If the acoustic evidence is so solid, why didn't anybody see a gunman on the GK?
Umm, because he fired from a concealed position behind the fence on the knoll.
Moreover, as I have pointed out to you before when you have argued against a grassy knoll shooter:
-- Several witnesses saw gun smoke coming from the area behind the fence on the knoll identified by the acoustical evidence as the location of the gunman.
-- We have hard photographic evidence that confirms the eyewitness accounts of seeing gun smoke on the knoll, i.e., the Wiegman film, which shows a small cloud of smoke hanging in the air near the fence on the knoll.
-- Several witnesses smelled the pungent odor of gunpowder on and near the knoll right after the shooting.
-- Two witnesses saw a man running from the grassy knoll into the railroad yard seconds after the shots were fired.
-- Dozens of witnesses in the plaza (at least 58) said they heard shots fired from the grassy knoll.
We still see lone-gunman theorists repeating the argument that those witnesses merely heard echoes of the sixth-floor gunman's alleged three shots. In his superb 1998 book
Cover-Up, mathematician Stewart Galanor explains why the echoes argument is invalid:
Echoes are caused by sound bouncing off large, hard surfaces. . . . There are no buildings on the knoll or overpass that would have reflected sound back to confuse witnesses in Dealey Plaza. Beyond the knoll the terrain is flat with railroad tracks, while the knoll is covered with grass, shrubs, and trees that absorb sound. If there were any echoes, they would have been caused by the sound of rifle fire from the knoll echoing off the Book Depository (Cover-Up, p. 76).-- Dozens of witnesses rushed up the grassy knoll right after the shooting because they believed shots came from there.
-- Seconds after the shooting, Sheriff Bill Decker ordered his officers to seal off the area of the railroad yard behind the knoll and the triple underpass: "Have Station 5 to move all men available out of my department, back into the railroad yards there in an effort to try to determine just what and where it happened down there, and hold everything secure until the homicide and other investigators can get there."
-- Seconds after the shooting, Chief Jesse Curry ordered his officers to check the area of the triple underpass: "Get a man on top of that triple underpass and see what happened up there!"
-- William Newman, a combat veteran, said he heard a shot come from behind him on the knoll and that he heard the whiz of the bullet as it passed near him. As someone who heard bullets whiz above him in the Army, I know exactly what Newman was describing.
-- Abraham Zapruder, before he knew what he was supposed to say, told the Secret Service on 11/22/63 that "the position of the assassin was behind Mr. Zapruder" (CD 87). Zapruder was standing on the pergola on the knoll, so the area behind him would have been very close to the spot identified by so many other witnesses and by the acoustical evidence.