As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRBORNE ABOVE 12,000 FT, COCKPIT RECIRC FAN AIR NOISE WAS EXTREMELY LOUD. HARD TO HEAR COMS. VERIFIED DUCT CLEANING REQUIRED. REPLACED RECIRC FILTERS ON BOTH LT AND RT. REPLACED FCV ON LT SIDE. VERIFIED NO LEAK AND NO DAMAGE ON CTR DUCTS. DECIBAL READING IS 74 WITHOUT RT RECIR FAN AND 76 DEC WITH RT RECIRC FAN. WELL WITHIN LIMITS.