It's unused voice files of conversation.

If you've played Farcry1, you know that there were many voice files of conversation in game. Those conversation of mercs change according to progress of story. It was one of pleasure to listen it. But Crysis1 lost it. Crysis1 didn't have it. We can listen the conversation only in a part of a part of the game. And only very very few patterns unlike Farcry1.

However, actually... there are many voice files of conversation in game data. Most people don't know this. Crytek made many conversation of US soldiers & others, too. Crytek prepared those voices, but they didn't use 98% of them. That was a big mistake. Those are interesting & fun.

Anyway, you should listen them if you don't know.
They are stored in Game/ (~~~.pak) /Localized/Languages/Dialog/Each Level Folder.