Identifying And Resolving Problems With Excess Noise In Your HVAC Air Ducts

image of a homeowner covering ears due to hvac ductwork making noise

Central HVAC systems produce hot and cold air in one location and then use ductwork to move it throughout the home. HVAC ducts are typically comprised of metal, and this means that they’re prone to making noise when disturbed. This ductwork noise can become annoying to homeowners if it grows loud or when it’s present all of the time. It can make it all but impossible to get a good night’s sleep. Continue reading to find out why ductwork noise occurs and to discover a few effective strategies for reducing or preventing it.

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Several Possible Reasons for Ductwork Noise

There are several possible reasons why ductwork might produce noise. Try listening carefully to ductwork noise to better understand the exact type of sounds that are being emitted. Although you may not be able to see the source of the issue, you can still seek it out by paying attention to what you hear. Loud banging noises are among the most common types of HVAC ductwork noise.

Banging Noise Coming From HVAC Ductwork

Homeowners often report noise that’s akin to having something banging, clanging, or popping around in their ducts. These noises tend to come in quick bursts. They’re caused by the natural expansion and contraction of duct walls as the temperature inside of HVAC ducting rises or falls. This type of noise can also be the result of sudden changes in pressure. Keep in mind that warm air will make duct walls expand and cooler air will cause them to contract. Even though these movements might be imperceptible to the naked eye, homeowners can certainly hear them happening right after their air conditioners or furnaces kick into action.

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Other Causes for Noise in HVAC Ductwork

Banging, clanging, and popping sounds are hardly the only type of ductwork noise that you might hear. Following are a few common sounds along with the reasons why they occur.

Rattling Ductwork Sounds

hvac air ductsRattling noises coming from inside of your HVAC ducts is a likely indication that there are loose parts. Metal parts make audible sounds when they get knocked against one another. This is most common with older components. Static pressure can cause their connections to loosen and their seals to fail. You’ll hear rattling sounds whenever air is actively moving through your HVAC air ducts. Although the noise might be soft at its start, it will gradually get louder until it can no longer be ignored. You can find this problem and fix it with the help of a qualified HVAC technician.

HVAC Ductwork Is Making Booming Sounds

This is a loud noise that you’ll likely hear coming from the junction of the plenum and the duct trunk. This is where the biggest fluctuations in temperature occur. When there aren’t enough dampers or expansion joints at the connection, this booming noise will reverberate throughout your entire home via the supply ducts. Seasoned HVAC technicians know why this happens and thus, they take steps to limit and ultimately prevent noise at this connection.

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Shaking HVAC Ductwork

At times, you may hear the low hum of HVAC air ducts that are vibrating or shaking. This is usually due to a blockage on the return side that’s causing airflow issues such as a dirty HVAC air filter. Given that air is unable to enter the system, the air pressure within the ducting falls so low that the duct walls start vibrating and shaking. Regular check your air filter. If it has accumulated a fair amount of debris, clean it up or change it out. You’ll have less noise in your ducting and your heating and cooling equipment will function more efficiently.

Scratching Sounds in HVAC Air Ducts

image of a rat in hvac ductwork

Scratching is another unpleasant sound that you might hear in your HVAC air ducts. It may seem like something is scratching at the walls of your ducts and this sound is a strong sign that there are raccoon, squirrels, rats, or other pests that have entered the system. Take action to correct the problem right away before pests start building nests and settling in where they’ll diminish your indoor air quality (IAQ). If you hear any buzzing noises, this could be the wings of an insect such as a bee that’s gotten trapped inside. Call an HVAC company to get help.

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How to Limit Noise in Your HVAC Air Ducts

HVAC ductwork noise isn’t something that you have to resign yourself to living with for all time. You can remove both foreign objects and pests when they’re the culprit. You can have licensed HVAC technicians resolve problem areas. When it comes to sounds that are the result of basic HVAC operations, you can limit this noise and make it more tolerable for those who want peace and quiet. Following are a few practical strategies that you can use:

Change Your HVAC Air Filter

Person replacing the HVAC air filter

Regularly check and change out your HVAC air filters. These components are designed to catch and retain dirt while allowing air to pass. The more debris that they collect, the hard it becomes for air to move through them. Air filters should be replaced about once every two to three months to ensure system efficiency and optimum airflow. However, in homes with pets or homes that are in inherently dusty areas, HVAC air filters may need to be changed once each month. How frequently filter changes need to be performed depends upon the nature of your living environment. Having clean filters is one easy way to prevent noise in your HVAC air ducts. Air filters aren’t very costly, so invest in a few right now to keep your HVAC system performing as it should.

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Adjust the Speed of the Fan

The volume of HVAC airflow is configured by installers at the very beginning. There is an ideal range for every system according to various factors. In many cases, the speed of the fan is set too high. If this is an issue in your home, try lowering the fan speed to reduce the amount of static pressure in your HVAC air ducts. You might want to get help from a licensed HVAC technician with this task because dropping the fan speed too much can make it difficult for the system to deliver air to all rooms.

Have Larger Ducts Installed

hvac ductwork repair

It may be that your HVAC air ducts are too small to stay on top of the volume of air that’s necessary. Even though your air conditioner and heater might be the right size, you can still have problems if your ducts are too small. Talk about this issue with your HVAC contractor so that the matter can be investigated. Having larger air ducts
and a larger supply and return plenum put in may help with noise reduction. You can improve overall airflow a bit more by pairing these upgrades with high-velocity registers and grilles.

Have a Bypass Duct Added

When multi-zone systems have too much pressure, bypass ducts are used to mitigate it. Reducing air pressure limits the amount of stress on HVAC ducting and prevents a host of wear-related issues. However, this strategy only works in specific cases. Talk with an HVAC company to see if this noise-reduction technique will work in your ducts.

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Consider Different Duct Shapes

If you’re having new HVAC air ducts installed, think about getting a different shape. Rectangular ducts have clean lines and a slim profile, so they tend to be popular. However, rectangular air ducts produce more noise than round ones because they have a lesser tolerance to air pressure. If you can fit round ducts in your home, they are probably worth considering. Speak with an HVAC company in your area to find out more.

Have a Duct Silencer Put In

Duct noise can be muted or minimized by installing a duct muffler in round ducts. These mufflers have double-wall designs and they’ve also got built-in insulation for dampening vibration. They work best when they’re positioned next to the fan, air handling unit, or other noisome components. Keep in mind, however, that they are only for reducing unwanted sounds. They don’t eliminate them entirely.


Install Duct Insulation

You can have insulation wrapped around your HVAC air ducts to make them more efficient. This will also dampen unwanted noise, especially loud popping and banging sounds. For optimum results, have a licensed HVAC technician install your duct insulation.

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Choose a Ductless Mini-Split

If you’ve already used all of the above-mentioned strategies for reducing noise and are still unhappy, you might want to try moving away from HVAC ducting. Switching to a ductless mini-split system will eliminate duct noise and duct maintenance. There are additional perks of ductless heat pumps, including being able to create multiple heating and cooling zones, greater efficiency, and independent temperature control.



There are many possible causes for ductwork noise. At times, this is an indication of an underlying issue such as improper configuration, loose components or connections, or pests. In these instances, unwanted noise brings developing issues to homeowners’ attention. However, noise may simply be a regular part of HVAC system operations. It might not ever go away, but there are several strategies that can be used to reduce its frequency and volume. Speak with an HVAC company to find out which noise reduction strategies might work best in your home.

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