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The Robert F. Kennedy Assassination: The Acoustics Evidence

Some years following the assassination of Senator Robert F. Kennedy at the Ambassador Hotel on the night of June 4/5 1968 critics of the official version of the assassination said there were audio recordings of more than 8 shots fired when RFK was shot. Such conclusions, if correct, would have established that more than one gunman had been firing because the assassin’s gun could not hold more than 8 bullets. These claims of extra shots fired originated from television recording equipment located in the rear of the Embassy Ballroom of the Ambassador Hotel, the scene of Robert Kennedy’s California Primary election victory speech.

In his important book about the RFK assassination, The Killing Of Robert F. Kennedy (1995), veteran crime reporter Dan Moldea identified ABC News as the only television network broadcasting when the shooting began. Both Andrew West of Mutual Broadcasting and Jeff Brent of Continental Broadcasting were also recording but switched on their microphones after the shooting began.

Moldea wrote, “In November and December 1982, these three audio sound recordings were subjected to scientific, but controversial, acoustical analysis, in an attempt to determine if a distinctive gunshot ‘audio signature’ can be identified and the number of gunshots counted. According to Dr Michael H.L. Hecker – an electrical engineer with the Stanford Research Institute in Menlo Park, California – who conducted the tests, ‘On the basis of auditory, oscillographic and spectrographic analyses of these three recordings, it is my opinion, to a reasonable degree of scientific certainty, that no fewer than 10 gunshots are ascertainable following the conclusion of the Senator’s victory speech until after the time Sirhan Bishara Sirhan was disarmed.’ ”

In the 1980s I was given an opportunity to examine an audio copy of the ABC tape. A writer by the name of Robert Cutler had sent me the tape and I was asked to determine if any shots were audible. At that time I believe I was told I might hear balloons popping, and not to confuse this with gunshots. After examining the tape I wrote Cutler back and told him that I couldn’t hear anything except what could possibly be balloons being popped and that I could hear where the recorder was turned off and then back on in spots, but that I couldn’t determine whether or not with certainty that there were gunshots.

In 2006, British author Mel Ayton, who has written books on the JFK and Martin Luther King Jr. assassinations, sent me an audio tape recording of live broadcasts made at the Los Angeles Ambassador Hotel which had been compiled by JFK researcher and author Larry Sneed. The tape is a collection of the live news broadcasts on the night RFK was shot; none of the recordings were made in the pantry. Part of the compilation contains the broadcast made by ABC News, which was stationed in the Embassy Ballroom. After making a more thorough examination of the ABC tape I concluded that the recording was obviously made AFTER the shooting. The vocal contents of the pandemonium going on during the segment of the tape proves this. The screaming and shouting of people are those of panic stricken individuals who were reacting to the apparent gunshots. The sounds that I heard which suggested gunfire were nothing more than the sounds of the microphones held by the person recording the pandemonium, bumping either into things with it, or fumbling around with it, or something of that nature. They do not resemble gunfire at all. I concluded that the ABC tape was absolutely worthless.

In order to carry out further research on these recordings Mel Ayton asked if I would work with Michael O’Dell who also had experience in acoustics research. I first became acquainted with O'Dell in 2001. O’Dell was a technical analyst who, from 2001 through 2005, worked with a committee of leading scientists when it reexamined the acoustics evidence in the JFK assassination. The committee included Norman F. Ramsey of the original CBA committee that I had worked with, during the period 1980-1982. O’Dell stated, “…I don’t believe any shots were captured on the ABC tape.... I think (the ABC tape) is worthless....”

In early 2006 Ayton, who had been writing a book on the controversy over the assassination of Robert F. Kennedy, discovered from one of his sources in the United States that there was a tape recording located at the California State Archives (CSA) that supposedly captured the actual gunshots as they were fired at Kennedy and that the recording was the only one in existence that captured the shooting from beginning to end. The recording was made by a freelance reporter, Stanislaw Pruszynski, on the night of June 4th 1968. Pruszynski told the Los Angeles Police Department his cassette recorder was running all through the shooting.

The CSA records describe the tape as : “Pruszynski, Stus - At Ambassador Hotel on June 4th; tape is his recording of events at the hotel. Includes end of RFK’s speech, possible shots being fired, post-shooting hysteria in kitchen, and interviews with a man who claims Sirhan was not alone. Pruszynski narrates what he is seeing.” The tape was eventually lodged with the California State Archives. (The tape is mentioned in the California State Archives lists of the Investigation Records Audio Tapes, Appendix E.CSA-K123 I-4837 June 4-5 1968.)

