"The companies are competing to create the best-sounding and functioning systems. Their concern is driving revenues," said Marcus Graham, CEO of GM Voices. "Talking about the voice talent, from their perspective, is likely seen as a distraction."
Bennett's attorney, Steve Sidman, can't breach attorney-client privilege to share documents and contracts, but since he began representing Bennett in 2012 he's been intensely aware of her connection to Siri.
"I've engaged in substantial negotiations -- multiple, months-long negotiations -- with parties along the economic food chain, so to speak, that involved her rendering services as the voice of Siri," he told CNN. "It's as simple as that."
And then there's Graham, of GM Voices, a man who has built a career around providing voiceover talent for interactive voice technologies.
Graham won't divulge details about any deals he made back in 2005. But he has worked with Bennett for 25 years, has recorded "literally millions of words with Susan" and has installed her voice with clients across the globe. He knows her voice as well as anyone, and he doesn't hesitate when asked if she and Siri are the same.
"Most female voices are kind of thin, but she's got a rich, full voice," he said. "Yes, she's the voice of Siri. ... She's definitely the voice."
A '100% match'
In October 2005, a few months after Bennett made those recordings, ScanSoft bought and took on the name of Nuance Communications. Nuance is the company widely accepted to have provided to Apple the technology behind Siri.
When CNN contacted Nuance to try and confirm Bennett's identity as a voice of Siri, a Nuance spokeswoman said, "As a company, we don't comment on Apple."
Apple, too, declined to comment.
So CNN took the investigation one step further by hiring an audio forensics expert to compare Bennett's voice with Siri's.
Ed Primeau, of Rochester Hills, Michigan, has been doing this work for three decades. He's testified in courts, analyzed "hundreds, if not thousands" of recordings and is a member of the American Board of Recorded Evidence. He spent four hours studying our "known voice" -- in this case Siri -- with the unknown voice of Bennett.
"I believe, and I've lived this for 30 years, no two voices are the same," he said, after finishing his analysis of the Siri voice and Bennett's. "They are identical -- a 100% match."
To reach his conclusion Primeau created back-to-back comparison files, lifted and listened to consonants and reviewed deliveries. He took the hiss off the Siri sound, created in recording from a phone, and dropped it into Bennett's file.
After studying Bennett's normal speaking voice, he was about 70% certain of the match. But once he had audio of her saying the same words as Siri, he knew his work was done. Even so, he said he asked a colleague for a second opinion.
"I understand the importance of accuracy," Primeau said. "Rest assured: It's 100% Susan."
How CNN got this story
This isn't the sort of story I'd naturally go after. Technology is far from my beat. In fact, the first time I ever spoke to Siri was on my work phone -- the kind that's plugged into a wall jack and has a tangled cord attached to the handset.
Bennett was a voiceover artist I was interviewing for a CNN special project on the world's busiest airport -- Hartsfield-Jackson Atlanta International -- scheduled to come out next month. I was tracking down the airport's voices, and she, a voice of Delta terminals, was one of them.
In the course of our phone conversation, I asked her to rattle off some jobs she's had over the years. She gave me a quick and general rundown and then added that she's done a lot of IVR work.
"IVR?" I asked.
"Interactive voice response," she answered. "The sort of thing you hear on a company's phone system."
For reasons I can't explain -- I was still struggling to understand my first iPhone -- I blurted out, "Hey, are you Siri?"
She gasped. And then I gasped.
"Oh my God," I said. "You're totally Siri, aren't you?"