, in the terminology that I used last time, their ability to achieve this match within plus or minus one one-thousandth of 1 second reduces the false alarm rate substantially. In other words, we had a large false alarm rate because we had a large acceptance window because we didn't know exactly where the motorcycle was. That gave us a large false alarm rate. They corrected that problem by lowering the acceptance window.

There is another feature of that score besides the acceptance window that is important. That is the value of the correlation coefficient achieved. As I said, we would not accept as a potential match any correlation coefficient that was less than one-half. But we didn't require it to be one, either, which is what it would be if there was no noise. Noise is the thing that causes the correlation coefficient to be less than one. Noise is on the Dallas Police recording.

Professors Weiss and Aschkenasy did nothing to reduce the noise, so I would not have expected they would have increased the correlation coefficient. In fact, they accepted more noise than we did, and that could have affected the correlation coefficient, which should have gone down. So their correlation coefficient, while high, was not unity. On the other hand, the false alarm rate one would expect from their match, which was so tight, this would make the likelihood of random noise bursts to fit all 10 of those to within plus or minus one one-thousandth very small.

Mr. WOLF. Your ability to state with 95-percent certainty, now, what was only a 50-50-percent probability in September was, in essence, due to the narrowing of the match time from six one-thousandths of a second to one one-thousandth of a second. Is that, in essence, correct?

Dr. BARGER. Yes, sir. After looking at what they had done, and the fact they had maintained a high correlation coefficient while reducing the acceptance window, resulted in our independent calculation of the expectancy that they could have achieved the match they got only 5 percent of the time by random if it had just been noise on the tape and not a gunshot from that place. That is why we stated independently, although their number was quite similar to ours, that we felt that the likelihood of there having been a gun shot from that knoll and received at that point now to be about 95 percent or possibly better. (5 HSCA 673-674)

* Actually, due to the fact that the two groups of HSCA acoustical experts worked separately, a math error arose in the calculation of the odds relating to the grassy knoll shot. The probability that the grassy knoll shot was the result of random noise was computed to be less than 5%, or less than 1 in 20, based mainly on a miscalculation of the value of p in the formula. The actual odds are even lower than WA calculated. Dr. Donald Thomas has demonstrated that they are actually only 1 in 100,000, or 100,000 to 1 against (http://jfklancer.com/pdf/Thomas.pdf). Put into percentage terms, the probability that chance produced the grassy knoll shot is 0.001%. To put it another way, the probability that the grassy knoll shot is a gunshot is 99.999%.

Interestingly, in their report, WA pointed out that they had been conservative in calculating the odds that chance had produced the matches between the grassy knoll shot's impulses and the test shot's echo patterns, and that the odds that chance had caused such a high degree of correlation were "considerably less than 5 percent":

The high degree of correlation between the impulse and echo sequences does not preclude the possibility that the impulses were not the sounds of a gunshot. It is conceivable that a sequence of impulse sounds, derived from non-gunshot sources, was generated with time spacings that, by chance, corresponded within one one-thousandth of a second to those of echoes of a gunshot fired from the grassy knoll. However, the probability of such a chance occurrence is about 5 percent. This calculation represents a highly conservative point of view, since it assumes that impulses can occur only in the two intervals in which echoes were observed to occur, these being the echo-delay range from 0 to 85 milliseconds and the range from 275 to 370 milliseconds. However, if the impulses in the DPD recording were not the echoes of a gunshot, they could also have occurred in the 190-millisecond timespan that separated these two intervals. Taking this timespan into account, the probability becomes considerably less than 5 percent that the match between the recorded impulses and the predicted echoes occurred by chance. (8 HSCA 32)

* Revealingly, the NRC panel recognized that WA had assigned the wrong value for p in their calculations; however, the panel not only failed to tell their readers that WA had overestimated the odds that the grassy knoll shot was random noise, but they used erroneous assumptions in their own calculations to make it seem like there was a 22% chance that the grassy knoll shot was random noise.

Yes, in so doing, the NRC panel was admitting there was a 78% chance that the grassy knoll shot was a gunshot, but 78% is quite a bit lower than 95%+, and far lower than 99.999%.

[Paul May]

In my previous reply, I explained the timeline and nature of the HSCA acoustical analysis. However, I purposely did not go into much detail on the grassy knoll shot, because that would have made the reply about 50% longer, and it was already long enough. When you understand how Weiss and Aschkenasy (WA) confirmed the grassy knoll shot, you more fully understand the powerful nature of the acoustical evidence.

