As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: EXTREMELY LOUD HIGH PITCH NOISE OUT OF FL290. HAD TO DESCEND FROM FL350 BACK TO FL 290 TO MAKE NOISE BARE-ABLE . ALL PRESSURE INDICATIONS NORMAL . NOISE SEEMS TO BE COMING FROM WINDSHIELD. **SUPPLEMENTAL REPORT WILL BE SUBMITTED** (OPEN)