Question about Dr. Donald Thomas’s Dictabelt Offset Hypothesis

[Joffrey van de Wiel]

Why no, I don’t mind being called ignorant from someone who has been as evasive as you.


Question for Joffrey van de Wiel

Has Mr. Griffith answered your questions about the number of the “shots” on the Dictabelt recording?
And the timing of these “shots”?
And the source of each “shot” (TSBD, Grassy Knoll, etc.)?
And which Zapruder frame each “shot” corresponds to?

Have you found that there is the excellent correlation between the answers that Mr. Griffith has given you and the Zapruder film as he claims we can find?

Or have you found that Mr. Griffith has been evasive, as I predicted.

And if you haven’t found Mr. Griffith to be evasive, how many “gunshots” are to be found on the Dictabelt recording?


And Joffrey, if you have found Mr. Griffith to be evasive, don’t waste your time and money on Dr. Thomas’s “Hear No Evil”. You will find that Dr. Thomas does not answer these questions either, and is just as evasive as Mr. Griffith.

Sir,

I just noticed your questions for me because my internet connection broke down. I apologize for not responding sooner.

Let me first state then, that I think Mr. Griffith is a very astute researcher and author. I don't think he is being evasive, or is just copying and pasting as a quick way to respond to questions or prove his point. The problem for me is trying to comprehend his (and yours, for that matter) reasoning as I lack sufficient knowledge of physics in general and acoustics in particular. On top of that, I don't understand how a dictabelt recording device works. It is apparently capable of recording human voices, church bells and sirenes, but unable to record the loud bang associated with a gun shot. Then there appear on the recording these high-pitched tones which are unexplained.

I have viewed a presentation of Dr. Thomas on YouTube. Much of it went over my head but as I understand it the following is true:

1) On the day of the assassination, the Dallas Police radio channel 1 was reserved for regular police communications;
2) On the day of the assassination, the Dallas Police radio channel 2 was reserved for the Presidential motorcade;
3) Channel 2 radio traffic was recorded on a Dicta-belt;
4) At a certain time, the microphone of one of the escorting motorcycle officers in the Presidential parade got stuck on the 'transmit' position.

The points of contention are:

1) There was no microphone stuck on the 'transmit' position in the motorcade, and if there was, it was nowhere near Dealey Plaza at 12:30 p.m.;
2) The open microphone did not record any gunshots;
3) The impulses shown on the audiograph are not gunshots but random impulses created by ambient noise;
4) The dictabelt recording can not be matched to the Zapruder film because it has been altered;
5) The four to six shots recorded by the dictabelt contradict the Warren Commission's findings therefore it can not possibly be true;
6) Some gunshot impulses on the recording can not be matched to any test shots, therefore the acoustic evidence is invalid.

I'm missing a few perhaps. I joined this Forum in order to learn something. It is dedicated to a debate about the JFK assassination. A debate is worthless when one is not willing or able to consider the points of view put forward by its participants. I am weighing the evidence put forward by both sides of the equation and hope to come to some sort of conclusion in the near future. 

Meanwhile I remain respectfully yours,

Joffrey

(edited for grammar and translation errors.)

[Michael T. Griffith]

For the sake of those who might be new to the HSCA’s acoustical evidence of four gunshots, or for those who have read one or two articles on the subject and who want to learn more, below are some helpful excerpts from the section on the acoustical evidence in the HSCA’s final report. This report was aimed at the average reader, so the authors made every effort to explain the acoustical evidence in plain English as much as possible. If you are trying to make heads or tails of this thread, these excerpts should be helpful.

