DIAGNOSIS That's a failing fuser drive gear. The plastic gears inside the right-side fuser assembly wear down or crack. The noise is the motor struggling to turn them.
FIX You need to replace the fuser. Part number is RM2-4458 (HP 46A Fuser Kit). Order the kit. To replace it, power off and unplug the printer. Open the front door and the rear output door. Pull the two blue fuser release levers outward. Slide the fuser straight out. Slide the new one in. Push the levers back in. Close the doors.
IF THAT DIDN'T WORK If the new fuser makes the same noise immediately, the main motor or gear train that drives the fuser is damaged. That requires a technician. First, double-check that the fuser is fully seated and the levers are locked.
HEADS UP The fuser is extremely hot during and after operation. Let the printer sit powered off for at least 30 minutes before you touch it. Do not use generic fusers with poor gear quality. They fail fast.