Listening very hard for sounds you personally believe ought to be present on old videotapes isn't an even vaguely scientific way to eliminate any kind of hypothesis. Consider this video of the event. The TV crew's camera uses a directional mic that is focused on the woman being interviewed. It can't possibly pick up sound from many blocks away. But notice how the woman suddenly exclaims "holy shit!" and ducks slightly when building 7 starts to collapse behind her, completely out of her sight (@ 2 minutes in the video). She has clearly heard something very loud and sudden at that point. The cameraman also involuntarily reacts by ducking down as if he heard an explosion, and (less significantly to my point) there is an audible reaction from the nearby crowd as the building starts to fall. Instead of attempting to count audio events you personally imagine really ought to be present on some old tapes, you should be asking exactly what kind of forensic science was carried out in terms of analysing the physical evidence from the building to eliminate the possibility of explosives or accelerants. This is no more than is demanded by forensic fire investigation codes, and is no more than anyone with a genuine respect for the scientific method would ask for.