To the human ear, the tapes and Dictabelts contain no discernible sounds of gunfire. The dispatcher's voice notations of the time of day indicate that channel 2 apparently was not in use during the period when the shots were fired. Channel 1 transmissions, however, were inadvertently being recorded from a motorcycle or other police vehicle whose radio transmission switch was stuck in the "on" position.(10) BBN was asked to examine the channel 1 Dictabelts and the tape that was made of them to see if it could determine: (1) if they were, in fact, recorded transmissions from a motorcycle with a microphone stuck in the "on" position in Dealey Plaza; (2) if the sounds of shots had been, in fact, recorded; (3) the number of shots; (4) the time interval between the shots; (5) the location of the weapon or weapons used to fire the shots; and (6) the type of weapon or weapons used.

BBN converted the sounds on the tape into digitized waveforms and produced a visual representation of the waveforms.(11) By employing sophisticated electronic filters, BBN filtered out "repetitive noise," such as repeated firings of the pistons of the motorcycle engine.(12) It then examined the tape for "sequences of impulses" that might be significant. (A "sequence of impulses" might be caused by a loud noise--such as gunfire--followed by the echoes from that loud noise.) Six sequences of impulses that could have been caused by a noise such as gunfire were initially identified as having been transmitted over channel 1.(13) Thus, they warranted further analysis.

These six sequences of impulses, or impulse patterns, were subjected to preliminary screening tests to determine if any could be conclusively determined not to have been caused by gunfire during the assassination. The screening tests were designed to answer the following questions:(14)

-- Do the impulse patterns, in fact, occur during the period of the assassination?
-- Are the impulse patterns unique to the period of the assassination?
-- Does the span of time of the impulse patterns approximate the duration of the assassination as indicated by a preliminary analysis of the Zapruder film? (Are there at least 5.6 seconds between the first and last impulse? 4)
-- Does the shape of the impulse patterns resemble the shape of impulse patterns produced when the sound of gunfire is recorded through a radio transmission system comparable to the one used the Dallas police dispatch network?
-- Are the amplitudes of the impulse patterns similar to those produced when the sound of gunfire is recorded through a transmission system comparable to the one used for the Dallas police dispatch network?

All six impulse patterns passed the preliminary screening tests.(15)

BBN next recommended that the committee conduct an acoustical reconstruction of the assassination in Dealey Plaza to determine if any of the six impulse patterns on the dispatch tape were caused by shots and, if so, if the shots were fired from the Texas School Book Depository or the grassy knoll.(16) The reconstruction would entail firing from two locations in Dealey Plaza--the depository and the knoll--at particular target locations and recording the sounds through numerous microphones. The purpose was to determine if the sequences of impulses recorded during the reconstruction would match any of those on the dispatch tape. If so, it would be possible to determine if the impulse patterns on the dispatch tape were caused by shots fired during the assassination from shooter locations in the depository and on the knoll.(17). . . .

. . . it was deemed judicious to seek an independent review of Barger's analysis before proceeding with the acoustical reconstruction. So, in July 1978, the committee contacted the Acoustical Society of America to solicit recommendations for persons qualified to review the BBN analysis and the proposed Dallas reconstruction. The society recommended a number of individuals, and the committee selected Prof. Mark Weiss of Queens College of the City University of New York and his research associate, Ernest Aschkenasy. Professor Weiss had worked on numerous acoustical projects. He had served, for example, on the panel of technical experts appointed by Judge John J. Sirica to examine the White House tape recordings in conjunction with the Watergate grand jury investigation. Aschkenasy had specialized in developing computer programs for analyzing large volumes of acoustical data. . . .

A recording was made of the sounds received at each microphone location during each test shot, making a total of 432 recordings of impulse sequences (36 microphone locations times 12 shots), or "acoustical fingerprints," for various target-shooter-microphone combinations. Each recorded acoustical fingerprint was then compared with each of the six impulse patterns on the channel 1 dispatch tape to see if and how well the significant points in each impulse pattern matched up. The process required a total of 2,592 comparisons (432 recordings of impulse sequences times six impulse patterns), an extensive effort that was not completed until 4 days before Barger was to testify at a committee public hearing on September 11, 1978.(26)

