ACOUSTICS
In 1978 the acoustics firm Bolt, Beranek
and Newman (BBN) analyzed a tape recording made of the Dallas Police Department
(DPD) channel one. On August 20, 1978 BBN performed a test in Dealey Plaza
by shooting several shots from two locations at targets placed on Elm Street
in approximately the positions the limousine was at the time of three likely
shots. The test shots were recorded by microphones placed on Houston Street
and Elm Street which matched the route of the motorcade. In September 1978
BBN testified to the HSCA that it had compared the test shots to the DPD
tape and found four shots on the DPD tape. But one of the four matches
was the most controversial, a shot from the grassy knoll, and BBN only
gave it a 50-50 chance of really being a shot from the grassy knoll. So
HSCA hired two acoustical experts, Weiss and Aschkenasy (W&A) to resolve
the uncertainty of the grassy knoll shot. W&A identified the echo paths
of the grassy knoll shot and stated with a confidence of 95% or better
that one of the four shots was fired from the grassy knoll. The HSCA ended
at the beginning of 1979 and no further work was done on the acoustical
evidence by the HSCA. However, the HSCA suggested that more work should
be done, but the DOJ refused to do so. Instead, it assigned the National
Academy of Sciences (NAS) the task of refuting the HSCA acoustical analysis.
In May 1982 the NAS panel issued a report claiming that there were no shots
on the DPD tape. In August 1983 I wrote a Rebuttal
to Ramsey which points out many errors in the NAS report, and reaffirms
the accuracy of the HSCA studies.
In the late 1980's I wrote some BASIC programs
on the Commodore which simulate the HSCA acoustical analysis. One of the
first programs was a test of method which analyzes three BBN test shots
in order to identify possible echo producing objects and test the calculation
process. I have converted it to QBASIC for the IBM and included it in the
file named BBNstudy.bas .
The other program simulates the W&A study by searching for matching
echo patterns for each DPD tape impulse. It is converted to QBASIC and
included in the file named DPDstudy.bas
.