* The grassy knoll shot is the 145.15 shot, the third of the four shots that the HSCA acknowledged on the dictabelt recording. The BBN scientists noted that this was shot was aimed at JFK when the limousine was “near the limousine position seen in frame 313” (8 HSCA 6).

* The main reason that WA were asked to review the BBN analysis was that BBN said the grassy knoll shot had a certainty factor of only 50%. Everyone recognized that if the 145.15 shot was confirmed to be a shot from the grassy knoll, this would automatically prove that more than one gunman fired at JFK, since no one doubted that at least one shot was fired from behind, and since the sixth-floor gunman could not have fired a shot from the grassy knoll.

BBN said the three other shots had much higher certainty factors:

1st shot: 88% (based on three matches)
2nd shot: 88% (based on three matches)
4th shot: 75% (based on two matches)

* The third shot had a 50% certainty factor because it matched one test-firing shot from the grassy knoll but matched two test-firing shots from the TSBD. The grassy knoll match had a correlation coefficient of 0.8, a very high coefficient, whereas the two TSBD matches had a correlation coefficient of 0.7. Only five other matches of the 15 matches (really correlations) had a coefficient of 0.8. Based on this fact and on other factors, the BBN scientists concluded that the third shot came from the grassy knoll, but they knew that a more-refined analysis was needed to confirm this and to prove that the two TSBD matches were false matches.

The BBN scientists knew that the locations of the microphones in the test-firing caused false alarms/false matches because they did not know the exact location of the motorcycle in a given 18-foot interval:

The BBN scientists suspected that if they had used more microphones so that the microphones had been closer to each other, the two TSBD matches on the third shot would not have occurred.

* WA realized that the problem was that the microphones in the test firing were spaced 18 feet apart. The 18-foot spacing was the reason that BBN applied a 6-millisecond acceptance window when determining matches, since, as BBN explained, they could not be certain where the motorcycle was in a given 18-foot interval:

* As WA explained in their testimony, they did not need to do another test firing in Dealey Plaza to solve the microphone-spacing problem. They knew they could do a computerized sonar analysis that would duplicate the conditions of closer microphone spacing--1 foot apart instead of 18 feet apart--and the resulting echo patterns. They wrote a sonar analysis program that simulated an echo pattern for 180 locations surrounding the location of the test microphone that gave the best match for the third dictabelt impulse pattern, i.e., the grassy knoll shot.

WA had written similar sonar analysis programs for the U.S. Navy—that was one of the reasons the Acoustical Society of America recommended them to the HSCA.

* Significantly, the sonar analysis enabled WA to reduce the acceptance window for a match from 6 milliseconds down to 1 millisecond, a 500% narrower window, which vastly reduced the possibility of a false match. 1 millisecond is one one-thousandth of a second. To be counted as a match, a dictabelt impulse and a test-shot echo pattern had to correspond to each other within the incredibly short timeframe of 1 millisecond.

WA also applied a noise threshold to further distinguish between non-gunfire noise and gunfire impulses.

* When WA conducted the solar analysis, they found that the dictabelt grassy knoll shot was a nearly perfect match for a test shot from the grassy knoll, which was fired from a position 8 feet west of the corner of the picket fence on the grassy knoll.

In the first sonar analysis comparison, done without the noise threshold, WA found that when the muzzle blast of the test shot was aligned with the first large impulse of the 145.15 shot—the grassy knoll shot—all 26 echoes of the test shot occurred within 1 millisecond of a corresponding impulse of the 145.15 shot.

In the second sonar analysis comparison, WA found that when they applied the noise threshold, the grassy knoll shot had 14 large impulses compared to the 12 large impulses of the test-shot pattern. Crucially, 10 of the 12 impulses in the test shot matched impulses in the grassy knoll shot to within 1 millisecond. This is an astounding correlation. Dr. Weiss explained:

* Dr. Barger explained the importance of the WA analysis:

* Actually, due to the fact that the two groups of HSCA acoustical experts worked separately, a math error arose in the calculation of the odds relating to the grassy knoll shot. The probability that the grassy knoll shot was the result of random noise was computed to be less than 5%, or less than 1 in 20, based mainly on a miscalculation of the value of p in the formula. The actual odds are even lower than WA calculated. Dr. Donald Thomas has demonstrated that they are actually only 1 in 100,000, or 100,000 to 1 against (http://jfklancer.com/pdf/Thomas.pdf). Put into percentage terms, the probability that chance produced the grassy knoll shot is 0.001%. To put it another way, the probability that the grassy knoll shot is a gunshot is 99.999%.

