She’s the voice.

You’ve heard her announce your stops on MARTA . She’s guided you across town on your car’s GPS and helped you navigate the world of a cable provider. She’s persuaded you to buy dinner rolls and, perhaps soon, she’ll come to a home appliance near you.

You may not know Liz Raphael Helgesen by name, but you’ve certainly heard her.

“The approaching station is Airport. Exit here for Hartsfield-Jackson Atlanta International Airport.”

Helgesen is among a number of metro Atlantans who do voice-over work for various companies. Hers is a voice heard around the world.

And, as smart technology continues to develop, demand is only expected to grow and become more competitive.

CNN recently reported that an Atlanta woman, Susan Bennett, is Siri, the voice-activated virtual assistant introduced in 2011 on the iPhone 4S, something Apple has never confirmed.

“Technology innovations have just exploded and continue to change the way we live,” said a soft-spoken Helgesen, the owner of Passion Fruit Voiceovers. “The customer self-service platforms that many companies use these days is where I come in, to handle service issues and create good experiences for callers 24/7.”

To put it simply, technology talks. And it pays.

David Zema, a voice-over talent, producer and coach in New York, said “businesses need better presentation than they did, say, 10 years ago.”

The Internet and smartphones have helped fuel the demand.

“We don’t see it diminishing,” he said.

Helgesen gets calls from friends who have heard her voice. Sometimes, her husband, Bob Helgesen, vice president of quality assurance for John Wieland Homes, will place a business call, be put on hold or told to go through a series of prompts, and then he hears his wife’s voice on the other end.

Her voice travels far and sometimes surprises her.

Not long ago, Helgesen, her husband and one of their four children went to the movies. In the middle of the film a character’s security system is activated, and suddenly Helgesen’s voice fills the theater, catching her momentarily off guard.

“I grabbed my husband’s and my daughter’s arms, on either side of me,” she said, “and in whispered shock, I said, ‘Oh my gosh, that’s me!’ “

Albert de Groot, a speech science manager for Massachusetts-based Nuance Communications, can’t discuss projects Helgesen has worked on for his company, citing confidentiality. But he said in an email that he rates “Liz very highly, she is one of the best around.”

Helgesen estimates that her client roster has grown by 50 percent in the past decade, mostly by word of mouth.

She recently read a Spanish-language script — with a translator in the studio for assistance — for GPS systems in South America. “They wanted me to sound like an American speaking Spanish to help guide Americans traveling to South America and renting a car,” she said. She’s also worked with transit systems in Indianapolis and Dallas and a drugstore chain.

She’s also the voice behind online readings that are designed to instill deeper reflection, inspiration and a sense of self-awareness.

Often, her name never surfaces on a project.

“I think it’s because my voice is their product or service, they own it,” Helgesen said. “Marketing departments want to maintain control of how that product or service is perceived in the marketplace. … Often, the voice is private, part of the inner workings of a product, just like a secret recipe.”

When recording, it’s not just the vocals that are at play. Helgesen, who formerly worked as a human resources manager for a telecommunications company, emphasizes the importance of connecting with the target audience and making what’s on paper “come to life.”

“I worked in the telecom industry when pressing ‘one’ and pressing ‘two’ was just becoming socially acceptable,” Helgesen said.

Her worst enemy can be a sore throat, particularly if she is updating an existing project and has to sound the same as the original recording.

Lozenges and an herbal throat spray are always within arm’s reach as she works, primarily from a sound-proof studio in the basement of her east Cobb home. She gargles a lot with salt water, and she drinks plenty of water to keep her vocal cords hydrated.

The most important tool, though, is voice rest.

“You won’t find me screaming at a ballgame,” she said. “But I will be dying inside because I want to be.”