The time of the arrival of the impulses, or echoes, in each sequence of impulses was the characteristic being compared, not the shape, amplitude or any other characteristic of the impulses or sequence.(27) If a point (representing time of arrival of an echo) in a sequence of the 1963 dispatch tape could be correlated within plus or minus 6/1,000 of a second to a point in a sequence of the reconstruction, it was considered a match.(28)

A plus or minus 6/1,000 of a second "window" was chosen, because the exact location of the motorcycle was not known. Since the microphones were placed 18 feet apart in the 1978 reconstruction, no microphone was expected to be in the exact location of the motorcycle microphone during the assassination in 1963. Since the location was not apt to be exactly the same, and the time of arrival of the echo is unique at each spot, the +-6/1,000 of a second "window" would allow for the contingency that the motorcycle was near, but not exactly at, one of the microphone locations selected for the reconstruction.(29)

Those sequences of impulses that had a sufficiently high number of points that matched (a "score" or correlation coefficient of .6 or higher) were considered significant.(30) The "score" or correlation coefficient was set at this level to insure finding all sequences that might represent a true indication that the 1963 dispatch tape contained gunfire. Setting it at this level, however, also allowed a sequence of impulses on the dispatch tape that might have been caused by random noise or other factors to be considered a match and therefore significant.(31) Such a match, since it did not in fact represent a true indication of gunfire on the 1963 dispatch tape, would be considered an "invalid match."(32)

Of the 2,592 comparisons between the six sequences of impulses on the 1963 police dispatch tape and the sequences obtained during the acoustical reconstruction in August 1978, 15 had a sufficient number of matching points (a correlation coefficient of .6 or higher) to be considered significant.(33) The first and sixth sequence of impulses on the dispatch tape had no matches with a correlation coefficient over .5. The second sequence of impulses on the dispatch tape had four significant matches, the third sequence had five, the fourth sequence had three, and the fifth sequence had three.(34) Accordingly, impulses one and six on the dispatch tape did not pass the most rigorous acoustical test and were deemed not to have been caused by gunfire from the Texas School Book Depository or grassy knoll.(35) Additional analysis of the remaining four impulse sequences was still necessary before any of them could be considered as probably representing gunfire from the Texas School Book Depository or the grassy knoll.

The locations of the microphones that recorded the matches in the 1978 reconstruction were plotted on a graph that depicted time and distance. It was observed that the location of the microphones at which matches were recorded tended to cluster around a line on the graph that was, in fact, consistent with the approximate speed of the motorcade (11 mph), as estimated from the Zapruder film.(36) For example, of the 36 microphones placed along the motorcade route, the one that recorded the sequence of impulses that matched the third impulse on the 1963 dispatch tape was farther along the route than the one that recorded the impulses that matched the second impulse on the dispatch tape. The location of the microphones was such, it was further observed, that a motorcycle traveling at approximately 11 miles per hour would cover the distance between two microphones in the elapsed time between impulses on the dispatch tape. This relationship between the location of the microphones and the time between impulses was consistent for the four impulses on the dispatch tape, a very strong indication, the committee found, that the impulses on the 1963 dispatch tape were picked up by a transmitter on a motorcycle or other vehicle as it proceeded along the motorcade route. Applying a statistical formula, Barger estimated that since the microphones clustered around a line representing the speed of the motorcade, there was a 99 percent probability that the Dallas police dispatch tape did, in fact, contain impulses transmitted by a microphone in the motorcade in Dealey Plaza during the assassination.(37). . . .