Interestingly, in their report, WA pointed out that they had been conservative in calculating the odds that chance had produced the matches between the grassy knoll shot's impulses and the test shot's echo patterns, and that the odds that chance had caused such a high degree of correlation were "considerably less than 5 percent":

* Revealingly, the NRC panel recognized that WA had assigned the wrong value for p in their calculations; however, the panel not only failed to tell their readers that WA had overestimated the odds that the grassy knoll shot was random noise, but they used erroneous assumptions in their own calculations to make it seem like there was a 22% chance that the grassy knoll shot was random noise.

Yes, in so doing, the NRC panel was admitting there was a 78% chance that the grassy knoll shot was a gunshot, but 78% is quite a bit lower than 95%+, and far lower than 99.999%.

There was no grassy knoll shot no matter how many times you attempt to look relevant on this subject. 57 years since the event and no physical evidence for a grassy knoll shot. None. Zero. Zilch. Who exactly is your audience? This is truly bewildering.

[Joe Elliott]

In my previous reply, I explained the timeline and nature of the HSCA acoustical analysis. However, I purposely did not go into much detail on the grassy knoll shot, because that would have made the reply about 50% longer, and it was already long enough. When you understand how Weiss and Aschkenasy (WA) confirmed the grassy knoll shot, you more fully understand the powerful nature of the acoustical evidence.

* The grassy knoll shot is the 145.15 shot, the third of the four shots that the HSCA acknowledged on the dictabelt recording. The BBN scientists noted that this was shot was aimed at JFK when the limousine was “near the limousine position seen in frame 313” (8 HSCA 6).

* The main reason that WA were asked to review the BBN analysis was that BBN said the grassy knoll shot had a certainty factor of only 50%. Everyone recognized that if the 145.15 shot was confirmed to be a shot from the grassy knoll, this would automatically prove that more than one gunman fired at JFK, since no one doubted that at least one shot was fired from behind, and since the sixth-floor gunman could not have fired a shot from the grassy knoll.

BBN said the three other shots had much higher certainty factors:

1st shot: 88% (based on three matches)
2nd shot: 88% (based on three matches)
4th shot: 75% (based on two matches)

* The third shot had a 50% certainty factor because it matched one test-firing shot from the grassy knoll but matched two test-firing shots from the TSBD. The grassy knoll match had a correlation coefficient of 0.8, a very high coefficient, whereas the two TSBD matches had a correlation coefficient of 0.7. Only five other matches of the 15 matches (really correlations) had a coefficient of 0.8. Based on this fact and on other factors, the BBN scientists concluded that the third shot came from the grassy knoll, but they knew that a more-refined analysis was needed to confirm this and to prove that the two TSBD matches were false matches.

The BBN scientists knew that the locations of the microphones in the test-firing caused false alarms/false matches:

They suspected that if they had used more microphones so that the microphones had been closer to each othe3r, the two TSBD matches on the third shot would not have occurred.

* WA realized that the problem was that the microphones in the test firing were spaced 18 feet apart. The 18-foot spacing was the reason that BBN applied a 6-millisecond acceptance window when determining matches.

* As WA explained in their testimony, they did not need to do another test firing in Dealey Plaza to solve the microphone-spacing problem. They knew they could do a computerized sonar analysis that would duplicate the conditions of closer microphone spacing and the resulting echo patterns. They wrote a sonar analysis program that simulated an echo pattern for 180 locations surrounding the location of the test microphone that gave the best match for the third dictabelt impulse pattern, i.e., the grassy knoll shot.

WA had written similar sonar analysis programs for the U.S. Navy—that was one of the reasons the Acoustical Society of America recommended them to the HSCA.

Significantly, the sonar analysis enabled WA to reduce the acceptance window for a match from 6 milliseconds down to 1 millisecond, a 500% narrower window, which vastly reduced the possibility of a false match. WA also applied a noise threshold to further distinguish between non-gunfire noise and gunfire impulses.

