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Acoustics Evidence - Interview with Don Thomas


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I don't want to tell people what to think about the acoustics evidence purportedly recorded on a police dictabelt, as everyone I know already has their mind made up. So I thought instead I would plug the Mary Ferrell Foundation website. We recently recorded a phone interview with Don Thomas, and the audio and transcript of the talk are online, along with about 50 minutes worth of a video presentation he did, plus tons of links to Thomas' essays, essays by his detractors, government reports on the acoustics, and so on. I think it's a good resource page on the acoustics, which is why I'm plugging it here for anyone who is interested. If this spawns a debate on this forum about the acoustics, that's great too.

http://www.maryferrell.org/wiki/index.php/...ted_-_Episode_4

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I don't want to tell people what to think about the acoustics evidence purportedly recorded on a police dictabelt, as everyone I know already has their mind made up. So I thought instead I would plug the Mary Ferrell Foundation website. We recently recorded a phone interview with Don Thomas, and the audio and transcript of the talk are online, along with about 50 minutes worth of a video presentation he did, plus tons of links to Thomas' essays, essays by his detractors, government reports on the acoustics, and so on. I think it's a good resource page on the acoustics, which is why I'm plugging it here for anyone who is interested. If this spawns a debate on this forum about the acoustics, that's great too.

http://www.maryferrell.org/wiki/index.php/...ted_-_Episode_4

Thanks for the Rex.

Do you know if they ever began the work destribed in Jeff Morley's Readers Digest article, and will that process help refine the acoustic study any better?

I didn't get a chance to read it all yet, so sorry if you answer the question elsewhere.

BK

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I don't want to tell people what to think about the acoustics evidence purportedly recorded on a police dictabelt, as everyone I know already has their mind made up. So I thought instead I would plug the Mary Ferrell Foundation website. We recently recorded a phone interview with Don Thomas, and the audio and transcript of the talk are online, along with about 50 minutes worth of a video presentation he did, plus tons of links to Thomas' essays, essays by his detractors, government reports on the acoustics, and so on. I think it's a good resource page on the acoustics, which is why I'm plugging it here for anyone who is interested. If this spawns a debate on this forum about the acoustics, that's great too.

Very useful resource. Any chance of someone providing a summary of where we currently are concerning the acoustic evidence?

http://www.spartacus.schoolnet.co.uk/JFKthomasD.htm

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  • 1 year later...

This is what Jeff Morley has to say about this issue:

http://www.playboy.com/magazine/features/jfk/jfk-page01.html

In the 1970s, some of America's top acoustic scientists studied the recording and the Dallas crime scene and asserted as fact that it contains sound impulses created by the series of gunshots fired at the presidential motorcade. In other words, this acoustic artifact is a kind of soundtrack for Abraham Zapruder's silent home movie. As the film in Zapruder's eight-millimeter camera captured the sight of gunfire hitting the presidential motorcade, this Dictabelt supposedly captured the sounds of the gunshots.

"If it's true that the sound of gunfire is captured on the recording, then it is conclusive evidence," says Paul Hoch, one of the most respected JFK researchers. "There was a conspiracy."

The tape does not contain the sound of gunfire, said five eminent scientists, in the British forensic journal, Science & Justice, in 2005. In 21 pages of closely argued scientific reasoning, physicist Richard Garwin and four colleagues said a careful analysis of the alleged gun shot sounds on Dictabelt #10 shows that they occurred approximately one minute after Kennedy was killed. They were not gunshots at all. Garwin and his colleagues could not say what created the sound impulses heard on Dictabelt #10.

Their article was a response to a 2001 article in Science & Justice which asserted the reverse: that the Dictabelt certainly captured the sounds of gunshots -- and that one of the shots came from the grassy knoll. That article, written by Don Thomas, an insect specialist at the U.S. Department of Agriculture, reviewed the findings of acoustic scientists retained by the House Select Committee on Assassinations in 1978. They concluded that the tape captured sound impulses created by four gunshots, three from the book depository behind Kennedy's limousine and one from the so-called grassy knoll in front of the motorcade. With some important caveats, Thomas says the HSCA got it right.

So who's right? If you don't care to choose your science on the basis of whether it confirms your pre-existing views on Kennedy's murder, you have to consider the two slightly different arguments going on here.

To oversimplify slightly, Garwin and co. focus on the timing of the supposed shots observed on Dictabelt #10, while Thomas focuses on the nature of the sound impulses found on the recording. On these issues, the dueling scientists reach different conclusions that are logical -- and open to legitimate question.

In my subjective view, Garwin and co. have posed a big problem for Thomas but not so big as to exclude a gun shot from the grassy knoll beyond the limits of plausible conjecture.