In mid-September 1978, the committee asked Weiss and Aschkenasy, the acoustical analysts who had reviewed Barger's work, if they could go beyond what Barger had done to determine with greater certainty if there had been a shot from the grassy knoll. Weiss and Aschkenasy conceived an analytical extension of Barger's work that might enable them to refine the probability estimate.(45) They studied Dealey Plaza to determine which structures were most got to have caused the echoes received by the microphone in the 1978 acoustical reconstruction that had recorded the match to the shot from the grassy knoll. They verified and refined their identifications of echo-generating structures by examining the results of the reconstruction. And like BBN, since they were analyzing the arrival time of echoes, they made allowances for the temperature differential, because air temperature affects the speed of sound.(46) Barger then reviewed and verified the identification of echo-generating sources by Weiss and Aschkenasy.(47)

Once they had identified the echo-generating sources for a shot from the vicinity of the grassy knoll and a microphone located near the point indicated by Barger's tests, it was possible for Weiss and Aschkenasy to predict precisely what impulse sequences (sound fingerprints) would have been created by various specific shooter and microphone locations in 1963.(48) (The major structures in Dealey Plaza in 1978 were located as they had been in 1963.) Weiss and Aschkenasy determined the time of sound travel for a series of sound triangles whose three points were shooter location, microphone location and echo-generating structure location. While the location of the structures would remain constant, the different combinations of shooter and microphone locations would each produce a unique sound travel pattern, or sound fingerprint.(49) Using this procedure, Weiss and Aschkenasy could compare acoustical fingerprints for numerous precise points in the grassy knoll area with the segment identified by Barger on the dispatch tape as possibly reflecting a shot fired from the knoll.(50) 10

Because Weiss and Aschkenasy could analytically construct what the impulse sequences would be at numerous specific shooter and microphone locations, they decided to look for a match to the 1963 police dispatch tape that correlated to within ±1/1.000 of a second, as opposed to +-6/1.000) of a second, as Barger had done.(51) By looking for a match with such precision, they considerably reduced the possibility that any match they found could have been caused by random or other noise,(52) thus substantially reducing the percentage probability of an invalid match. . . .

Approximately 10 feet from the point on the grassy knoll that was picked as the shooter location in the 1978 reconstruction and four feet from a microphone location which, Barger found, recorded a shot that matched the dispatch tape within +-6/1,000 of a second, Weiss and Aschkenasy found a combination of shooter and microphone locations they needed to solve the problem. It represented the initial position of a microphone that would have received a series of impulses matching those on the dispatch tape to within +-1/1.000 of a second. The microphone would have been mounted on a vehicle that was moving along the motorcade route at 11 miles per hour.

Weiss and Aschkenasy also considered the distortion that a windshield might cause to the sound impulses received by a motorcycle microphone. They reasoned that the noise from the initial muzzle blast of a shot would be somewhat muted on the tape if it traveled through the windshield to the microphone. Test firings conducted under the auspices of the New York City Police Department confirmed this hypothesis. Further, an examination of the dispatch tape reflected similar distortions on shots one, two, and three, when the indicated positions of the motorcycle would have placed the windshield between the shooter and the microphone.11 On shot four, Weiss and Aschkenasy found no such distortion.(55) The analysts' ability to predict the effect of the windshield on the impulses found on the dispatch tape, and having their predictions confirmed by the tape, indicated further that the microphone was mounted on a motorcycle in Dealey Plaza and that it had transmitted the sounds of the shots fired during the assassination.

Since Weiss and Aschkenasy were able to obtain a match to within +-1/1,000 of a second, the probability that such a match could occur by random chance was slight. Specifically, they mathematically computed that, with a certainty factor of 95 percent or better, there was a shot fired at the Presidential limousine from the grassy knoll.(56)

Barger independently reviewed the analysis performed by Weiss and Aschkenasy and concluded that their analytical procedures were correct.(57) Barger and the staff at BBN also confirmed that there was a 95 percent chance that at the time of the assassination a noise as loud as a rifle shot was produced at the grassy knoll. When questioned about what could cause such a noise if it were not a shot, Barger noted it had to be something capable of causing a very loud noise--greater than a single firecracker.(58) Further, given the echo patterns obtained, the noise had to have originated at the very spot behind the picket fence on the grassy knoll that had been identified,(59) indicating that it could not have been a backfire from a motorcycle in the motorcade.(60)

