As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 2 ENGINE HUMMING NOISE CHANGING IN PITCH DIRECTLY PROPORTIONAL TO VIBRATION IN THROTTLE, ALL OTHER PARAMETERS NORMAL, POWER RETARDED TO IDLE, HUMMING & VIBRATION STOPPED. REMOVED AND REPLACED NR 2 ENGINE PER JOB CARD DC8-UM-003. OPERATIONAL CHECK ON ENGINE RUN NORMAL.