Early study of Acoustics Evidence?

[Matt Allison]

Is the original evidence that BB&N used available anywhere? The tools we use in sound analysis today are light years ahead of what was used in 1978, and it would be really informative to see their actual data; the graphs, charts, etc.

[Joseph McBride]

Is this the mock trial he talks about? https://www.imdb.com/title/tt0983902/fullcredits?ref_=tt_cl_sm#cast

[Matt Allison]

Like most of us, I've got some free time so I'll load that Dictabelt file into Pro Tools. This will be my starting guide:

http://www.montana.edu/rmaher/publications/maher_ieeesafe_0407_109-113.pdf

I'll post some pics and details of whatever I come up with later tonight.

[Matt Allison]

On 4/9/2020 at 7:59 PM, Chris Bristow said:

 

Dictabelt.m4a 1.95 MB · 2 downloads motoridle copy.wav 43.13 kB · 0 downloads

Hi Chris- the file labeled "Dictabelt" sounds like a copy made by someone holding a recorder or microphone up to a speaker and then recording it. Is that the case? Does anyone have a link to a copy of the dictabelt that is closer to the original?

[James DiEugenio]

Joe:

That might be it, but that trial was in England and the production company that did it was in England.

 

[Matt Allison]

It looks like there is BBN data at Mary Ferrell, which is helpful. There is a paper by Michael O'Dell that discusses his attempt to sync the Ch 1 recording and the Ch 2 recording using Decker's "Hold everything" message while using 60 cycle hum to maintain the tape's correct speed; seems well done to me, I'd be curious if Don Thomas had a rebuttal to it or what his thoughts are.

[Chris Bristow]

17 hours ago, James DiEugenio said:

 Chris, then you think the sounds are not gunshots then?

What could they be?

I am not saying I am an acoustics believer, but this is the problem you have here.  

James, I suppose if Mclain is correct they can't be gunshots. But I don't have the knowledge to consider if there are other valid explanations. Joseph's comment about Gary Mack is very interesting and that would explain everything but it is the first I have heard of that so I can't say anything. Yes it is a problem and if there is no other reason for those spikes I would have to consider Mclain may be wrong. But Gary Mack may have been involved with a forgery to discredit the HSCA and if so I doubt he left a smoking gun. That would make the issue a bottomless rabbit hole.
I know they Harley 45 sound is totally subjective but the rpm and whistling is very convincing. I don't think you could ever have a mic in that location and not have the engine sound as the main component of the recording.

[Chris Bristow]

2 hours ago, Matt Allison said:

Hi Chris- the file labeled "Dictabelt" sounds like a copy made by someone holding a recorder or microphone up to a speaker and then recording it. Is that the case? Does anyone have a link to a copy of the dictabelt that is closer to the original?

I thought I downloaded the file but can't be sure of my memory. My old hard drive is long dead.

[Cliff Varnell]

What a crock!

Does the acoustics evidence prove anything we don’t know from the physical evidence found with the body, the properly prepared autopsy material, and the contemporaneous reports of witnesses in position of authority?

Why muddle the prima facie case for conspiracy with highly technical redundancies?

[James DiEugenio]

I should add that Thompson is a disciple of the acoustics evidence, swears by it. 

For his upcoming book, which I think is called One Second in Dallas, he is going to make it a keystone of his presentation.

From what I heard, he was in contact with those two guys from the HSCA who did the final testing on this.

Since Thompson has a name, and his first book on the case was on the cover of the Saturday Evening Post, his book should get some buzz.

Edited April 12, 2020 by James DiEugenio

[James DiEugenio]

Thomas deals with O'Dell in his book on pages 638-41.

He says the test results of the "regression analysis does not prove that there are impositions on CH 1 only that such explanation is consistent with the data, a better fit that the assumption made by the NRC panel that all impositions are on CH 2."

He then concludes that the attempt to synchronize by the cross talk is not tenable due to the time offsets.

 

He later says that O'Dell tried to postulate that GK gunshot was caused by radio noise or someone's voice.(p. 643)

Like I said, I am not an acoustics disciple,  but could two professional groups, who were among the finest acoustics analysts there were, really be that wrong?  From my understanding, BBN and W and A were the two best in the business.

Edited April 12, 2020 by James DiEugenio

[Chris Bristow]

17 hours ago, Eddy Bainbridge said:

It is important to be aware of the strength of the acoustic evidence: The analysis proposes that the wave form created by test shots fired from the TSBD matches with a high degree of probability the sounds on the Dictabelt. The sounds are timed on the tape to accurately match the assassination timing. The sequence of the shots matches the hypothetical positions of a microphone travelling at the speed of the motorcade. 

If the acoustic evidence is to be rejected, then there are some astonishing coincidences to be faced. 

