Article: 44230 of alt.conspiracy.jfk
Xref: netcom.com alt.conspiracy.jfk:44230
From: 6489mcadamsj@vms.csd.mu.edu (John McAdams)
Newsgroups: alt.conspiracy.jfk
Subject: Re: Proof that Oswald Did Not Shoot JFK
Date: 11 May 1995 23:46:27 GMT
Organization: Marquette University - Computer Services



In article <3oqnnk$lgb@seymour.sfu.ca>, 
schuck@sfu.ca (Bruce Schuck) writes:

>John McAdams [in <009901AB.D3FF0564@vms.csd.mu.edu> on 
9 May 1995 20:41:34 GMT] >

>>
>>
>>I'm afraid Not So Cool Bean is behind the curve on this issue.
>>
>>The "acoustic evidence" was torn apart when peer-reviewed by the
>>Committee on Ballistic Acoustics of the National Research Council. 
>>Their report is in SCIENCE, 8 October 1982.
>
>Wasn't Luis W Alvarez chairman of that committee?
>
>And wasn't he the author of a competing theory?
>
>What a surprise he "tore apart" the acoustical evidence!!!!
>
>>Among the many problems with the BBN and W&A analyses, the most
>>dramatic one is the fact that Sheriff Bill Decker can be heard saying
>>"hold everything" at the time of the supposed "shots."  Since he
>>actualy said that about a minute after the shots were fired in Dealey
>>Plaza, it's obvious that the "shots" W&A picked out where not shots at
>>all.
>
>Nonsense.
>
>Prove they weren't shots by proving they weren't shots.
>

If they came a minute after the shots were fired in Dealey Plaza, they
couldn't be the shots in Dealey Plaza.  There is no reason to believe
they were shots at all.



>If Deckers voice is overlaid over shots then there has been 
>a problem with the recording, such as the needle tracking twice
>or a rerecording problem.
>


The following is from "Reexamination of Acoustic Evidence in the
Kennedy Assassination," Committee on Ballistic Acoustics, National
Research Council, in SCIENCE, 8 October 1982.

    The committee considered seriously the possibility that the
    impulses analyzed by BRSW and WA were overlaid at a later time by
    the "hold everything" message.  Such an overrecording could have
    occurred if the Dictabelt or the recording head was knocked
    backward by about 1 minute in the first minute after the
    assassination, or if a new Dictabelt copy, made by audio coupling
    while a channel II recording was playing in the background, was
    substituted for the original.  The committee concluded that this
    was not the case on the basis of (i) physical examination of the
    Dictabelt for indications of overrecording or of substitution of a
    copy for the original; (ii) the unlikely nature of any of the
    highly contrived scenarios required to provide such an
    undetectable overrecording either accidentally or deliberately,
    (iii) the compatibility of the timing implied by the "hold
    everything identification with other firmly established evidence,
    and (iv) the conclusive acoustic evidence on the Dictabelt itself
    that the cross talk recordings were made through a radio receiver
    with automatic gain control (AGC).  These different forms of
    evidence are all compatible with the recordings being made at the
    same time, and some are incompatible with the hypothesis of later
    superposed recordings by audio or direct electrical coupling. 
    Only the evidence of category (iv) will be reviewed here.

    The digital analyses of the sound spectra can be used to
    demonstrate that the channel II imprint on the channel I recording
    was already present at the channel I receiver and was not added
    later in the recorder or as an overrecording.  The by-radio nature
    of channel II cross talk is demonstrated by its detailed behavior
    in the presence of channel I heterodynes when another channel I
    transmitter is keyed on with a more powerful carrier signal.  The
    frequency offset between the two carriers gives rise to a
    heterodyne tone in the channel I recording.  However, the channel
    I receiver was fitted with AGC to hold the output level
    approximately constant; as a result, the cross talk signals
    decrease in intensity in a few tens of milliseconds (as does any
    residual transmission from the original open microphone).  At the
    end of the channel I heterodyne, the ACG gradually increases the
    receiver gain, and signals on the open-microphone transmission
    increase in intensity in the recording.  An excellent probing
    signal for the channel I gain would be a channel II steady tone
    acoustically coupled from the field loudspeaker to the
    open-microphone transmitter.  This would come in at a constant
    level, and the variation in level on the channel I recorder should
    mimic the ACG action if the channel II signals were present in
    this way.  Inspection of the digital spectrogram (and digital
    tabulations of the data) shows that numerous channel II brief
    tones have a constant level from beginning to end.   A crucial
    demonstration is provided by the channel I heterodyne beginning at
    time 32:02 second in one of the spectrograms.  The underlying
    channel II brief tone is substantially reduced in intensity at the
    beginning of the channel I heterodyne and gradually grows back
    when the channel II brief tone results after the channel I
    heterodyne ceases.  This behavior is validated by similar channel
    II brief tones underlying channel I heterodyne signals in the "You
    want me . . . Stemmons" phrase and in a phrase "I'll check" that
    is also present on both channels.

    Conclusions

    For the reasons discussed above and in its format report, the
    committee on Ballistic Acoustics unanimously concluded that the
    acoustic impulses atrributed to gunshots were recorded about 1
    minute after the President had been shot and the motorcade had
    been instructed to go to the hospital, and that reliable acoustic
    data do not support a conclusion that there was a second gunman.
    (p. 133).


>Prove the recorded sounds were not shots. I dare you.
>
>

See above.   Did you follow that, Bruce?


.John