In addition, Barger emphasized, the first part of the sequence of impulses identified as a shot from the grassy knoll was marked by an N-wave, a characteristic impulse caused by a supersonic bullet.(61) The N-wave, also referred to as a supersonic shock wave, travels faster than the noise of the muzzle blast of a gun and therefore arrives at a listening device such as a microphone ahead of the noise of a muzzle blast. The presence of the N-wave was, therefore, a significant additional indication that the third impulse on the police dispatch tape represented gunfire, and, in particular, a supersonic bullet.(62) The weapon may well have been a rifle, since most pistols except for some such as a .44 magnum--fire subsonic bullets. The N-wave was further substantiation for a finding that the third impulse represented a shot fired in the direction of the President. Had the gun been discharged when aimed straight up or down, or away from the motorcade, no N-wave would have appeared.(63) Of the impulse patterns on the dispatch tape that indicated shots from the book depository, those that would be expected to contain an N-wave, given the location of the vehicle's microphone, did so, further corroborating the conclusion that these impulses did represent supersonic bullets.(64) (HSCA report, pp. 68-75)

[Gerry Down]

2) The open microphone did not record any gunshots;
3) The impulses shown on the audiograph are not gunshots but random impulses created by ambient noise;

This is what gets me. Shouldn't a person be able to hear shots on the dictabelt recording?

[Michael T. Griffith]

The points of contention are:

1) There was no microphone stuck on the 'transmit' position in the motorcade, and if there was, it was nowhere near Dealey Plaza at 12:30 p.m.;
2) The open microphone did not record any gunshots;
3) The impulses shown on the audiograph are not gunshots but random impulses created by ambient noise;
4) The dictabelt recording can not be matched to the Zapruder film because it has been altered;
5) The four to six shots recorded by the dictabelt contradict the Warren Commission's findings therefore it can not possibly be true;
6) Some gunshot impulses on the recording can not be matched to any test shots, therefore the acoustic evidence is invalid.

Let me answer these by their number.

1. We know this is wrong because the Channel 2 dispatcher told all the patrolmen that a patrolman "up on Stemmons" had his mike stuck on, and he asked them to try to find him and get him to shut off his mike. The "up on Stemmons" comment is evidence that McClain was the one with the stuck mike.

2. This is a summary claim that I think is totally refuted by the evidence. For example, there are N-waves from supersonic rifle fire on the dictabelt on the shots that were recorded when the microphone was in a position to record N-waves, and the grassy knoll shot's N-wave comes 24 milliseconds before its trailing muzzle blast, just as it should. N-waves from rifle fire typically come 10-30 milliseconds before the muzzle blast behind them. 

3. This is another summary claim that I think is also totally refuted by the evidence. The correlations between the dictabelt gunfire impulse patterns and the test-firing impulse patterns are powerful, compelling evidence that the dictabelt contains recorded assassination gunfire.

4. Yet, there are definite correlations between the dictabelt gunshots and gunfire reactions in the Zapruder film, somewhat to my surprise. It is entirely possible that the Zapruder film was not altered enough to prevent it from correlating with the dictabelt. Much of the alteration involved adding, removing, and doctoring images on the film, which would not affect correlation with the dictabelt. Also, since the dictabelt might not have recorded one of the shots fired at JFK, because of how the shot was fired and because of the DPD dispatch system's AGC circuitry, it just might be that this unrecorded shot is part of the reason that the dictabelt does correlate rather well with the Zapruder film.

5. Yes, believe it or not, some people make that argument.

Speaking of the WC, we now know that the commission had an analysis done on a KBOX radio station recording that was made in Dealey Plaza during the assassination. The analysis was done by acoustical expert Larry Kersta at the Bell Telephone Lab in New Jersey. Kersta only had the equipment to do a spectrographic analysis of the tape, but he found that it contained six "non-voiced" noises! Moreover, the KBOX "non-voiced" noises follow the same sequence and pattern as do the six dictabelt impulses that passed the first BBN screening for gunfire: the first one is different from the others, followed by three impulses close together, followed by a slight pause, followed by two more impulses similar to the previous three. My, my, my, what an amazing coincidence.