I am not an acoustic expert but the dictabelt is a filtered recording of the actual sounds. To suggest you can listen to the recording and state what type of engine can be heard needs to  consider what effect the filtering had. 

To accept the testimony of McClain as accurate, one needs to consider what influences may have come to bear on his testimony. 

Yes the 45ci sound is very subjective. what is also subjective but much more compelling to me is the whistle. Whether a person is a whistler or not is usually something they know innately. I can't see anyone not recognizing the sound of their own whistle and others not being able to quickly identify someone they know from their whistle.
What is not as subjective is that 2200rpm sound that only happens when we hear the keyed mic. even if the dicta belt frequency is filtered to record within the range of the human voice or the mic is designed that way or is omni directional(I think you need a longer mic like a handheld announcers mic for that) background sounds seem to be heard. I cannot imagine a mic not picking up the engine sound as the main background sound. If it is not an engine then something else was repeating at 2200 cpm and only when that mic was transmitting. What could explain that?
I do have some questions about the timing of the shots since 313 is the only one we can be sure of. I have heard anywhere from 209 to 223 for the throat shot. So I have some reading to do.
As to the sound matching the speed of the motorcade Mclain said he was at a stop when he saw the head shot. He was matching the motorcade and it was bunching up to make the turn on Elm as he came to a stop. So as he pulled to a stop he must have been crawling along in the 5 seconds before the head shot, then he was fully stopped at the head shot. Still I guess in slowing from about 5mph to zero he traveled 25 feet maybe.
      As I recall they set up microphones around the plaza to record the test shots. If they had placed Mclain's bike at the location he stopped at and opened the mic to record the test shots to the actual dicta belt it would have been so valuable. Would also like to hear other dicta belt recording from the Dallas PD.
So I can't explain the engine sound or those big peaks that conform to gunshots. If Joseph's post about Gary Mack is correct then all bets are off. If it is possible and has compelling circumstantial evidence it throws a monkey wrench into the entire issue.
  It does seem that explaining the 2200rpm happening only when the mic was keyed is just as difficult as explaining gunshot sound that are not gunshots. I'm am stuck either way!
You know who could of solved this whole thing is the dispatcher who worked with the officers in question. They would have heard each officers engine so may times I bet they could identify people just by the engine sound. And I don't mean 45 vs 1200 I mean. I spent 5 years on radios and hung out in dispatch. you could often tell each individual by very subtle aspects of the transmission.

 

[Chris Bristow]

23 hours ago, Joseph McBride said:

I write about this audiotape in INTO THE NIGHTMARE.  Mary Ferrell was an intelligence asset who planted the dubious

tape to discredit the HSCA, using it "like a planted mine sure to go off and destroy everything that surrounded it." Gary Mack was also involved in this operation.

Very interesting. Going to look for the book. EDIT: Found your podcast.

Edited April 12, 2020 by Chris Bristow

[Matt Allison]

2 hours ago, James DiEugenio said:

Thomas deals with O'Dell in his book on pages 638-41.

He says the test results of the "regression analysis does not prove that there are impositions on CH 1 only that such explanation is consistent with the data, a better fit that the assumption made by the NRC panel that all impositions are on CH 2."

He then concludes that the attempt to synchronize by the cross talk is not tenable due to the time offsets.

Thanks Jim. I need to read up some more on this subject so I can get a firm grip on what it is all about.

[Matt Allison]

3 hours ago, Chris Bristow said:

What is not as subjective is that 2200rpm sound that only happens when we hear the keyed mic. even if the dicta belt frequency is filtered to record within the range of the human voice or the mic is designed that way or is omni directional(I think you need a longer mic like a handheld announcers mic for that) background sounds seem to be heard. I cannot imagine a mic not picking up the engine sound as the main background sound. If it is not an engine then something else was repeating at 2200 cpm and only when that mic was transmitting. What could explain that?

Chris- the dictabelt was definitely band limited simply because the medium being used was only slightly more hi-fi than one of Edison's original cylinder recorders. But since its primary purpose was to record speech it was good enough for the task. The near sub-sonic rumble component from a motorcycle engine would likely be filtered out because of this though, leaving only the midrange band to be used for identifying the motorcycle engine. The mic on the motorcycle was almost certainly omnidirectional, as it was designed for function not form, and the police officers surely could not have been bothered with trying to speak on axis into a cardioid mic with everything else they were attending to in the course of their job. The best info I found as far as the dominant frequency of a gunshot puts it at about 800 Hz, which is lower than the 2000 Hz that is commonly considered the dominant frequency of the human voice. The dictabelt is capable of recording either sound, but the waveforms will look different at a high resolution, so I'm hoping to get as good a copy as possible.