For readers who want to learn more about the HSCA acoustical evidence of multiple gunmen, I should have already mentioned Dr. G. Paul Chambers' superb chapter on the acoustical evidence in his book Head Shot: The Science Behind the JFK Assassination (New York: Prometheus Books, 2012), chapter 6. Believe it or not, until earlier today, I had completely forgotten about Dr. Chambers' chapter on the acoustical evidence! That's what can happen when you take a several-years-long break from a case!
Dr. Chambers is an internationally recognized expert in the field of shock physics and has performed extensive high-speed photographic studies of high-velocity impacts and deformations of solids as well as computer modeling of shock wave and matter interactions. He has worked as a research scientist/research director at NASA, with the Naval Surface Warfare Center, and with the Naval Research Laboratory.
Chapter 6 is 21 pages long. In it Dr. Chambers explains the acoustical evidence in clear, understandable terms. He explains the nature and importance of the correlations between the dictabelt and the Dealey Plaza test firing much better than do the HSCA materials. Frankly, he explains the correlations even a bit better than Dr. Thomas does. He also reviews the NRC panel's report and the Watson Research Laboratories' report and finds them unconvincing and contradictory, and he notes that they evade dealing with the powerful correlations between the dictabelt impulse patterns and the test-firing impulse patterns.