As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR DUCT OVERHEAD ROW 3 AISLE VERY LOUD WITH PACKS ON ALSO WITH EXTERNAL AIR. AT CTR DIST DUCT LOUVER PRODUCTION BREAK, AIR NOISE IS LOUDER THAN NORMAL. THE DUCT IS SECURE AND THERE IS NO STRUCTURAL ISSUE. THE METAL CLIP THAT COVERS THE PRODUCTION JOINT DOES NOT PROVIDE A COMPLETE SEAL. TAPED OVER THE PRODUCTION JOINT AS VIEWED FROM THE CABIN AS A INTERIM REPAIR. AIRFLOW IS WELL WITHIN NORMAL RANGE.