Mel Ayton asked me if I had knowledge of the tape recording and I replied in the negative. My initial reaction was that the “Pruszynski Tape” was probably not going to reveal anything more than the CBS and ABC tapes, which as stated before, revealed nothing but a lot of crowd noise, and what sounded like microphones banging into objects, and/or balloons popping here and there.

Ayton asked the California State Archives to send me a copy of the tape recording. Later he was able to obtain a digitized copy of the recording and it was mailed to me. As I was working on the CSA Pruszynski audio cassette tape and the Pruszynski Tape digitized version, Moldea told Ayton that he had earlier been approached by a CNN journalist, Brad Johnson, who had told Moldea about the Pruszynski Tape.

Among his hundreds of interviews about this case, Moldea had spent fourteen hours with Sirhan Sirhan and believed that the convicted assassin had murdered Senator Kennedy and acted alone. Despite Johnson’s enthusiasm for this new discovery, Moldea was skeptical, insisting that only eight shots had been fired and that Sirhan had fired all of them.

During the Spring of 2006, I worked on the Pruszynski Tape with the assistance of Dr. Chad Zimmerman, a researcher who had some experience in examining the scientific aspects of the JFK assassination, and Michael O’Dell. After months spent examining the tape I concluded that I could not be certain that I hear more than seven shots. I heard what might have been the eighth shot, but couldn’t be absolutely certain at that point. The sound that may be the eighth shot appears just a millisecond before the sound of a very high pitched scream made by a female in or near the pantry.

Michael O’Dell was in agreement with my findings but stated, “I still have a lot of uncertainty about how many shots are clearly identifiable on the Pruszynski Tape. Right now I’m willing to identify six for certain. But of course the real question is whether there is solid evidence for more than eight. I certainly don’t see how anyone can use it to claim more than eight and that’s the main point.”

Chad Zimmerman examined the tape using computer software. Zimmerman stated, “I ran the audio through an analysis program, which provided [an] audio analysis. I took two different graphs and split them apart, enhanced the second to a different color then overlayed them with 50% opacity.

 The gunshot ‘signatures’ from the ‘Pruszynski Tape’ – spectogram by Dr Chad Zimmerman. Each spike on the graph represents a gunshot by a .22 caliber weapon. The ninth spike has been identified by Steve Barber as a woman (possibly Ethel Kennedy) screaming ‘Aahhhhhhhhhh! I think my husband’s been shot!’.

You can see eight spikes that correlate to the audio gunshots. The last occurs just before the scream. However, I don’t think one can necessarily say that more shots couldn’t have existed after that point, but that they would have been drowned out by the scream. However, in my opinion, there are only eight, .22 caliber gunshots heard on that tape. Now, preceding these eight, I hear one deeper audible ‘pop’ just prior to the eight shots in rapid succession. However, this is a bit longer and deeper, which sounds more like a balloon pop than a gunshot….My only real contribution here is the spectrographic run that I did, which showed 8 spikes. [My conclusion is] 8 or fewer shots are heard and none would be a .38.” With regard to the possibility that RFK could have been shot by security guard Thane Cesar, who carried a .38 caliber pistol, Zimmerman said, “…there certainly isn’t a .38 shot on [the] tape.” Both Chad Zimmerman and I also agree that the conspiracy writers’ No. 1 suspect as the ‘second gunman,’ Thane Cesar, could not possibly have fired his .38 revolver. (Moldea, who had also interviewed Cesar dozens of times, had concluded in his book that Cesar, who passed a lie-detector test that Moldea had arranged, was an innocent man who had been wrongly accused.)

There are three sounds which take place approximately 1 second before the string of shots fired from Sirhan’s weapon. Chad Zimmerman and myself identified one of them as a “deeper toned pop,” meaning that it doesn’t have the same popping sound as the string of 7 or 8 shots fired from Sirhan’s weapon. The sound which precedes the “deeper toned pop” is very difficult to reach a conclusion as to what, exactly, it is. I believe that the two sounds are connected to each other, physically, but that neither of them are gunshot sounds.

Brad Johnson’s chronology of events of the Pruszynski tape, refers to one of these sounds as a “mysterious thump.’’ I will refer to the Johnson “mysterious thump” as sound #1, and the “deeper toned pop” as sound #3. I do not know which of the two sounds he considers the “mysterious thump,” but will assume that it is sound # 1. There is also a peculiar sound that occurs between sounds 1 and 3, which I refer to as “sound #2.”