* When WA conducted the solar analysis, they found that the dictabelt grassy knoll shot was a practically perfect match for a simulated test-firing shot at a position 5 feet from the microphone position.

In the first sonar analysis comparison, done without the noise threshold, WA found that when the muzzle blast of the test shot was aligned with the first large impulse of the 145.15 shot—the grassy knoll shot—all 26 echoes of the test shot occurred within 1 millisecond of corresponding impulse of the 145.15 shot, an impressive correlation.

In the second sonar analysis comparison, WA found that when they applied the noise threshold, the grassy knoll shot had 14 large impulses compared to the 12 large impulses of the test-shot pattern. Crucially, 10 of the 12 impulses in the test shot matched impulses in the grassy knoll shot to within 1 millisecond. This is an astounding correlation. Dr. Weiss explained:

* Dr. Barger explained the importance of the WA analysis:

* Actually, due to the fact that the two groups of HSCA acoustical experts worked separately, a math error arose in the calculation of the odds relating to the grassy knoll shot. The probability that the grassy knoll shot was the result of random noise was computed to be less than 5%, or less than 1 in 20, based mainly on a miscalculation of the value of p in the formula. The odds are even lower than WA calculated. Dr. Donald Thomas has demonstrated that they are actually only 1 in 100,000, or 100,000 to 1 against (http://jfklancer.com/pdf/Thomas.pdf). To put it another way, there is a 99.999% chance that the grassy knoll shot is a gunshot.

* Revealingly, the NRC panel recognized that WA had assigned the wrong value for p in their calculations; however, the panel not only failed to tell their readers that WA had overestimated the odds that the grassy knoll shot was random noise, but they used erroneous assumptions in their own calculations to make it seem like there was a 22% chance that the grassy knoll shot was random noise.

Yes, in so doing, the NRC panel was admitting there was a 78% chance that the grassy knoll shot was a gunshot, but 78% is quite a bit lower than 95%+ (and far lower than 99.999%).

First of all, it sounds like Weiss and Aschkenasy (W&A) may have compared a lot of locations with 145.15 in the vicinity of the microphone 3 ( 4 ). Perhaps starting 15 feet up the street toward Houston, in a line of 10 feet across. And checked every foot as they went down Elm Street, until they got passed microphone 3 ( 4 ) by 15 feet. So, they might have checked, by computer, a grid of 31 by 11 locations or 341 locations. If there was that many, it might be a mathematical certainty that they would find an excellent correlation, with a hypothetical microphone location. One might not find an excellent correlation with the first of the 341 hypothetical microphone locations, or with the second, but it there might be a high chance one will found before one is done with all 341 hypothetical locations.

I have no idea the size of this array, but for the rest of this post, I will refer to it as the “31 x 11” array, to make it clear what array I am talking about.


Weiss and Aschkenasy (W&A) found a great correlation with the 1963 impulse at 145.15 and one of the Grassy Knoll test shots of 1978.

There were 12 test shots that were compared. 4 of them from the grassy knoll:

Test Shot 5:   Rifle, fired at Target 2 (near z224)
Test Shot 8:  Rifle, fired at Target 3 (near z313)
Test Shot 12:  Rifle, fired at Target 4 (near Mt. Tague)
Test Shot 9: Pistol, fired at Target 3 (near z313)


W&A believe they can predict what the waveform, recorded by 3 ( 4 ) would look like from a certain location five feet away. Did they confirm that?

This can be done with running the calculations for a location where microphone 3 ( 3 ) was. And then comparing the calculated waveform with the real waveform that was recorded at 3 ( 3 ) with the same shot.

Question 1:

Did they confirm that their mathematical model would predict a waveform at 3 ( 1 ), 3 ( 2 ), 3 ( 3 ), 3 ( 5 ), 3 ( 6 ), 3 ( 7 )
by comparing
•   A mathematical calculation of what a Grassy Knoll shot fired at Target 3 would look like at these six locations?
with:
•   The real Grassy Knoll test shot fired at Target 3, recorded at those locations?


If their predictions, based on:
•   The waveform recorded in 1978 for microphone 3 ( 4 )
•   Running the calculations for the locations of 3 ( 1 ), 3 ( 2 ), 3 ( 3 ), 3 ( 5 ), 3 ( 6 ) and 3 ( 7 )
Do not match the recorded 1978 waveforms for what 3 ( 1 ), 3 ( 2 ), 3 ( 3 ), 3 ( 5 ), 3 ( 6 ) and 3 ( 7 ) actually recorded in 1978,
then one cannot put much confidence in the calculations for that spot that was 5 feet from 3 ( 4 ).


