There are several reasons why a furnace can start making loud noises, and they all come from some level of furnace malfunction, as a healthy furnace is a quiet one.
Indicate a problem with the furnace’s ignition system and should be checked out by a professional
Banging, Popping or Rattling Noise
This can mean there is a problem with the blower assembly, the motor or the furnace of the furnace.
If you hear rattling noises, something is likely loose and needs attention by a professional. If you hear sudden loud banging, it’s likely that a part has broken and become disconnected, and immediate professional services are required.