Not sure of the sources, but a commenter on a blog wrote some background on the “forensics expert”, Tom Owen:
“The Self-Refuting Expert Witness The Orlando Sentinel Is Touting”
...”Tom Owen. Is he really a “forensics expert?”
Well, no. He has a B.A. in History, not forensics.
...Well, but surely he’s worked for the FBI or CIA as a forensics examiner?
No, but he did work for the New York Public Library in charge of their Rogers and Hammerstein archive.
But surely he’s written some books about forensics that the FBI and CIA use, right?
No, but he has written extensively about the banjo and did a coloring book:...
But surely he’s a member of the American Board of Recorded Evidence?
Yes, but he and his wife run the Board. He’s the chairman, and she’s a board member. The Board is run out of a weight-loss clinic in Springfield, Missouri along with a bunch of other dubious “boards,” “colleges” and “Institutes.”...
Wayman fired back in a later email exchange. “There is no accepted standard regarding metrics for voice comparisons,” he insisted, “either if done forensically or using automated comparison software.” Read more: http://dailycaller.com/2012/04/06/voice-forensics-experts-cast-doubt-on-orlando-sentinel-analysis-of-trayvon-martin-911-tape/#ixzz1rNsMNDzb
From the article...
Now, let's examine the software they used to perform their analysis. How good is it?
Well, given two KNOWN samples of speech by President Richard M. Nixon, the software only matched two recordings to a 86% match.
Remember, Mr. Owen said he'd expect a 90% match before he concluded that the voices were identical.
The comments to the article are further enlightening.