Can I listen to audio at faster or slower speeds?

Yes, the listening speed can be adjusted!  

When you are listening to a passage, click the slider button at the bottom of your screen.

From there, you'll see an option for "Playback Speed". You can change the speed anywhere from 0.75x - 2x.

You are able to do this in real time, as the passage is playing, so you can understand how the changes you made impact the auditory experience on the fly.