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Rights & Permissions Free Resources PDF EXECUTIVE SUMMARY Display this book on your site! Related Titles Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin Noise and Military Service: Implications for Hearing Loss and Tinnitus Other Related Titles Report of the Committee on Ballistic Acoustics (1982) Commission on Physical Sciences, Mathematics, and Applications (CPSMA) Web Search Builder Use this book's key terms to search within this book, across our collection, or across the Web. Skim This Chapter Skim this chapter and use this chapter's key terms to search within this book. Reference Finder Paste in your own text to find books that relate to your topic. Page 92   E-mail  Facebook  Digg  Stumble  Twitter More Page 92 Front Matter (R1-R4) Executive Summary (1-2) 1 Introduction and Overview (3-7) 2 Description of Studies by BRSW and WA (8-11) 3 Evaluation of BRSW and WA Methodologies and Conclusions (12-17) 4 Timing Evidence from Matching Features (18-31) 5 Evaluation of the FBI Report (32-32) 6 Possible Further Studies (33-33) 7 Conclusions (34-34) Appendix A: Criticisms of Probability Calculations (35-40) Appendix B: Analyses of Sound Spectrograms of Hold Everything... (41-59) Appendix C: Timing of Channel I and II Events (60-80) Appendix D: Possibility of Superposed Recordings (81-88) Appendix E: Siren Sounds (89-91) Appendix F: Possible Further Studies (92-94) Figures (95-112)

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92 APPENDIX F POSSIBLE FURTHER STUDIES This Appendix is written in response to the Committee's assignment to recommend the kinds of tests, analyses, and evaluations needed to obtain better information from the recordings. However, the existence of this Appendix should not be misinterpreted as a Committee recommendation that these tests and analyses should be carried out. If there were to be further studies of the Dallas Police Department Channel I recording in the hope of demonstrating the validity of the conjectured shot from the grassy knoll, the information listed below could be sought. 1. The original Dictabelt could be studied more extensively for possible evidence either for or against the possibilities of the Dictabelt being a copy or containing superposed recordings. No evidence favoring either of these possibilities has so far been found in a physical examination of the belt or in studies of the recording. Further studies could include a careful search on the original belt for a second hum at about 60 Hz which would characterize a copy and an examination of the 60 Hz signal for continuity and possible indications of interceptions. Such studies, however, will now be difficult and may require the constuction of a special drum playback machine for the shrunken and stiffened Dictabelt which now causes marked flutter when it is played back on the normal machine. 2. With the information on the timing of the Channel I recording provided by the cross correlation between Channels I and II discussed in Section IV, the Channel I recording could be examined more carefully for the existence of possible shots in the portion of the recording that corresponded to the time of the assassination (between 65 and 95 seconds on

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93 the BRSW time scale). However, it is unlikely that evidence for shots will be found in that region, since the noise level was much higher there and that portion of the recording has already been examined by BRSW, as described on page 35 of the BRSW report, and no impulse patterns identifiable as gunfire were found; furthermore, there is some evidence that the open microphone was not in the motorcade. 3. There could be an independent analysis following generally the WA procedure but applied to all four of the conjectured shots. In the case of the conjectured grassy knoll shot, it would be of interest to see if the P value for the hypothesis of random locations of impulses cast doubt on that hypothesis. Analysis by the WA method of the impulses attributed to the three Texas School Book Depository shots would be a test both of the method and of this attribution, which contradicts the evidence that the relevant impulses occur approximately one minute after the assassination. If these impulses do fit the hypothesis of three shots, is the open microphone trajectory the same as in the BRSW studies and does it fit with the best limits that can be photographically inferred? 4. The BRSW analysis of the three shots attributed to the Texas School Book Depository could be repeated with a well defined, normalized, and objective selection process for the impulses and echoes to see if the indications of three shots associated with a reasonable microphone trajectory persisted when the unnormalized and subjective selection of impulses and echoes was eliminated. 5. Attempts could be made to see if the reliability of the analyses could be improved by utilizing the availability of amplitude information even though it is recognized that amplitude information can sometimes be misleading. Acoustic spectra and logarithmic Fourier transform studies might help. Unfortunately, one cannot deal with the Dictabelt recording as a faithful reproduction of the sound pressure at the microphone due to the distortion of the radio and recording systems, which include automatic gain control, so it will be difficult to untangle the distortion effect in retrospect. -

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94 6. Independent analyses could be made of the probabilistic calculations both by BRSW/WA and by the present committee, with a critical review of the hypotheses on which the calculations are based. The studies could include the investigation of alternative hypotheses such as other sources of non-random impulse locations and studies of prior and posterior probabilities. 7. A study could investigate means for confirming that the open microphone was actually in Dealey Plaza. This study could examine the recording for the presence and absence of sounds of crowds, the lateness of siren sounds, the possibility of detecting a Doppler shift in the siren sounds, study of the motorcycle sounds to determine if they indicated speeds compatible with the course of the motorcycle presumed by BRSW/WA to have the open microphone, identification of the kind of motorcycle from its sound, cepstral analysis, AGC effects, etc. Bowles2 reports that Officer McLain, after hearing recordings of Channels I and II stated that there was "no way" that his mike could have been the one stuck open. As the present report was about to be printed, Officer Leslie Beilharz (who was not in Dealey Plaza at the time of the assassination) told the Committee chairman by telephone that there was a "good possibility" that his microphone may have been the one stuck open. Additional testimony could be obtained as to the location of the open microphone and attention should be given to the many questions raised in the report of James C. Bowles, including those on the microphone location. 8. A detailed analysis could be made of the interpretation of the more than 200 millisecond time displacement between the conjectured shots of the BRSW and the WA studies. 9. The Zapruder film could be analyzed further to see if the apparent incompatibility between the conjectured shots and the data inferred from the camera's angular accelerations can be removed.

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