Hunter 1912 mission ceiling fan 21978 hums at medium speed, and louder on high speed. No hum on low. It is a new, reconditioned from factory fan.

Hey how are you doing.

This from Ceiling Fans 'N more troubleshooting guide - why does my ceiling fan make a humming sound?

"In the case of noise complaints by fan owners, the vast majority encompass a humming noise when the fan motor is running. This is because all motors create vibration, and the humming sound you hear is that vibration being amplified by the fan housing..."