As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA FLIGHT NR 2334: ON TAXI, FA HEARD LOUD GROWL SOUND AROUND ROW 12 AND BACK. ON PARKING, TURNED OFF PTU AND SOUND WENT AWAY. MAINTENANCE FOUND PARK BRAKE ACCUMULATOR (MOUNTED UNDER PTU) CLAMPS LOOSE. TIGHTENED CLAMPS. RAN PTU, NOTICEABLE NOISE DROP IN PTU OPERATION. OPS CHECK GOOD. NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.