SANFORD, Florida (CNN) — A forensic audio expert who analyzed 911 recordings disagrees with speculation that George Zimmerman uttered a racial slur moments before shooting Trayvon Martin to death.

What the neighborhood watch volunteer whispered as he followed the teen leading up to the deadly confrontation could weigh into the decision about charges against Zimmerman.

The garbled word that raised controversy was “punks,” not “coons,” said Tom Owen, chairman emeritus of the American Board of Recorded Evidence.

When Owen used a computer application to remove cell phone interference, the word became clearer, he said. After discussions with linguists, he became convinced that Zimmerman said “punks,” he said.

He provided CNN with a copy of the processed audio.

Zimmerman told his lawyers that he said “These f—ing punks always get away,” his lawyers told CNN on Thursday.

Martin’s family and supporters say Zimmerman, who is Hispanic, profiled Martin, who was black, as “suspicious” and ignored a police dispatcher’s request not to follow him. Martin did not live in Sanford, but he was there with his father, whose fiancee lives in Zimmerman’s neighborhood.

Zimmerman, 28, fatally shot Martin, 17, on February 26. The case has triggered a nationwide debate about Florida’s “stand your ground” law, race and racial profiling.

While Zimmerman’s lawyers may welcome Owen’s analysis of their client’s 911 call, they disagree with his conclusions about what is heard on another 911 recording.

Zimmerman has said he was yelling for help, according to his family members and his account to authorities, as first reported by the Orlando Sentinel and later confirmed by Sanford police.

But Martin’s relatives, including his cousin Ronquavis Fulton, have said they are certain the voice heard on the 911 call is Martin’s.

Owen and another audio expert, Ed Primeau, analyzed the recording for the Sentinel using different techniques, and they said they don’t believe it is Zimmerman who is heard yelling in the background of one 911 call. They compared the screams with Zimmerman’s voice, as recorded in a 911 call he made minutes earlier describing a “suspicious” black male.

“There’s a huge chance that this is not Zimmerman’s voice,” said Primeau, a longtime audio engineer who is listed as an expert in recorded evidence by the American College of Forensic Examiners International.

“After 28 years of doing this, I would put my reputation on the line and say this is not George Zimmerman screaming.”

Owen also said he does not believe the screams came from Zimmerman.

He does not have a sample of Martin’s voice for comparison, he said.

He cited software that is widely used in Europe and has become recently accepted in the United States that examines characteristics like pitch and the space between spoken words to analyze voices.

Using it, he found a 48% likelihood the voice is Zimmerman’s. At least 60% is necessary to feel confident that two samples are from the same source, he told CNN on Monday — meaning it’s unlikely it was Zimmerman who can be heard yelling.

The experts, both of whom said they have testified in cases involving audio analysis, stressed that they cannot say who was screaming.

— CNN’s Martin Savidge and Tristan Smith contributed to this report.