As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEARD A BUZZING NOISE IN FLIGHT WITH AN ELECTRICAL SMELL. NO MESSAGES OR ANYTHING, NO INDICATIONS. CREW SUSPECTS IT IS COMING FROM PACK 1, NOISE AND SMELL WENT AWAY WHEN THEY TURNED IT OFF ON THE GROUND. R & R THE 1 PACK AIR CYCLE MACHINE IAW AMM 21-51-05. OPS CHECK GOOD.