6. I don't know who said that, but they must not have read any of the HSCA materials. Only five of the impulse patterns met all of the BBN screening criteria for gunfire, and all five of those impulse patterns match shots from the Dealey Plaza test firing. I might add that no other impulse pattern anywhere on the 5.5-minute dictabelt segment met all the BBN criteria for gunfire.

[John Iacoletti]

Speaking of the WC, we now know that the commission had an analysis done on a KBOX radio station recording that was made in Dealey Plaza during the assassination.

Which, by the way, is one of the many original pieces of evidence that "can't be located".  The common recording we've all heard ("it appears something has happened in the motorcade route") is a re-creation.

[Joe Elliott]

Joe, it would be easier to follow your argument by using the actual material published by Dr. Thomas and object to what you believe is wrong. One source of "Hear No Evil" is here: http://www.whokilledjfk.net/hear_no_evil.htm

If you go to section FILMED EVIDENCE OF THE MOTORCYCLE you have a table of shots and Z-frames (Table 1). It says that "Tape Times from BBN Report Table 2.", which I haven't checked, but the times you're asking for should be there.

Edit: unfortunately the figures don't display in the url I listed above.

Thank you Otto. This information is most helpful. I’ll start another thread on it in a day or two. At a glance, I can see why Mr. Griffith was not giving us this information directly, even though, the initial impression, is that it matches up with the Zapruder film. But I will show that this is bogus.

What a bunch of lying nonsense. I have provided links to Dr. Thomas's articles in several of my replies. I've also provided citations from his book in some of my replies. I've also provided a link to one of Dr. Thomas's videos on the acoustical evidence. Just a few replies ago, I provided a link to one of Dr. Thomas's discussions on correlating the dictabelt and the Zapruder film. I also cited the pages in his book where he discusses this issue.

No. You provided a bunch of links without saying which link has the information I requested. Otto, in contrast, gave me just one link, that was just a few pages long, that provided the information.

You provided no link to (until after Otto did):

http://www.whokilledjfk.net/hear_no_evil.htm

Or any other similar website where the information is right there.


You don’t have to find such a website. It would have been as simple just type out:

The BBN found shots at z175 (TSBD), z204 (TSBD), z312 (Knoll) and z326 (TSBD). And Dr. Thomas found a fifth at z224 (TSBD).


I think that you wanted to keep it a secret, at least from the casual views, of a first shot at z175, which really make it difficult for Officer McLain to be there for the first shot.

[Joe Elliott]

The points of contention are:

Actually, I’m am certain we have only seen a portion of the tip of the iceberg so far.

1) There was no microphone stuck on the 'transmit' position in the motorcade, and if there was, it was nowhere near Dealey Plaza at 12:30 p.m.;

1. We know this is wrong because the Channel 2 dispatcher told all the patrolmen that a patrolman "up on Stemmons" had his mike stuck on, and he asked them to try to find him and get him to shut off his mike. The "up on Stemmons" comment is evidence that McClain was the one with the stuck mike.

Joffrey. There was a motorcycle with a stuck ‘transmit’ button, but it was not with the motorcade. It was at the Trade Mart.

I see you watched the 40-minute video by Dr. Thomas. In it, he seems to make an overwhelming case that the motorcycle with the stuck microphone was with the motorcade, because he played an 8-second clip of the sounds of loud sirens, exactly the sort of thing that would be recorded by a motorcycle going with the President to the hospital.

However, if one does not “cherry pick”, as Dr. Thomas did, which section of the tape to play, but played the whole thing for the 5 minute trip to the hospital, you would have heard:

Very little
Sirens approaching from the distance, then getting louder, then quite loud for a few seconds, then get less loud and receding the distance.
And again, the same patter with the sirens, getting loud and receding.
And again, the same patter with the sirens for the third time, getting loud and receding.

