The HSCA reports failed to prove acoustically that the sounds on the Dallas Police Department (DPD) recording were exclusively from Dealey Plaza or were unique to Dealey Plaza. Some sounds, like that of a carillon bell, either did not originate in Dealey Plaza or were of unknown origin. Finally, the HSCA reviewed no conclusive eyewitness testimony that a DPD motorcycle microphone was stuck open in Dealey Plaza on Channel One and that the information from this particular microphone was being received and recorded at DPD headquarters. In contrast, the NRC report determined that an accurate analysis of the DPD channel recording was extremely difficult due to the inadequate and inaccurate echo analyses performed. HSCA analyses used a subjective selection of impulse peaks, leading to errors in statistical conclusions, and analysis methods that were untested at high levels of background noise. Finally, sound spectrograms and event timing showed that the alleged grassy knoll impulses were recorded on Channel One approximately 1 minute after the actual assassination. A diagram, photographs, and 25 footnotes are provided.