As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT #1408 CDG-JFK (ETOPS)."REVERBERATING (HALLOW) SOUND UNDER FLIGHT DECK AND FORWARD GALLEY AT CRUISE (ALL INDICATIONS NORMAL). NOISE DISAPPATED AFTER 1 HR.; REMOVED AND REPLACED FAN-BLOWER AVNCS VENT (20HQ) OPS CHK NORMAL PER TASK 21-269-51 AND PERFORMED TSM TASK 21-26-00-810-837A UP TO STEP #3."