Ductwork Makes Banging Noise: Causes & Solutions

homeowner covering ears due to noisy hvac ductwork

Central heating and air conditioning systems produce warm or cold air in a central location and distribute it throughout the house through ductwork. Metal ducts, which are commonly used, are prone to making noise when disturbed. This can be very annoying and can disrupt sleep for homeowners if the noise becomes loud and frequent. Learn more about the causes and ways to reduce ductwork noise here.

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Possible Reasons Behind Ductwork Noise

Noise from HVAC ducts can have various causes. Pay attention to the sounds to determine the type of noise. You can gain insight into the problem by listening to the noises, even if you cannot physically see them. A common issue is a banging sound from the HVAC ductwork.

Ductwork Is Banging

Many homeowners experience banging or popping noises coming from inside their ducts. These noises usually occur in short bursts. This is caused by the duct walls expanding and contracting with temperature changes, as well as pressure fluctuations. Hot air leads to duct expansion, while cold air causes contraction. You can’t see this happening, but you can hear it a few minutes after turning on the air conditioner or furnace.

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Causes For Other Ductwork Noises

Ductwork can produce various noises other than banging and popping. Some noises and their causes include:

Rattling Ductwork

hvac ductwork

The rattling sound inside your air ducts is likely caused by loose metal parts knocking against each other. This can occur as ductwork ages, seals fail, and connections become loose from static pressure. The noise will persist as long as air circulates and may start softly but intensify until it becomes impossible to ignore. To solve the issue, seek assistance from HVAC professionals.

Booming HVAC Ductwork

The loud booming sound could be coming from the junction between the trunk and plenum of the duct, which experiences the largest temperature change. If this connection lacks the proper expansion joints or dampers, the sound will travel throughout the house through the supply ducts. Experienced installers are aware of this potential issue and can take steps to minimize the noise from the connection.

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Shaking HVAC Ductwork

You may sometimes observe the ducts shaking or vibrating with a low hum. This often happens when the return side’s airflow is obstructed by a dirty air filter. The low pressure caused by the blocked air can lead to the ducts shaking and vibrating. Regularly checking the air filters is a good practice to prevent this issue. If the filter is too dirty, clean or replace it for a quieter duct operation and better system efficiency.

Scratching Noise From Ductwork

image of a rat in hvac ductworkAn unpleasant sound coming from the air ducts may indicate the presence of rodents, raccoons, squirrels, or other critters that have gained entry into the system. If you hear a scratching noise on the metal walls, it is crucial to act quickly to prevent them from building a nest and impacting air quality. If you hear a buzzing sound, it could be from a bee or other large insect that’s trapped. Contact an HVAC contractor for immediate assistance.

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How to Reduce The Noise From HVAC Ductwork

Homeowners can remove the noise from their ductwork by removing creatures and foreign objects. Competent HVAC technicians can also repair problem areas. The normal operation-related noise can also be reduced and made bearable for a quiet home by employing the following solutions:

Adjust The Fan Speed

At the start, installers can adjust the airflow volume to its optimal range, taking into account various factors. However, they often set the fan speed too high. To reduce the noise, you can lower the fan speed and decrease the static pressure with the help of an HVAC technician. Keep in mind that setting the fan speed too low can result in poor air distribution in some rooms.

Change the Air Filters

image of an hvac air filter replacement

Monitor your air filters. These parts capture debris while allowing air to flow. Over time, the filters accumulate more dirt, hindering airflow. To maintain efficiency and proper airflow, it is recommended to replace filters every 2 to 3 months. In homes with multiple pets or dusty locations, you may need to replace your filters monthly. The frequency of replacing your air filters varies depending on the specific conditions of your home. Keeping filters clean can prevent banging and popping noises in the ducts. Air filters are inexpensive, so replace them as necessary for optimal HVAC performance.

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Install a Bypass Duct

To reduce pressure in a multi-zone system, consider using a bypass duct. Lowering pressure can alleviate stress on the ductwork and prevent problems. However, this solution may not be suitable for all cases. It is advisable to consult with HVAC professionals to determine if this approach is appropriate for your duct system.

Install Larger Ducts

ductwork hvac installation

Examine the possibility that your ducts may be insufficient to accommodate the necessary air volume for optimal performance. Even if your heating and cooling units are the correct size, undersized ducts can cause issues. Consult with your HVAC contractor for a proper evaluation. Larger ducts can reduce noise, as can a larger return and supply plenum, along with high-velocity grills and registers that enhance airflow.

Try a Different Duct Shape

Consider the shape when installing new ducts. Rectangular ducts are popular for their sleek appearance but can be noisy due to their lower pressure tolerance. Round ducts may be better if they fit in your space. Consult a local HVAC company for more information.

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Use a Duct Silencer

A duct muffler can be added to round ducts to decrease noise output. These mufflers have a dual-wall structure with integrated insulation to dampen vibrations. For optimal results, they should be placed near noisy components like the air handling unit, fan, etc. Keep in mind that mufflers can reduce noise, but they cannot completely eliminate it.

Insulate the Ducts

Wrapping insulation around the ducts can enhance energy efficiency and reduce noise, particularly banging and popping sounds. For optimal results, have a certified technician complete this task.

Switch to a Ductless System

If you have tried the above noise reduction methods but are still dissatisfied, consider switching to a ductless mini-split system to completely eliminate ductwork noise and maintenance. This option offers benefits such as creating multiple temperature zones, independent temperature control, and improved energy efficiency.


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Ductwork noise can indicate various issues, such as loose connections, pest infestations, incorrect system configurations, and other problems. This noise serves as an alarm for homeowners to address these issues. However, even regular system operation can result in noise. While you can implement different strategies to reduce the frequency and volume of noise, it may not disappear completely. Consult a trustworthy HVAC technician for the most effective solutions for your system.

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