As Arthur Moses first revealed in 2012, the Houdini voice recording that is publicly available is actually an edited combination of two different recordings Houdini made introducing his Water Torture Cell in 1914. For those who have the recording burned into your brains, have a listen starting around 4:08 and you'll hear the differences.
For those who don't know the recordings as well, highlighted below are the differences:
"Ladies and gentlemen, I take great pleasure in introducing my latest invention: The Water Torture Cell. Although there is nothing supernatural about it, I claim that it is absolutely impossible..."
I should point out that Tom Interval used the first sentence in his excellent clean-up and restoration of the original recording (which can be heard here), so that may sound familiar. But the last line -- "I claim that it is absolutely impossible" -- has largely gone unheard.
I've had the pleasure of hearing both the full recordings on a few occasions. Click on over to Arthur Moses official website to read transcripts of those two unedited recordings.