Question 2:

Which of these 4 test shots did W&A find the strong correlation with 145.15? Was it 5, 8, 12 or 9?

Question 3:

Did they make as an in-depth search, not just for one of the test shots but of all 4 Grassy Knoll test shots, to find every “Grassy Knoll” correlation they could, over this “31 x 11” array?

Question 4:

Did the make a really in-depth search, of all 12 test shots, to find every correlation they could over this “31 x 11” array?


It is important for to search for correlations, even if they are “impossible”, because they would contradict each other.

If one conducts the same procedure with all 12 test shots:
•   and find no strong correlations, except for Test Shot # 8, at a spot 5 feet from 3 ( 4 ),
that is good.
•   But finds a strong correlation for Test Shot # 8, at a spot 5 feet from 3 ( 4 ),
and finds a strong correlation for Test Shot # 3, at a spot 7 feet from 3 ( 4 ),
and finds a strong correlation for Test Shot # 11, at a spot 2 feet from 3 ( 4 ),
that is bad.

Finding correlations for shots fired from different positions at different targets strongly implies that one is just finding random correlations.



I should note, is that the best thing about the BBN tests, and compiling Exhibit F-367, is that they didn’t limit themselves to only the results that were possible. They could have searched for a correlation near 2 ( 5 ) and as soon as they find one, stop there. But they didn’t, they still searched for other correlations, and found correlations near 2 ( 5 ) for:
•   A shot from the TSBD fired at Target 1 (near z155)
•   A shot from the TSBD fired at Target 3 (near z313)
•   A shot from the Grassy Knoll at Target 4 (Mr. Tague)
If they stopped after finding the first correlation, the data would have looked good. But by being more through, and checking all the other possibilities, they thoroughly test their procedure. Which was found suspect by the multiple and conflicting correlations. But it was good they checked for other “impossible” correlations.

I am concerned that W&A might not have done something similar.

* Actually, due to the fact that the two groups of HSCA acoustical experts worked separately, a math error arose in the calculation of the odds relating to the grassy knoll shot. The probability that the grassy knoll shot was the result of random noise was computed to be less than 5%, or less than 1 in 20, based mainly on a miscalculation of the value of p in the formula. The odds are even lower than WA calculated. Dr. Donald Thomas has demonstrated that they are actually only 1 in 100,000, or 100,000 to 1 against (http://jfklancer.com/pdf/Thomas.pdf). To put it another way, there is a 99.999% chance that the grassy knoll shot is a gunshot.

I must confess that I am a little skeptical that Barger, Weiss and Aschkenasy could have been so far off with their math. Instead of a 1 in 20 chance that the correlations could have been from chance, the odds were actually 1 in 100,000? Math errors of this magnitude are pretty rare for people who are good at math.

Question 5:

Do Dr. Barger, Dr. Weiss and Mr. Aschkenasy all agree with Dr. Thomas on this?


And it does not look good how much these calculations of the odds of these correlations being a result of just chance has changed wildly over the years. It has gone
•   from 1 in 2 (BBN)
•   to 1 in 20 (W&A)
•   to 1 in 25 (Dr. Thomas correcting W&A)
•   to 1 in 100,000 (Dr. Thomas correcting BBN, W&A and himself)

[Michael T. Griffith]

It is interesting to note that when the BBN acoustical scientists began their analysis of the position of the motorcycle with the stuck mike, they did not know that the speed of the motorcycle matched the speed of the motorcade. They only realized the speeds matched after they asked the HSCA for the speed of the motorcade. We learn this from an interview with Dr. Scott Robinson, one of the BBN experts:

We didn’t know what the speed of the motorcade was. And he [Dr. Barger] called somebody at the select committee and asked them to tell him what the speed of the motorcade was. And they looked in their records and told him. And it turned out the speeds matched. And that’s when things got pretty convincing.

