As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
L1 DOOR SQUEAL IS EXTREMELY LOUD AND UNBEARABLE FOR FLIGHT ATTENDANTS. DURING PRESSURIZATION FOR TROUBLESHOOTING, SQUEAL COMING FROM THE FWD LAV. REMOVED AND REPLACED FWD LAV SMOKE DETECTOR IAW AMM 26-14-01. SMOKE DETECTOR OPS CHECKED GOOD. REPRESSURIZED, SQUEAL GONE. OK TO CONTINUE.