The phone rings. You pick it up and say "hello." There's a brief silence and then a woman's voice says, "Oh, hi there!" She offers an embarrassed laugh. "I'm sorry, I was having a little trouble with my headset!"

I've gotten this call a number of times in recent weeks, at home and at work, and each time I've been suckered by the lifelike opening to stay on the line longer than I normally would for a robocall.

This is a new and highly sophisticated racket known as the "can you hear me" scam, which involves tricking people into saying yes and using that affirmation to sign people up for stuff they didn't order.

Natural-speech technology is advancing so quickly that it may be only a few years until we won't be able to tell if we are speaking with a machine.

"This stuff is all coming together now in a way that's getting very close to artificial intelligence," said Marilyn Walker, a professor of computer science at the University of California at Santa Clara.

The "can you hear me" scam doesn't seem to be using that level of technical achievement, but it displays a sneaky savviness about how to manipulate people.

As the scam plays out, the recorded voice will raise the possibility of a vacation or cruise package, or maybe a product warranty. She will ask if you could answer a few questions. Or she will make it sound as if her headset is still giving her trouble and say, "Can you hear me?"

Don't say yes.

Police departments nationwide have warned recently that offering an affirmative response can be edited to make it seem that you have given permission for a purchase or some other transaction.

Walker said we are seeing the next iteration of speech technology in the likes of Apple's Siri and Amazon's Alexa — devices that can respond to users' requests and, to a limited extent, give the impression of conversation.

The next step, she said, will be computers that respond to voice commands to perform multiple tasks across multiple websites or platforms. For example, booking airline seats, a hotel and a rental car without a human having to look at a screen or touch a keyboard.

Walker said the more that machines become human-sounding the more they can be taught to pepper conversations with the occasional "um" or "uh-huh," or to laugh at the right moment. They will soon convey what sounds like emotion and will adjust their vocal pitch to match the context of the discussion.

She is leading a team of graduate students that is competing for the first Alexa Prize, an award offered by Amazon for the university that can come up with a "socialbot" capable of genuine chitchat.

Each of the 12 sponsored teams has received $100,000 from Amazon to fund the work. The team with the best-performing bot will win $500,000. Obviously, any technical advances will be considered for future versions of Alexa.

Art Pettigrue, an Amazon spokesman, said "we're really at a tipping point for so many elements of the technology.

"We're in a golden age of machine learning and AI," Pettigrue said. "We're still a long way from being able to do things the way humans do things, but we're solving unbelievably complex problems every day."

Think the "can you hear me" scam sounds devious? Just you wait.

David Lazarus writes for the Los Angeles Times.