Audiobooks played in a recent study conducted by researchers at Hartpury College in the United Kingdom resulted in dogs spending more time resting and less time displaying vigilant behaviors. This is a new dimension beyond the considerable studies on how music effects dogs.
Source: The Bark, February 11, 2017.
The book used in the experiment was The Lion, The Witch and The Wardrobe performed by Michael York. Given the calming effect of the audiobook, it would be interesting to do a follow-up study comparing the effect of different audiobooks and voices, as well as other speaking tracks, like the news.