Gabra Zackman is a new kind of acting star: She is heard, but unheard-of.
Zackman had classical training through the Shakespeare Theater of Washington, has worked in regional theaters for the last two decades and has had a sprinkling of appearances on television shows like "Law and Order." Those performances, however, have brought neither fame nor fortune.
Instead, like a growing number of actors, she has found steady employment as a reader in the booming world of audio books.
In recent years, Zackman has recorded more than 200 titles, and she says she can now count on steady work of two books a month, earning $1,000 to $3,000 a book. The income helps her make the payments on her one-bedroom Manhattan apartment while giving her the freedom to travel around the country and perform.
Once a small backwater of the publishing industry, in part because of the cumbersome nature of tapes, audio books are now flourishing. Sales have been rising by double digits annually in recent years. A recent survey by industry groups showed that audio book revenue climbed 22 percent in 2012 compared with 2011.
Much of the growth can be attributed to the business's digital transformation from how books are recorded (increasingly at studios in the actors' homes) to how they are sold (through subscription or individually on the Internet) and consumed (downloaded to mobile devices).
That development is good for publishers and authors, of course. But it has also created a burgeoning opportunity for actors pursuing stardom on the stage and screen, allowing them to pay their bills doing something other than waiting on tables.
Zackman says the demand for her work is tied in part to her dedication to her craft, and she does extensive research before each book, with the aim of infusing intonation and emotion into each character's voice.
She also gives credit to Audible.com, a company in Newark, N.J., that is pushing the digital revolution in audio books, and which has become her main employer.
Audible, the biggest producer and seller of audio books, says it produced about 10,000 recorded works last year either directly or through a service it provides that allows authors to contract directly with actors. Each book amounts to an average of two or three days in the studio, but can be more, for the person voicing the book.
Donald Katz, the founder and chief executive of Audible, which was bought by Amazon.com in 2008, said that his company employed 2,000 actors to read books last year, and he speculated that he was probably the largest single employer of actors in the New York area.
As with other forms of acting, compensation varies according to fame. An unknown actor might earn a few thousand dollars for a book, while stars like Nicole Kidman, who recently narrated Virginia Woolf's "To the Lighthouse" for Audible, can be paid in the hundreds of thousands.
The field is so promising that drama schools, including Juilliard and Yale, have started offering audio narration workshops.
Katherine Kellgren has led narration classes at various acting schools. She said she was excited that audio narration, which is different from other forms of acting, is finally getting recognition as a craft.
Kellgren attended the London Academy of Music and Dramatic Art for three years, where she says she trained intensely in dialects. She did radio plays early in her career, which helped prepare her for audio work.
For her first book, she auditioned for the producer over the phone by reading selections from "Out of Africa." She got the job, which was for a bodice ripper called "Wicked Widow," just the mention of which still makes her giggle with embarrassment.
Now, Kellgren, who refers to herself as an audio book narrator instead of an actress, can command as much as $450 for each finished hour of narration and can be picky about the work. "When books get too spicy for me, I turn them down now because I dissolve into hysterics," she says.