Amazon's audiobook division, Audible, has teamed up with dog behaviour expert Cesar Millan to produce a series of books intended to help keep your pet calm while you're away.

Dogs quickly get used to hearing human voices around the home and miss them when they leave for extended time. Millan explains how dogs can become stressed and anxious when left alone.

A free guide called Audible for Dogs includes a curated selection of books introduced by Millan, who explains in a recording why each title was chosen for a canine audience. The books include Pride and Prejudice by Jane Austen, performed by Rosamund Pike, Kenneth Grahame's The Wind in the Willows, performed by Shelly Frasier, and, perhaps unsurprisingly, A Dog's Purpose written by W. Bruce and read by William Dufris.

"Dogs are social animals, so they need to engage with someone and the purpose of Audible for Dogs is to make dogs feel there is someone with them," Millan said. "The person performing the audiobook is actually keeping your dog calm and taking the dog to a resting state, acting as an extension of you...The dog gets used to human talking, but when the human leaves, that's when he misses that tone, that's when he misses that conversation."

Millan partnered with Audible to conduct a study into what impact audiobooks have on dogs when they are left alone for extended amounts of time. Using volunteers and their dogs, the research found pets left with an audiobook playing exhibited a more positive behaviour than those left in a silent house.

In turn, this knowledge made owners feel more positive about leaving their dogs alone. Leslie, a participant in the study, said of leaving her dog Buddy alone with an audiobook playing: "I would always feel guilty about leaving [him] alone, but with the Audible book I felt like I was leaving him with a friend, so it gave me a great feeling of comfort to be able to do that and it relieves some of my guilt when I had to go out."

The new service was inspired by a 2015 academic study which found that listening to audiobooks outperformed music in reducing canine stress. Research conducted by Amazon on 100 dogs and their owners found that 76% of owners who played audiobooks reported increased calmness from their dogs over a four-week period.

As for which books work best, Millan suggests dog owners match audiobooks with their own voice, so male owners should play books narrated by men.