This is not consistent with a motorcycle travelling with its sirens on to the hospital for the full 5 minutes. This is consistent with a motorcycle waiting at the Trade Mart Center for the President, and hearing the sirens as they passed right by on the freeway. The Trade Mart center was very close to where the limousine was as it rushed to the hospital.

I claim, it was dishonest for Dr. Thomas to play just a short clip. I am very confident that Mr. Griffith will not make available to you a recording of this entire 5-minute span, no more than Dr. Thomas did.

2) The open microphone did not record any gunshots;

Since the motorcycle appears not to have been with the motorcade, it could not have recorded the gunshots.

But one thing that is beyond dispute, is that many of these “sound impulses” were not gunshots.

Below is a quote from Dr. Barger with the BBN, who gave testimony to the HSCA in 1978 in support of the acoustic data.

Dr. BARGER - Yes. We examined the full 234 linear feet of the waveform representing the output of the channel 1 recording when the button was stuck to see if there were any other impulsive patterns that occurred that were similar to these that we are looking at on channel 1. We found that there was one other sequence of impulsive events. It was dissimilar from the one we have looked at principally in that its timespan was less than 5 seconds. It occurred about a minute later than the period of impulses in question. We found no other impulsive patterns on the tape.

So, about a minute after the alleged gunshots, there was another of multiple sound impulses. No one is saying there was several seconds of gunshots, followed by a minute of quiet, followed by another flurry of gunshots.

Also, of the 7 sound impulses that were recorded at the time of the alleged gunshots, 4 sound impulses were accepted as gunshots, 3 were rejected by the BBN. Years later, Dr. Thomas said one of these was a real gunshot. And it just happens to corresponds to z224 so I suspect Dr. Thomas wanted at least two of the gunshots at z224 and z313, to match the Zapruder film better.

Now, who knows, I don’t know the absolute truth. But one thing I can say for certain. Most of the sound impulses on that tape were not caused by gunshots. And likely none of them were.

3) The impulses shown on the audiograph are not gunshots but random impulses created by ambient noise;

I don’t know the technical reason. I heard the vibration of the engine could caused these sound impulses, these “N-waves”. I don’t think anyone knows for certain. But there are too many of them and too much spread over time for them to all have been gunshots.

4) The dictabelt recording can not be matched to the Zapruder film because it has been altered;

Actually, if one accepts that Dr. Thomas shot at ‘140.32 seconds”, that matches up well with the BBN shot at ‘145.15 seconds” A gap of 4.83 seconds which is within a tenth of a second of the gap between z224 and z312, when many people, including me, say two shots did occur. Well, that’s pretty amazing, isn’t it. I mean the odds of that are something like one in a hundred of that happening, correct?

No. Remember there were 7 sound impulses within a few seconds of each other. Mathematics says that there are 7*6/2 or 21 possible unique pairs. “Shots 1 and 2”, “Shots 1 and 3”, etc. So, the real odds are not 1 in 100 but more like 1 in 5.

And maybe somewhat less, because there was another cluster of “shots” a minute afterwards that the BBN could have focused on. They made have focused on the one they chose because they knew about this 4.83 second gap between two of the sound impulses in the first cluster.

This is similar to the problem where a teacher, year after year, finds that often, two of his students in his class have the same birthday. With 22 students, there are 22*21/2 or 231 unique pairs. More than half of 365. So, it is not a vast coincidence for him to discover such pairing in many years.

5) The four to six shots recorded by the dictabelt contradict the Warren Commission's findings therefore it can not possibly be true;

Yes, it would.