Sound #1 bears the resemblance of a microphone bumping into something solid, producing a tone that resonates briefly. There is the sound of an audible bassy-type “click," when the digital version of the Pruszynski recording is played. One can actually feel a “thump” emanating from the speakers. I noticed that the “thump” is not as pronounced on the cassette copy.

Sound # 2 is a sound akin to someone running their finger up the lowest (or thickest) of the guitar strings on a guitar, which makes a sound such as “zzzziiip." Simultaneous with the “zzziiip" sound, a female voice can be heard saying something indecipherable, that rhymes with the word “Tuesday." These sounds are joined together, and one is left with the impression that the sound may be an appliance in the pantry turning on. There was a very large ice machine in the area where the shooting took place, which Sirhan was hiding behind, before he began shooting. It could have been an exhaust fan, or ventilator turning on.

Sound # 3. This section of the recording peaked my interest, because I am reasonably certain that some will try to claim that sound #3 could be gunfire from a different weapon and not fired by Sirhan.

Soon after I began studying the Pruszynski tape, I decided that I would be able to obtain more accurate results using my computer. I transferred the tape onto my computer hard drive, and used a tool on my computer which allows me to slow down a recording to a crawl without changing the pitch of the of the recording. When I slowed sound #3 I noticed that it didn’t make a singular sound, rather, it contained a double sound giving the impression that it contained echo. When played at true speed, however, the double sound cannot be detected by the human ear. None of the shots fired from Sirhan’s gun produced an echo-type sound, nor did the voices of the people in the pantry who were shouting. I can’t rule out echo altogether, but, it seems odd that this sound alone produced a double sound that can only be detected when the recording is slowed, but none of the voices or string of shots produced an echo.

My first instinct was that since there were two swinging doors that led to the kitchen where Senator Kennedy was shot, it is possible that sound #3 is one of the two doors being pushed open and banging into the wall. Sometimes, when someone is pushing a door open, they keep their hand on the door all the while pushing on it while it hit’s the wall. Once it hit’s the wall, and with the hand still pushing on the door, the door bounces off the surface of the wall, then back again, causing a second “thump’’ when it hits the wall a second time. This is something that can easily be demonstrated. The sound does not sound like a gunshot to me.

I would like to add that, after listening to the sounds very carefully, it is my conclusion that these sounds are not in the same location as Sirhan, who fired the 7or 8 gunshots. They seem to have slightly less volume than the string of 7 or 8 gunshots heard on the tape. This, to me, lends more support to the conclusion that if a .38 caliber weapon was fired from within the same location as Sirhan, the sound of the shot would be much louder since it was suggested it was a .38 caliber weapon, which would create a higher level of sound, than that of a .22 caliber.

Furthermore while listening to a gentleman talking with Pruszynski, he actually stated that the shots ‘weren't very loud,’ and he thought the sounds were a 'Chinese type of fireworks.' This, to me, certainly adds to the fact that no .38 caliber weapon was fired.

Whatever sound numbers 1 and 2 are, they do not bear any resemblance to a .38 caliber hand gun.

In 2006, Mel Ayton asked a British acoustics firm, JP French Associates, to examine the Pruszynski Tape. Using state-of-the-art acoustics computer-based technology Philip Harrison, a JP French Associates acoustics expert, who was given the task of examining the tape, wrote a report for Ayton (appended to his book The Forgotten Terrorist). I worked closely with Philip Harrison and forwarded to him my analysis of the tape. Harrison looked at what information I had discovered and listened to those things I pointed out, before compiling his own analysis. Harrison’s report decisively concluded that only eight shots were fired in the pantry of the Ambassador Hotel. Harrison’s findings were examined and verified by Professor Peter French, visiting professor at the University of York. Professor French is an expert in the analysis of digital and magnetic recordings.

The "High Pitched Scream

Within a millisecond of what appears to be the final gunshot, there is a high-pitched female scream coming from within, or near the pantry.

After the blood curdling scream “AHHHHH!” the woman continues, saying, “I think my husband's been shot!” I believe that this may have been Ethel Kennedy, the Senator’s wife, who was not in the room when the shooting occurred. As the crowd reacts to the shooting, the woman is screaming "Back…No! “Get back...get back!’ These are the last words picked up by Pruszynski’s microphone of the woman at this point, probably due to her rushing to aid her husband.

We do not know where Pruszynski was located when he captured the shooting. If the woman is Mrs. Kennedy, I believe that she holds the key as to just where Pruszynski was standing with his recorder In order for her voice to be so distorted, she had to be standing within inches of the microphone.

