The answer to 'why is my dehumidifier making loud noise' is that a dehumidifier can make loud noises for several common reasons. This could be due to a malfunctioning fan, a loose component, or a problem with the compressor. The loud noise may also be caused by the dehumidifier working harder than normal to remove excess moisture from the air.
If your dehumidifier is making loud noises, first check the air filters and clean them if needed. Ensure the dehumidifier is level and sitting on a stable surface. You can also try tightening any loose screws or components. However, if the noise persists or you're unable to identify the cause, it's best to call in a professional HVAC technician to diagnose and repair the issue.