After all, we already have the photographic evidence from the Zapruder film showing Kennedy hit by a bullet that snapped his head backwards and drove him sideways into the arms of his wife. To say that a bullet fired from the knoll would have pushed Kennedy backward is well within the limits of plausible conjecture, regardless of what you think about the acoustic evidence. If FBI agents Sibert and O'Neill saw a more massive head wound than what's shown in the autopsy photographs, that too might be more evidence of a shot from the front.

"Don has got to confront a basic problem," says Michael O'Dell, one of the leading experts on the JFK acoustics evidence. "How can a 'shot' be fired from the grassy knoll at the same moment that police are responding to the call 'hold everything secure'? It can't."

O'Dell is an unobtrusively brilliant man who lives with his wife in Fresno, California. By day, he runs the technology department of an insurance company. O'Dell is not one of those people drawn to the assassination by interest in the Kennedys or true crime stories or political conspiracies or the Mafia or anything like that -- and that is a great strength of his work. He does not embody the paranoid style in American politics. He embodies the empirical style sorely lacking in most JFK coverage. His methods are detached, analytical, polite and methodical. His e-mail exchanges with Thomas are civil.

He plays the tape of the shots on his desktop computer. You cannot actually hear the shots amidst the drone of engines and snippets of conversation between various Dallas cops. The screen displays the wave forms of the shots that killed Kennedy. Or not. The scratchy sound of the tape, the spiky green lines, made me think of how narrowly scientific methods captured the reality of a president blasted in the head by a bullet and dying in his wife's arms.

O'Dell focuses on the phenomenon known as "cross talk." First, he explains how the Dallas Police Department (DPD) communications system worked. The DPD operated two radio channels. Channel I was for normal police radio traffic and Channel II was assigned for the use of the presidential motorcade. Each channel was recorded by a different device in the DPD radio room. Channel I was recorded on a Dictabelt and Channel II on a Gray Audograph machine. Both machines worked by engraving a track into a plastic medium. The Dictabelt used a rotating cylinder and the Audograph used a flat disk, similar to a phonograph record. The sounds on the two channels are not synchronized because Channel I was recorded constantly while Channel II was voice-activated.

"Crosstalk occurred when sounds from one channel were picked up by a microphone tuned to the other channel," he explained.

An accident of history created the whole controversy. A DPD motorcyclist somewhere in Dallas "had a defective microphone button that caused it to continuously transmit over a five-minute period during which the assassination took place." This accidental transmission began at 12:28 that day, about two minutes before the assassination.

"If this motorcycle had been part of the motorcade," as one dispatcher thought, "it might" -- emphasize might -- "have picked up sounds of the gunshots" and transmitted them to headquarters where they would have been recorded on Channel I. "If true, those sounds could be used to determine how many shots were fired, their timing, and using echo location methods, where the shots came from."

.....Don Thomas is not shaken. He still believes in his 2001 article and its politically loaded conclusion: that Dictabelt #10 captures the sound of a muzzle blast of a gun fired at Kennedy's limousine from the grassy knoll.

"We don't know exactly how the 'hold everything secure' transmission was deposited on the Channel I," he explains. "But we do know there are of lot of skips and jumps caused by the stylus of the dictagraph bouncing out of the groove. You also have to remember the two channels are not synchronized: Channel I is recording constantly from the open microphone on the motorcycle while Channel II is voice activated." This makes determining the timing of all sounds on the recording difficult, if not impossible.

Thomas thinks his critics are straining. "Think about the reality of what they're saying," he says. "They say the grassy knoll shot identified on the recordings is found at the exact moment that Assistant Chief Decker is saying, 'Hold everything secure until we can get homicide investigators up there.' So that must not be the sound of a gunshot. Decker is telling his men, get your ass up on the knoll and see what happened. And these guys are citing that as proof there was no shot from the knoll."

Thomas admits he cannot say exactly how the "hold everything secure" came to be recorded almost simultaneously with the alleged gunshots, but he says Garwin's paper does not change his mind. James Barger, still one the nation's top acoustic scientists, stands by his original findings. "They're talking about corroborative evidence," he says of his critics. "I'm talking about core evidence. I'm trying to explain the five impulses that are on the Dictabelt. We've spent a lot of time debating the timing issues and we'll probably spend a lot more. What they're not talking about is the diabolical coincidence that those impulses matched Barger's recreation both in time and space."

Because the sound matches that Barger found in his Dealey Plaza sound experiment followed a certain pattern, there is an "order of the data" argument that Thomas believes is his trump card. Here's how he puts it in a recent online essay for www.maryferrell.org.

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