Recall, too, that when Weiss and Aschkenasy first heard the dictabelt recording, they doubted that it contained gunfire:

Mr. WEISS. We had no preconception as to what we were going to find. If anything, when we first heard the tape recording and first began to examine the data, our initial reaction was, somebody has got to be kidding; this can't be gunshots. But as we examined the data more carefully, subjected it to all the tests that we have described, the procedures that we have described, the results of the analyses themselves convinced us of where we were heading. Obviously, we did not have any plan or any objective other than to do the best we could to find out what really these data represent.

Mr. ASCHKENASY. If I may--

Mr. FITHIAN . Yes, Sir; go ahead.

Mr. ASCHKENASY. If I may say just one line, it's that the numbers could not be refuted. That was our problem. The numbers just came back again and again the same way, pointing only in one direction, as to what these findings were. There just didn't seem to be any way to make those numbers go away, no matter how hard we tried. (5 HSCA 593)

Finally, I stumbled across a great presentation on the acoustical evidence by Dr. Thomas that he gave in 2003. It is the most in-depth video on the subject that I have seen. It is 52 minutes long.

[Joe Elliott]

Another point I should mention regarding Dr. Thomas’s claim that the 1963 impulse can be matched to a 1978 test shot, to a degree of 1 in 100,000 degree of certainty. These sorts of certainties require ideal conditions.

There was a wind blowing at the time of the assassination that gusted between 10 to 15 mph and the limousine was heading into this head wind. These estimates are based on the effects of the wind on the flags on the limousine and the clothes of the spectators, like Jean Hill and Mary Moorman.

Intuitively, to match a shot made in 1963 with a test shot made in 1978, to such fine precision, that one knew there was “Only a 1 in 100,000” chance the two waveforms were so identical by a fluke of luck, I would think one would need absolutely ideal conditions:
•   Both recordings made by excellent equipment. We know this is not the case of the 1963 recording, recorded by a motorcycle with a stuck transmitter and recorded on the low quality Dictabelt, which was only designed to play back a limited number of times.
•   Both microphones where in the exact same position we known almost certainly did not happen, because the microphones were about 15 feet apart. Indeed W&A calculated the closest microphone was still off of the motorcycle’s position by 5 feet.
•   There was no wind for both recordings, or at least the wind was identical. As far as we know, this was not the case.

It is unbelievable to me, that a 10 to 15 mph wind would not affect the waveforms of a recorded shot enough to make it impossible to match it with a later test shot 15 years later to the probability of 1 in 100,000. To a layman like me, this sounds bogus. Even Weiss and Archkenasy never claimed this level of certainty.

[Joe Elliott]

It is interesting to note that when the BBN acoustical scientists began their analysis of the position of the motorcycle with the stuck mike, they did not know that the speed of the motorcycle matched the speed of the motorcade. They only realized the speeds matched after they asked the HSCA for the speed of the motorcade. We learn this from an interview with Dr. Scott Robinson, one of the BBN experts:

Recall, too, that when Weiss and Aschkenasy first heard the dictabelt recording, they doubted that it contained gunfire:

Finally, I stumbled across a great presentation on the acoustical evidence by Dr. Thomas that he gave in 2003. It is the most in-depth video on the subject that I have seen. It is 52 minutes long.

None of this answer any of my questions from yesterday’s post.

W&A claimed they could calculate what the “shot” would have sounded like from any position near the microphone 3 ( 4 ), and found a good match about 5 five away.

Question 1:

Did they demonstrate that they really could do so? Did they calculate, solely form the 3 ( 4 ) recording, what the waveform would be if recorded at the 3 ( 3 ) position. And found that the calculated waveform matched with the 3 ( 3 ) recording just as well as the calculated waveform (for the position 5 feet from 3 ( 4 ) ) matched the 1963 waveform?

Question 2:

Which of the Test shots did they find match the 1963 waveform? I assume this was Test Shot # 8, the one fired with a rifle (and not a pistol), from the Grassy Knoll, at Target 3. But is this assumption correct?

Question 3:

Did they use the computer to look for correlations not just with Test Shot # 8 but all 12 Test shots?

If their procedure is bound to find strong correlations, because so many potential positions of the microphone are tested for, this will be revealed if strong correlations are also found for other test shots, fired at different targets or from the TSBD.

Question 4:

Do Dr. Barger, Dr. Weiss and Mr. Aschkenasy all agree with Dr. Thomas that they made a huge error in their calculations of the probability that these correlations could be may chance?

Not a 1 in 20 chance but a 1 in 100,000 chance. [/b]