Identifying Strange Duct Noises

duct noiseMost air duct noises don’t mean serious trouble, but they’re still not something you should ignore. By paying attention to your ducts, you’ll help your air conditioner keep you comfortable efficiently even in the long, warm summers of the Greater Los Angeles area.

Intermittent pops and bangs – Usually, these duct noises happen when the sheet metal ducts expand and contract due to the warm or cool air blowing through. It’s especially common after duct cleaning. Removal of built up dust and debris allows the ducts to move in ways they couldn’t before. A loud bang where the trunk duct connects to the plenum is also common because this is the area most affected by temperature changes.

The noise is harmless, but if you find it annoying, there are solutions, such as acoustic duct liners. Loud, repeated bangs, on the other hand, suggest a loose metal object in the duct, such as a damaged zoning damper.

Whistling – This is a sign of restricted airflow. If it started suddenly, it suggests a blockage in your ducts caused by a foreign object or collapsed flex duct. If your ducts have always whistled, there’s a good chance they’re undersized and not allowing for sufficient airflow. This places damaging strain on your HVAC system’s components, so it’s worth contacting an expert about having your ducts assessed.

Vibrating or shaking – Like whistling, these duct noises usually mean restricted airflow. Vibrations can eventually damage your system. If the problem has just started, make sure your air filter isn’t clogged. Sometimes ducts vibrate simply because they were poorly installed. In this case, you can screw the duct to the wall or consult an expert for help.

Rattling – If something’s rattling around in your ducts, chances are it’s a foreign object that’s fallen in. It might be a loose screw from somewhere in the HVAC system or a pen, child’s toy or other item that fell into the air vent. In older duct systems, the rattling may be coming from connections or sealing materials that have worked loose over time.