Does a black box include the CVR (cockpit voice recorder) and FDR (flight data recorder) together? - Quora
Somehow, I don't know how, but somehow the FBI responded to my FOIA request for CVR audio from United 93, and on appeal located documents and audio responsive to my request. :
United Airlines Flight 93 - Wikipedia
Why were the passengers of Flight 93 unable to gain control of the cockpit? Was it just not enough time? - Quora
Flight 93 Cockpit Voice Recorder - Flight 93 National Memorial (U.S. National Park Service)
Flight 93 Cockpit Voice Recorder - Flight 93 National Memorial (U.S. National Park Service)
BBC NEWS | In Depth
New 9/11 Tapes: Audio And Full Transcripts | World News | Sky News