I'n not sure that this has been posted yet. It is from Today's Wall Street Journal and appears to infer that people who have heard the CVR report:
"Instead, these people said, it came from a third pilot in the cockpit, first officer Bong Dong-won, the most junior pilot on the flight who was sitting on a jump seat. Mr. Bong repeatedly yelled out the phrase "sink rate," intended to warn the two captains at the controls that the jet was losing altitude too quickly, these people said. An NTSB spokeswoman declined to comment."
Pilots' Recollections Differ From Cockpit Recordings in Asiana Crash - WSJ.com