No audiobooks are currently available that fit into this category. There are, however, books in production.
The audiobooks for sleep are divded into two categories. First, there is Sleep Stories. These will take you through an imaginary adventure that will help you fall asleep. It will be just like listening to a story, picturing what happens in your mind until you, hopefully, fall asleep. The second category is Physical Relaxation Exercises for Sleep. This means that the only focus is making you body relax, it does not involve the use of your imagination.