As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
VERY VERY LOUD SQUEAL IN OVERHEAD MID COACH CABIN. PLACED CEILING LIGHT AT ROW 30-31L ON MEL. BALLAST CONNECTOR D11218 DISCONNECTED & STOWED. BALLAST WAS THE CAUSE OF LOUD HUMMING NOISE, WILL REQUIRE BALLAST PCN 563-0055 & 05814-16 BALLAST.