As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, PILOTS HEARD AN AUDIBLE POP, FOLLOWED BY SIGNIFICA NT VENT NOISE. PER CREW VERBAL, NOISE WAS EXTREME COMING FROM OVERHEAD IN FLIGHT COMPARTMENT, COULD NOT HEAR RADIO TRANSMISSIONS. ACCOMP FIM 21-20 TASK 801 FOR LOUD AIR NOISE IN COCKPIT. REPLACED OVERBOARD EXHAUST VALVE IAW MM 21-58-05. OPS CHECKED NORMAL.