5. Yes, believe it or not, some people make that argument.

Speaking of the WC, we now know that the commission had an analysis done on a KBOX radio station recording that was made in Dealey Plaza during the assassination. The analysis was done by acoustical expert Larry Kersta at the Bell Telephone Lab in New Jersey. Kersta only had the equipment to do a spectrographic analysis of the tape, but he found that it contained six "non-voiced" noises! Moreover, the KBOX "non-voiced" noises follow the same sequence and pattern as do the six dictabelt impulses that passed the first BBN screening for gunfire: the first one is different from the others, followed by three impulses close together, followed by a slight pause, followed by two more impulses similar to the previous three. My, my, my, what an amazing coincidence.

Joffrey, the KBOX recording was a recreation. They did NOT record the assassination as it happened.

It was similar to the 1938 Orson Wells broadcast of the “War of the Worlds”, where they didn’t record a real invasion of the Earth from Mars, but a fake one.

At the end of the day, I admit, it is conceivable that the Dictabelt did have a recording of the assassination, despite all the evidence against it. But there is no way this KBOX recreation from a latter day recorded the gunshots at Dealey Plaza.

6) Some gunshot impulses on the recording can not be matched to any test shots, therefore the acoustic evidence is invalid.

No. If most did not match at all, but a few matched very very well, that would be of much interest. Now before we go on, I should say that I am very good at mathematics. At algebra, calculus, trigonometry, at least when I have been practicing. But not so good at statistics. So, take what I say with a grain of salt.

Correlations between two data sets can be measured, like between the data from 1963 and the data from a 1978 test, to get something called a “Correlation Coefficient”. This coefficient must always be between -1 and +1. If outside that range, an error in calculation has occurred. A correlation of +1 is very good. A perfect match of data. A correlation of -1 is very bad, because you always get the opposite results. Actually, this might be good because if a bad model predicted one result, you would know the opposite would always actually happen. And a correlation of 0, means the comparisons are random. Occasionally a match is found, but this is just by luck.

https://en.wikipedia.org/wiki/Pearson_correlation_coefficient

A correlation of 0.8 may be very low if one is verifying a physical law using high-quality instruments, but may be regarded as very high in the social sciences, where there may be a greater contribution from complicating factors.

The BBN tested, believe it or not, over 2,600 hundred tests. 78 gunshots, recorded at 36 microphones. I make it out to be 2,808 tests. Of these 15 had a correlation coefficient of 0.6 or greater. And 4 were found with a correlation coefficient of 0.8, which caused the BBN to conclude that these were shots. I should think one should find some correlations with 2,808 possibilities.

Now, to a layman like me, this seems questionable, since 0.8 provides a low degree of confidence. Although it could be asked “Is the Dictabelt recording a “high-quality” instrument?” I would guess not.

Still checking 2,808 results and finding 4 somewhat weak correlations, of only 0.8, does not sound impressive to me. But when it comes to statistics, I am well out of my depth.

[Michael T. Griffith]

Now that’s what I call experts.

What kind of an expert would make calculations that are off by more than 3 orders of magnitude? They calculated the odds as 1 and 20, but with the correct calculations the odds are 1 in 100,000. I don’t believe in Dr. Thomas’s one in 100,000 odds any more than I believe in the 1978 HSCA acoustic experts 1 in 20 odds.

Oh! Okay! So I take it you say the same thing about the numerous egregious errors in the NRC panel's report, right? Right? Right? Yeah, uh-huh. No, you won't, because you don't deal with the evidence honestly or objectively.

The HSCA experts used the wrong value for one of the values that went into their calculations of the odds. The calculations themselves were done correctly, but they were off because of the errant value that was used. And, as mentioned, if they had used not used the incorrect value, they would have discovered that the odds that the correlations were coincidence were far more remote than they calculated. With the errant value, they calculated the odds of the correlations being coincidence as less than 1 in 20, or less than 5%, when in actuality the odds are 1 in 100,000.

Not when the positions of the motorcycles make the odds zero.

More of your amateurish jibberish. Are you ever, ever, ever going to deal with Dr. Thomas's section on the position of McClain's motorcycle in his book Hear No Evil?