I suggest you watch this documentary below, the Google Video link will take you to the part 2 of 3. video.google.com...
The documentary is called 9/11 Eyewitness and it explains in great details how the rumble sounds were heard not only during the tower's implosion but
BEFORE the onset of the collapse as well. That part 2 of 3 will show you somewhere in there how the noises were heard and how loud and pretty detailed
too.
You can watch the whole documentary here: video.google.com...
Strangely enough, some extremely loud demolition sounds were heard just before the WTC7 collapse as well. See the following YouTube link for
details: www.youtube.com...
I can't possibly see how the Conspiracy sketptics are going to refute it. I have seen no attempt on their behalf to do so. I can only surmise that
they know just as well as we do. But just can't admit it to themselves.