The answer to 'ductwork making loud noise' is that there are several common causes, including loose or damaged ductwork, obstructions in the system, and problems with the blower fan. Symptoms may include rattling, whistling, or banging sounds coming from the vents or ductwork.
Some potential solutions include tightening or sealing loose ducts, removing any blockages, and checking the blower fan for issues. However, if the noises persist or you're unsure of the cause, it's best to call in a professional HVAC technician to diagnose and repair the problem. They have the expertise and tools to properly inspect the system and make any necessary repairs.