As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB STRONG NOISE WAS HEARD CLOSE TO THE RT AFT WINDOW IN THE COCKPIT AND BETWEEN 15 & 16 ROW CEILING IN THE CABIN. WHEN LEVELED OFF AT FL310 THE AHRS NR 2 WAS LOST, CONTINUING THE FLIGHT WITH TRANSFER BOTH ON 1. RETURNED TO BOGOTA. CIRCUIT BREAKER B10-396 AND AHRS FAN NR 2 WERE REPLACED AHRS 1 & 2 WERE SWAPPED IN ACCORDANCE WITH AMM 34-21-10/201. TESTS OK.