The answer to 'ductwork making loud noise' is that there are several common causes, including air leaks, loose connections, and obstructions in the ductwork. Symptoms may include whistling, banging, or rattling noises coming from the vents or ductwork. Some simple solutions you can try at home include sealing any air leaks with duct sealant or metal tape, securing loose connections, and checking for and clearing any blockages or debris.
However, if the noise persists or you're unsure of the cause, it's best to call in a professional HVAC technician. They can properly diagnose the issue and make any necessary repairs to your ductwork to restore quiet, efficient operation.