I just got done listening to Michael Robotham's "Lost." It's narrated by an older-sounding guy; the entire time, I could hear the spit being sluiced around in the channels between his dentures and his gums. Every once in a while, there was the artificial silence that's made when the person who's mixed the file takes out the background noise. From the noises coming from the narrator's mouth just beforehand, it sounds as if the silence gave the guy a chance to hawk up a gallon of spit.
I wonder if having dentures in your mouth is like having hard candy that never dissolves? I know that when I first have a new filling or crown, my mouth waters at the presence of an unfamiliar thing, and my tongue plays with it constantly. Did this guy, upon getting fitted with brand-new dentures, think "Now's a GREAT TIME to record an audiobook!"?
The only other explanation I can find for those noises was that he was performing oral sex while giving the reading. If that's the case, well, the lack of moaning in the background testifies that he was giving more of his concentration to the book.