13 second collapse.

Its often debated how long the actual fall of 3 buildings took by looking at the video, it can get confusing. I was looking at this old video:

The collapse on the audio is clearly 13 seconds, from 3:04 to 3:17. It is delayed due to the distance, but plain as day. Someone else had made a remix of this video to "enhance" (in other words ruin any chance of being taken seriously) the audio. I thought having an unbiased sample would be nice.