I recommend you read the WC Testimony of Lee Bowers. He directly addressed Sounds coming from the Triple Underpass vs Sounds coming from the TSBD. He disputes your premise as to a "difference in sounds of gunshots would be immediate apparent.............". Bowers not only worked for the railroad and manned that Tower for 15yrs, he also sand blasted the exterior of the TSBD. He was extremely familiar with the acoustics inside Dealey Plaza.
Sorry it doesn't work that way, first you must research the
94% of eyewitnesses who were ALL present in Dealey Plaza and who ALL agree that they heard gunshots from only ONE direction.
Get back to me after you're done.
JohnM