I belong to Audible.com and I've developed fifteen titles with ACX.com. The process of choosing a narrator was a well-thought-out one as well as an instinctual one when I heard the right voice. It was well-thought-out in the fact that audio quality had to be superb--no background noise, no distracting mouth noises, a voice floating in a vacuum making only the words important. It was instinctual when I could listen to a voice and say, "He is my hero. She is my heroine."
I have always listened to audiobooks. I've been impressed by many narrators and put off by others. I've stopped mid-book because I just couldn't connect with the narrator. I've been propelled forward into a novel because I couldn't wait to hear the next scene. In an audiobook, it's all about enjoyment in listening. Tastes are as varied as the number of listeners. This is one reason why I used a variety of narrators when I chose them for my books, though I did like two of the male narrators so much that I used them for three books each!
Especially when I'm trying a new author, I listen to the sample first. Here is what I listen for:
Pacing--Does the narrator's pace work for me? Some narrators read so fast that I can't absorb the words. I listen for that because listening should be an easy experience, not a struggle to keep up.
Natural conversation--Can you tell the dialogue from the narration? Does conversation flow easily as if you were overhearing it at your favorite fast food restaurant? Can you tell who is speaking? Is there a change in voice for each character?
Expression--Is emotion coming through the words? Are the words more than words? Can you feel the story in your heart as well as hear it in your mind?
Style--Do you want to feel as if you're watching a play? Or would you rather have a narrator read to you?
The whole experience comes down to getting lost in a story. If a narrator can take you with him or her into the essence of a book, you will enjoy hours of storytelling and feel as if you've attended a play.