Cockpit voice recorders record the dialogue between pilots and air traffic controllers and that between pilots. In addition to flight-related dialogue, a great portion of such dialogue concerns pilots' personal privacy, and is completely unrelated to flight operation. In the process of aviation occurrence investigation, ASC only transcribes verbatim of the voice data related to flight operations to protect the pilots' rights to privacy. Both ICAO regulations and national Aviation Occurrence Investigation Act expressly stipulate that the recordings of cockpit voice recorders must not be disclosed.