As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS CRUISING AT 43K, CREW NOTED AN EXTREMELY LOUD AIR NOISE AROUND CABIN DOOR. CREW REQUESTED A LOWER ALTITUDE AND WAS GRANTED TO 35K, THROTTLES WERE RETARDED TOWARD IDLE AND A LOUD POP WAS HEARD AROUND CABIN DOOR SEAL. CABIN PRESSURIZATION COULD NOT BE MAINTAINED. CREW DECLARED AN EMERGENCY. (M)