How To Quiet Noisy Ducts

How To Quiet Noisy Ducts

Picture this. It’s a quiet afternoon, and you’ve got the house all to yourself for a few hours. You decide to slump down into the couch and revel in a movie that’s been on your bucket list for weeks. Beaming with excitement and some snacks in one hand, you hit the play button, but just as you’re about to enjoy what would be the perfect afternoon, the air conditioner in your living room roars to life.

Let’s explore a few pointers on how to quiet noisy ducts that compromise the peace of your home or workspace. To begin, determine the cause of the noise and then follow through with some troubleshooting to eliminate the noise.

Before you consider shelling out hundreds of bucks on a new air conditioning system, here are a few foolproof ways on how to quiet noisy ducts.

What If It’s Not Your Air Duct Causing The Rattling?

Ducts don’t make much noise on their own. Instead, it’s the air flowing through them that generates the noise. Furthermore, a wealth of factors can make air movement less or more audible.

Before we delve into the nuts and bolts of noise levels and ductwork, we’ll first consider a few fundamentals of noise reduction. If the airflow through your system generates immense noise, here are the first things to check on.

Closed Vent Dampers

Although one closed damper won’t make much of a difference, closing a number of them simultaneously might generate a rattle from your system. Closing supply vents puts undue stress on your HVAC equipment. It would be a great idea to leave them open without noise.

Bent or Sagging Flex Ducts

If flexible ductwork isn’t installed properly, there’s a likelihood of it bending or sagging. Those bends and sags make it an uphill battle for your system to move air, increasing static pressure and creating noise.

Dirty Ducts or Air Filters

In the long run, dirt and dust can build up inside the ducts and air filters, making it challenging for your system to circulate air freely. Additionally, it makes the system noisier. Therefore, the solution is to replace or clean your filter frequently and have your ducts cleaned once they start impeding airflow.

High Static Pressure

It’s worth noting that the intensity of static pressure varies from one system to another. When it’s excessive, the ducts can hardly accommodate the air volume your system is trying to flow through them. When the volume of air surpasses what your ducts can handle, noise is generated. High static pressure is a common issue whose intensity varies from one home to another, calling for a unique fix.

Tips On How To Quiet Noisy Ducts

If you’ve checked all the above boxes and addressed the issues, your ducts should be quieter. However, if your attempts have proved futile, here are a few additional steps to take.

Alter the Fan Speed

Your furnace fan or blower should be set to deliver the ideal airflow per ton. Theoretically, your HVAC installer configured it properly during installation. However, in reality, not all installations are done perfectly as a boatload of fans is set at an overly high speed.

Typically, you have free rein to choose a lower fan speed to lower the air noise and static pressure. However, remember that this hack is only effective when the fan speed was initially too high.

Lowering the speed when the system was properly set up may lead to insufficient airflow or a lack thereof throughout your home.

Extra Ductwork

While equipment can be properly sized, the ducts can be too small to accommodate the volume of air. It’s a common issue. When this occurs, adding ductwork can significantly reduce the static pressure, making your system quieter.

You can have a larger duct installed in the reachable area around your furnace or blower to elevate the size of your supply and return plenums.

Incorporate a Bypass Duct

With several zones housed under one system, it’s no secret that adding a bypass duct that alleviates pressure within the system and diminishes noise is no easy feat.

Expand or Add Registers and Grilles

There’s no denying that most homes lack sufficient return air. Boosting the size of an existing grille or adding new returns is a foolproof way of decreasing static pressure and aiding in the airflow of your system.

Furthermore, it can reduce noise. As deemed necessary and whenever possible, you can also incorporate new supply registers into your ductwork or boost the size of current supply registers.

Substitute Existing Grilles and Registers with High-Velocity Models

At times, the type of grilles and registers you have are to blame for the loud air noise. Replacing them with high-velocity options can facilitate reduced static pressure coupled with increased airflow.

Elevate to a Variable Speed Blower

If your HVAC system is due for a replacement, then you’re in luck. With the assumption that you choose a new system with a variable speed blower, it’s almost guaranteed to be quieter than the generic blower you’re getting rid of.

The reason is that furnace fans or blowers of variable speed typically function at the low setting for more consistent airflow in your home compared to the classic off/on system that you’re used to. The fan speed differs based on the heating or cooling load. However, the fan functions at lower speeds for the most part.

Furthermore, with less air flowing through your ducts, it doesn’t come as a surprise that the noise levels are considerably lower. You’ll still know whether or not your system is functioning as it should.

After all, your comfort level is the giveaway. Nonetheless, you might not hear its operation unless you’re in earshot of the supply register. In some systems, variable speed blowers are impressively quiet.

Flexible Ductwork vs. Hard Pipe

Expert checking the duct
Source: Serenethos

With all other factors being equal, flexible ducts are quieter than their hard pipe counterparts. After all, air circulation through metal is louder. Compared to flexible ductwork that lacks bends, obstructions, or kinks, you’re likely to hear more noise with hard pipe ducts.

Given that hard pipe ductwork is less susceptible to bends and kinks, it’s typically more suitable for airflow. Contrarily, flexible ductwork is more prone to bends and kinds which means, it presents more points of failure for airflow.

In a nutshell, flex ducts translate to possible airflow issues coupled with less noise, whereas hard pipe ducts mean fewer airflow problems and increased noise. It’s a catch-22. Nonetheless, that doesn’t imply hard pipe ducts are constantly loud. With the assumption that they are well-sized for your system and home, you’re likely to hear minimal noise.

Therefore, if you have a variable-speed blower, that’s undoubtedly the case. Keep in mind that hard pipe ducts are typically noisier than their flexible counterparts, but there are always exceptions to the rule.


Armed with the insight into how to quiet noisy ducts, keep in mind that the rattling usually points to a bigger problem. Once you fix the underlying issue, the noise goes away, after which you can enjoy some tranquility in your home.

Pesky HVAC systems, air duct problems, and a noisy air vent will be the least of your concerns as you unwind with a book, your favorite tunes, or a movie.

Frequently Asked Questions

What does a popping noise in the air duct mean?

If you hear a popping noise in the air duct, it is typically caused by the movement of the duct walls because of pressure changes. For example, hot air makes the ductwork expand, while cold air makes ductwork contract. To fix the popping noise in your HVAC ducts, you need to insulate the duct or replace the duct.

What kind of soundproofing material can I use to quiet noisy ducts?

To help quiet a noisy air duct, you can consider using a duct silencer. An HVAC duct silencer is engineered specifically to reduce the noise that is carried along through the ducts or the noise produced by the enclosures. It is also known as a sound attenuator and is most often used in more industrial settings to help tone down unwanted noise.