The HSCA’s Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination Michael T. Griffith 2021 @All Rights Reserved Sixth Edition Contents Introduction The NRC Panel The Motorcycle with the Open Microphone No “Audible” Shots on the Dictabelt Tape How Could the Grassy Knoll Shot Have Missed? Crowd Noise and the Carillon Bell The Decker “Hold Everything” Crosstalk Larry Sabato’s Sonalysts Study The Grassy Knoll Shot and the Zapruder Film Five Gunshots on the Dictabelt Tape? A Summary of the Acoustical Evidence Bibliography Introduction In 1978, the House Select Committee on Assassinations (HSCA) announced that a police dictabelt recording made in Dealey Plaza during the John F. Kennedy (JFK) assassination contained four impulse patterns caused by gunfire, that one of the shots came from the famous grassy knoll, and that two gunmen were involved. This stunning development meant that the Warren Commission (WC) erred in claiming that only three shots were fired at President Kennedy and that only one gunman was involved. When the HSCA acquired the police dictabelt recording, the committee hired the prestigious scientific firm Bolt, Beranek, and Newman (BBN) to analyze the tape. BBN had experience with doing acoustical analysis. After BBN completed their analysis, the HSCA asked two acoustical scientists from the Queens College Department of Computer Science, Dr. Mark Weiss and Mr. Ernest Aschkenasy, to review the BBN research. The HSCA selected Weiss and Aschkenasy because they were recommended by the Acoustical Society of America. Richard Trask explains how the tape initially came to the attention of the HSCA and then describes the analyses that were performed on it: The original recordings of these transmissions, made over two separate police radio networks, were located in the possession of a Dallas official. Police transmissions had been recorded on Department Channel 1 by means of a 1 The HSCA’s Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination Dictaphone belt recorder and the day of the assassination this channel was used primarily for normal police activities. Channel 2 was used that same day as a communications link for the presidential motorcade. It was voice-activated and recorded on a Gray Audiograph Disk at headquarters. Though Channel 2 was apparently not in use during the period when the actual assassination occurred, by a fluke of a microphone transmitter on a motorcycle or other vehicle being stuck on the "On" position, approximately 5.5 minutes of the noises in and around the vehicle were recorded by the Dictaphone belt, including around the time of the shooting. Though unclear to the unaided ear what the various noises recorded on the Dictabelt meant, several critics postulated that among the clatter were a number of possible gunshots. The Committee decided to give this problem over to acoustics experts. These respected acoustics scientists would analyze the nature and origin of the suspect sound impulses on Channel 1 to determine if sounds of shots had been recorded; and if so, how many, the time interval, and point of origin. In May 1978 the Committee contracted with Bolt, Beranek and Newman, Inc. to attempt the analysis. By means of sophisticated and, to the layman, complicated scientific analysis of the recordings, chief scientist Dr. James Barger located 6 impulse sequences which could have been caused by a loud noise such as a gunshot. The Committee was urged to conduct an acoustical reconstruction of the assassination at the Dallas site. Realizing that Barger's initial findings, if true, pointed to a probable assassination conspiracy, the Committee sought an independent review of his analysis by Queen's College, New York, professor Mark Weiss and his research associate, Ernest Aschkenasy. Barger's analysis and methodology for the reconstruction were concurred by the two others, and on August 20, 1978, an elaborate test in Dealey Plaza was conducted. Three of the impulses matched an origin point at the Texas School Book Depository sixth floor, and one impulse, the third in the sequence, matched an origination point on the grassy knoll. Asked by the Committee to further study Barger's work to obtain more certain results of his possible grassy knoll shot, Weiss and Aschkenasy put together an analytical extension to refine the estimate. They studied Dealey Plaza determining which structures were likely to have caused echoes received by the microphones. By identifying these echo-generating sources around the vicinity of the knoll, there were able to predict what "sound fingerprints" would have been created by a shot from the grassy knoll location when picked up by an open microphone. Each location of a microphone relative to a shooter's location would, by echoes generated off constant structures, produce a unique sound travel pattern which they referred to as a "sound fingerprint." The experts were confident that their precise calculations, taking numerous variables