Duct Noises Can Be Common, But What Do They Mean?


air duct noises

Good duct design is necessary to maximize home comfort and heating and cooling efficiency, yet the ductwork system often goes unnoticed and unattended. If duct noises have gotten your attention recently, keep reading to help determine the cause of the noise and what action if any should be taken.

Rattling and Clamoring

Most duct systems, especially older ones, are fabricated of thin sections of sheet metal. If the connections between duct sections are loose or disjointed, they can rattle and clamor as the sheets knock together. A skilled homeowner or a trusted HVAC pro can wrap metal-backed tape around loose joints, or add aerosol sealant or mastic paste for a more airtight seal.

Popping and Banging

Air ducts are sometimes installed outside the insulation barrier in attics and crawl spaces, which exposes them to extreme temperatures during the height of summer and winter. When heated or cooled airflow passes through ducts in these conditions, the metal walls can expand and contract. This movement causes popping and banging. Inspect all accessible air ducts and make sure the ducts are insulated. You may also install acoustic dampers if the noise is too disturbing.

Booms and Thuds

The duct trunk connects to the air handler or blower compartment at the plenum by a flexible dampening joint. If the plenum and trunk are too close, they can knock together and cause a loud boom noise. In this instance, your HVAC technician would need to reposition the parts.


Sometimes the only noise you hear from the ducts is a constant whooshing caused by airflow through ductwork components. Overly noisy airflow generally means the ducts are too small for the HVAC system. Your HVAC technician may slow the blower speed to decrease the volume of airflow. However, this option may not be practical if there’s too great a loss of comfort.

Modifications may be made to duct size, which may increase the efficiency of your furnace and A/C, and remedy the noise problem. With this in mind, remember that when upgrading HVAC equipment, make sure the contractor you hire correctly sizes the necessary ductwork.

For more tips about remedying duct noises and other A/C maintenance issues in your Las Vegas home, contact Ambient Edge.

Image via Flickr by dulasfloyd

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