The audio from the Trayvon Martin 911 call is a tough listen.  You can clearly hear screaming in the background throughout the entire call.

There is a debate as to who's screams they actually were, and we are a little closer to an answer.

A voice expert said the screams heard on a 911 call moments before Trayvon Martin was killed were not those of George Zimmerman.

Zimmerman claims he shot the Florida teen in self-defense after he was attacked and told cops he was the one who could be heard crying out in the recording.

But a leading voice identification expert said he is certain the screams do not belong to Zimmerman. He used specialized software to compare the voice on the 911 call to Zimmerman's voice.

A different expert using different techniques came to same conclusion: The voice heard on the calls also isn't Zimmerman's.