I like to listen to podcasts and screencasts at two or three times the recorded speed. The application I use (Instacast) does this with pitch correction, a feature that’s probably built into iOS at this juncture. In short, I can listen to a thirty minute podcast in ten to fifteen minutes and they only sound funny when music plays. I do mean funny; listen to Radiohead’s “Creep” at 3x speed and it comes out downright chipper.
Our brains can process speech at these accelerated rates just fine. In fact, when I listen to some of my favorite podcasters in “real” time, they sound like they’re thinking really hard and speaking slowly, or that they’re flat-out drunk. The interesting bit is when an accelerated speaker has an accent or when there is radio interference with the FM transmitter I use in the car. At this point, all bets are off and I have to slow the podcast down or listen when the signal is better.
The bottom line is that, empirically, human speech has built-in redundancy. We tend to speak at a rate that, if you miss some sounds, you can probably still make out the words. Further, the space in-between words is probably filled with our own thoughts anyway; we only listen part of the time we’re listening.
Nifty things, our brains are.