The ductwork in your home may make loud noises for a number of reasons. One possibility is that the ducts are old and need to be replaced. Another possibility is that there is something blocking the airflow through the ducts, such as a build-up of dust or dirt. A third possibility is that there is something wrong with the fan or blower that is causing it to overwork and create excess noise. If you think there may be something wrong with your ductwork, it is best to have a professional inspect it and diagnose the problem.