Studies & Articles

House Select Committtee on Assassinations: BRSW (BBN) 1979

In order to analyze the Dictabelt recording, the HSCA engaged the services of a team from Bolt, Beranek, and Newman (BBN), a leading acoustics consulting firm, led by James Barger. They tried to identify possible gunshot impulse patterns, and determine the origin of the sounds. Their analysis concluded that there was a 50% chance of a fourth shot, fired from the Grassy Knoll.

BRSW: Report to the HSCA

House Select Committtee on Assassinations: Weiss & Aschkenasy (W&A) 1979

Since a 50% chance was inconclusive, the HSCA turned to Mark Weiss & Ernest Aschkenasy, from Queens College. They were asked to review the data and find a way to refine the results. Weiss & Aschkenasy (W&A) plotted echo paths on a survey map of Dealey Plaza, picking echo producing objects on the map by referencing the test shot recordings, and comparing projected echo times from the map to the dictabelt signals. They claimed with a 95% certainty that there was a shot from the Grassy Knoll.

W&A: Report to the HSCA

James C Bowles: The Kennedy Assassination Tapes - A Rebuttal to the Acoustical Evidence Theory 1979

James C Bowles was the Communications Supervisor of the Dallas Police Department at the time of the assassination, and later became Dallas County Sheriff. After the HSCA he wrote this article to rebut the committee's findings.

Bowles: The Kennedy Assassination Tapes

National Research Council: Committee on Ballistic Acoustics 1982

Having reached its conclusion, and its term ending, the HSCA asked the Justice Department to pursue the case. The Justice Department requested that the National Research Council (NRC), part of the National Academy of Sciences, review the acoustic evidence. In 1982 the NRC Committee on Ballistic Acoustics, headed by Norman Ramsey, released their report and a version of that report was published in Science. The NRC report disputed the statistical significance of the HSCA findings, and following a suggestion from Steve Barber, proved that there is an instance of crosstalk on channel I at the time of the alleged shots.

CBA: Report of the Committee on Ballistic Acoustics (Full Report)
CBA Article in Science: Reexamination of Acoustic Evidence in the Kennedy Assassination

Agarwal, Garwin, Lewis: IBM Report 1982

Separately, one of the CBA members (RL Garwin) produced a research report with his colleagues (RC Agarwal, BL Lewis) at the IBM T.J. Watson Research Center. Studying the effects of heterodynes in the recordings, it established that the "bell" sound was not actually a bell, and that the Decker crosstalk was recorded live on channel 1 and couldn't have been picked up or overdubbed at a later time.

IBM: Signal Processing Analysis of the Kennedy Assassination Tapes

Barber: Double Decker 1989

Steve Barber wrote an essay about his experience.

Barber: Double Decker

DB Thomas: Science & Justice 2001

A Dallas Police Department recording contemporaneous with the Kennedy assassination contains five impulsive sounds that have the acoustic waveform of Dealey Plaza gunfire. One of the sounds matches the echo pattern of a test shot fired from the Grassy Knoll. The shock wave precedence associated with this pattern is consistent with the muzzle velocity of a .30 calibre rifle. Criticism of the acoustic identifications on statistical grounds is based on erroneous assumptions concerning the assignment of values to the parameters that determine the probability that random noises could resemble gunshot patterns. A conservative estimate of the true value of the probability that the putative Grassy Knoll shot is attributable to random radio noise is no greater than 0.037. Alleged asynchroneity of the sounds with the time of the assassination stemmed from several incorrect assumptions. Whatever their origin, the gunshot-like sounds occur exactly synchronous with the time of the shooting.

DB Thomas: Echo correlation analysis and the acoustic evidence in the Kennedy assassination revisited

O'Dell: Acoustic Evidence in the Kennedy Assassination 2003

When the Thomas article was published this author (Michael O'Dell) began reviewing the previous work. I was fortunate to encounter into Johann Rush, who provided me with old tape copies of the police recordings. Meanwhile, some former members of the CBA decided to revisit the issue and work on a response to the Thomas article.  Steve Barber put me in touch with them and they provided me with digital copies of the recordings from the files of the CBA.

O'Dell: Acoustic Evidence in the Kennedy Assassination

Berkovitz: Searching For Historic Noise 2003

A new analysis of the recording, with various steps carried out automatically, has produced different results. Among these are statistical results indicating that the gunfire noises are not unusually different from other noises in the recording; spectral data on background noise demonstrating that the noise is not the kind expected from motorcycles or other types of moving vehicles; and, analysis of fluctuations of level in the recording indicating, as earlier work has already shown, that the noises said to be assassination gunfire were recorded during a voice transmission that was made after the assassination.

Berkovitz: Searching For Historic Noise

Linsker, Garwin, Chernoff, Horowitz, Ramsey: Science & Justice 2005

The former CBA members along with Dr. Ralph Linsker of IBM, published their article in "Science & Justice" in 2005.

Linsker et al: Synchronization of the acoustic evidence in the assassination of President Kennedy

Sonalysts: The Kennedy Half Century Acoustical Analysis 2013

Abstract — The open microphone transmissions of a Dallas Police Department motorcycle officer's radio are of continuing interest among assassination researchers. If the motorcycle was in the motorcade then it may have detected and transmitted the sounds of gunfire. This study examines features of the recording that have not been rigorously measured until now. Novel methods were applied in order to measure motorcycle engine speed versus time so that it might be compared with the known movements of the motorcade. Detailed analyses of other sound artifacts were also performed. The evidence obtained suggests that the motorcycle was not part of the motorcade and therefore was not in a position to record the sounds of gunfire.

Sonalysts: The Kennedy Half Century Acoustical Analysis

Thomas: Sabato Sonalysts Sophistry 2013

Don Thomas criticizes the work done by Sonalysts.

Thomas: Sabato Sonalysts Sophistry

Sonalysts: Further Research, Analysis, and Commentary 2014

In response to Dr. Don Thomas’ essay, “Sabato, Sonalysts, & Sophistry,” the Sonalysts’ team revisited its analysis for Larry Sabato’s book, “The Kennedy Half Century.”1,2 Dr. Thomas states that our conclusions overlooked pertinent evidence and erroneously interpreted the data. Our intent with this paper is to clarify and reaffirm our conclusions.

Sonalysts: Further Research, Analysis, and Commentary 2014