Interestingly, immediately after the woman whom I believe to be Mrs. Kennedy, screams, “AHHHHHH! I think my husband's been shot!“ a distinct male voice utters the word “How?” I determined the voice to be that of Mr. Pruszynski by comparing this voice with Pruszynski's as he is interviewing witnesses about 20-25 minutes after the shooting on the tape.


In correspondence with Dan Moldea and me, CNN reporter Brad Johnson alleged that the Pruszynski Tape contains evidence of more than eight shots fired in the pantry of the Ambassador Hotel.

Working with Philip Harrison, we had an opportunity to respond to the claims made by Johnson.

The CNN journalist had told Moldea in 2005, “After having listened to this recording many times over a number of months, I believe that I am hearing 10 shots as follows: 2 shots fired in quick succession and then a string of 8 shots fired in quick succession. An acoustics expert here in Atlanta has just issued a confidential report on this recording that concludes there are 9 high-probability gunshots captured in this tape (one less than what I believe I'm hearing, but one more than Sirhan Sirhan could have fired).”

Brad Johnson and his purported acoustics expert had matched the Pruszynski Tape to some CBS footage and counted 11 shots. Johnson provided Moldea a timeline in which he stated:

12:16:00.5 am PDT - The first shot or shots are fired in the kitchen pantry (to my hearing, there are two shots being fired in quick succession at this time but presently an examination of my acoustics expert can confirm the high probability of only one shot).

12:16:01.0 am PDT - A mysterious "thump" sound is heard but at this point in my research it appears unlikely this sound was a gunshot.

12:16:04.0 am PDT - By this time, a string of eight additional shots have been fired (all eight are high probability shots according to my acoustics expert). Our count of high-probability gunshots is now 9.

12:16:05.0 am PDT - A long, very high-pitched female scream is heard in the kitchen pantry.

12:16:18.5 am PDT - Andy West turns his tape recorder back on, upon entering the kitchen pantry (his recorder has been off for the past 66.5 seconds).

12:16:55.0 am PDT - Two more high probability shots are fired as a struggle with Sirhan Sirhan continues for his handgun (since Sirhan emptied his weapon, these could have been the last two bullets discharged as a result of the struggle). Our count of high-probability gunshots is now 11.

12:17:41.0 am PDT - Andy West shouts into his microphone, "Ladies and gentlemen, they have the gun away from the man.”

Harrison responded to the timeline by stating:

According to the timeline created by [Brad Johnson] there is a period of 50 seconds between the ‘long, very high-pitched female scream’ and the ‘two more high probability shots … fired as a struggle with Sirhan Sirhan continues’. If his timings are correct then these events have not been captured on the Pruszynski recording. In terms of elapsed time the corresponding point on the Pruszynski recording is approximately 14 seconds into the interview with the man where ‘negroes’ are discussed. However, if [is] timings are wrong and the events he is referring to are those identified by Steve [Barber] that occur at 6:00 and 6:01 on the CD then I cannot agree that they are gun shots. Firstly, the two sounds have very different auditory qualities. The first sound gives the impression that it occurred quite close to the microphone and could be described as a ‘light tap’, whilst the source of the second sound appears to have been further away. Neither of the two sounds shows any significant auditory or spectrographic similarity to either the 7 identified shots or the unknown sounds preceding them. Spectrographic analysis of the second sound at approximately 6:01 shows a clear ‘double impulse’ structure. The two impulses are about 20 milliseconds apart. This configuration is not found in the earlier section of the recording where the shots occur. As stated before it is not possible to accurately identify what these two sounds are but there is no evidence within the recording to support the claim that they are both shots.

My findings are in agreement with Harrison’s. In examining Johnson’s claims I looked at the CBS news coverage and I was able to synchronize the film footage with audio to the Pruszynski tape, of the moment in question after the shooting. I concluded with 100% certainty that there are NO extra gunshots on the Pruszynski recording. They do not appear on the CBS footage, which is being shot just inches from where Senator Kennedy is lying on the floor, which would put the cameraman within only feet from where Sirhan would have been apprehended. I timed the section at the beginning of the Pruszynski Tape, and it adds up to approximately 16 seconds. This is the section during the wrestling with Sirhan, where you can hear a man yelling, ‘Break his hand...break his hand’ and scuffling in the background. Within this 16 seconds of audio, I hear nothing resembling gunfire.

This new acoustics evidence in the RFK case suggests to a high degree of probability that on the night of June 4/5 1968 in the Ambassador Hotel pantry there were no other gunmen who fired shots at Senator Kennedy. Furthermore, this evidence negates to a high degree of probability the allegations by conspiracy advocates that extra bullets were either discovered or retrieved from the pantry’s swinging doors.