including air 2 The HSCA’s Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination temperature in 1963 and buildings structured after 1963 into consideration, gave them a certainty factor of 95 percent or better, that impulse number 3, previously identified by Barger, was in fact a shot fired from the grassy knoll. (Trask 131- 132) 1. Texas School Book Depository 2. Dal-Tex Building 3. County Records Building 4. Houston Street 5. Elm Street 6. Grassy Knoll 7. Triple Underpass 8. Main Street Dealey Plaza, Dallas, Texas David Scheim, who holds a doctorate in mathematics from the Massachusetts Institute of Technology, discusses the dictabelt and its validity as proof of multiple gunmen: Eleven years later, in March 1978, the House Select Committee on Assassinations located a trunkful of 1963 vintage Dallas Police records. Among them was a dictabelt recording of “channel one” transmissions by police on the day of the JFK assassination. And on the dictabelt was a ten-second series of loud clicks and pops transmitted from a police motorcycle whose microphone control button had stuck in the “on” position. Moreover, recorded time annotations fixed the time of the sounds at seconds after 12:30 p.m.—just when the shooting occurred. Indeed, there were important additional elements that corroborated the conclusion of Barger, Weiss and Aschkenasy. The positions they determined for the motorcycle at the time of the four shots traced out a path on Houston Street that fit the actual course and speed of the motorcade. Moreover, an "N- 3 The HSCA’s Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination wave," characteristic of supersonic gunfire, appeared in each dictabelt impulse for which the police microphone was in an appropriate position to detect it, including the recorded sound of the third shot [identified by the Committee as coming from the grassy knoll]. The most striking find, however, was the exact location of the grassy knoll gunman. According to the acoustical calculations, this firing position was behind the picket fence, eight feet west of the corner. That was just two to seven feet from where S. M. Holland, a dozen years earlier, had placed the signs observed by himself and fellow railroad workers: the puff of smoke, muddy station wagon bumper, cigarette butts, and a cluster of footprints. (Scheim 25-26, 28, original emphasis) Dr. G. Paul Chambers, a physicist who has worked with NASA, with the Naval Surface Warfare Center, and with the Naval Research Laboratory, explains some of the intricate correlations between the dictabelt impulse patterns and the impulse patterns from the Dealey Plaza test firing: The HSCA commissioned the acoustics firm of Bolt, Beranek, & Newman (BBN) to perform a scientific analysis on the Dictabelt recording. This firm had previously successfully utilized acoustical analysis to determine the events that transpired during the Kent State shooting in 1970. Their acoustical analysis was later used as evidence presented to a grand jury to determine which national guardsman had fired first. BBN was also pointed by Judge John J. Sirica to serve on a panel of technical experts to analyze President Richard Nixon’s Watergate tapes. Led by their chief scientist, Dr. James Barger, BBN converted the sounds on the tapes [the Channel 1 tape and the Channel 2 tape] to digitized waveforms. They then ran the waveforms through electronic filters to eliminate repetitive background noise like the sound of the motorcycle pistons firing. The firm then examined the processed waveforms for “sequences of impulses.” Their analysis indicated that there were six sequences of interest, spaced together within an eleven-second period recorded on channel 1, which could be consistent with the sounds of gunshots. Weiss and Aschkenasy reviewed Barger’s analysis and conclusions. They found that Barger’s analysis was valid and his conclusions supported by the evidence on the tape. They concurred with his recommendation to conduct live-fire tests in Dealey Plaza to determine the origin and direction of the gunshots, and they approved his plan for acoustical reconstruction. In Dealey Plaza, the sounds of gunshots would produce similar echoes. When recorded and captured on a specialized electronic device like an oscilloscope that converts sound patterns into pictures, these echoes appear as “acoustical waveforms” and appear as unique signatures of sound-producing events. In the case of a rifle shot in Dealey Plaza, the acoustical signatures would differ based on the origin, direction, and velocity of the shot, as well as the location of the 4 The HSCA’s Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination recording microphone. The echo patterns would depend on the timing of sound reflections off building or other structures and obstructions in the plaza. A recording was made of the sounds received at each microphone during each test shot, making a total of 432 recordings of impulse sequences.