As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOUD SQUEAL WAS AUDIBLE THROUGHOUT CABIN AND COCKPIT SEEMED TO BE IN FORWARD GALLEY. FOUND GALLEY DRAIN PLUGGED POSSIBLE CAUSE OF SQUEAL. CLEANED DRAIN, CLEANED GALLEY PASSENGER DOOR SEALS, PRESSURIZED CABIN TO 7.5 PSI, LEAK DOORS AND SEALS NO AUDIBLE SQEALS IN CABIN.